EEVblog #315 - Korad KA3005P Review/FAIL - Page 1
Forum section: electronics / general

author: EEVblog
author_rank: Unknown
timestamp: July 18, 2012, 04:20:08 am
content: Dave.

author: Psi
author_rank: Super Contributor
timestamp: July 18, 2012, 04:33:48 am
content: I know that beeper sound, it's using a beeper that requires the micro to generate the tone. (They're cheaper than beeper with internal tone generators)When you try and generate the ~2kHz by setting/clearing the mcu output pin in software other interrupts will semi-randomly delay the set/clear commands and you get a sound that's dirty like that.To avoid it they need to use the dedicated hardware timer output pin on the mcu so the tone generation happens independently.(or a beeper that does the tone generation itself)

author: snoopen
author_rank: Contributor
timestamp: July 18, 2012, 05:36:12 am
content: Wondering if you'd recommend this over the similarly priced Jaycar lab supply? Looks like they both have an overshoot issue.This is the one:http://www.eevblog.com/2009/09/11/eevblog-30-jaycar-bench-lab-power-supply-review/I recently bought the Jaycar supply, but it's unopened in the box... Thinking I could take it back and get the Korad for the extra $40 or so.

author: snoopen
author_rank: Contributor
timestamp: July 18, 2012, 05:41:44 am
content: Hmmm on second thoughts, I actually finished watching the last 5 mins of the review. Can see why you say FAIL! :O Oh wells!

author: Erwin Ried
author_rank: Regular Contributor
timestamp: July 18, 2012, 05:46:34 am
content: It seems M5 memory led is the LOCK led:http://www.ebay.ca/itm/KORAD-PROGRAMMABLE-PRECISION-VARIABLE-30V-5A-DC-POWER-SUPPLY-DIGITAL-LAB-GRADE-/110888868115?pt=BI_Electrical_Equipment_Tools&hash=item19d17dd913by the pictures

author: nitro2k01
author_rank: Frequent Contributor
timestamp: July 18, 2012, 05:55:08 am
content: Playing devil's advocate here, but could it be that you've swapped the power input and output on the logic board when reassembling it after the teardown? They seem to be using the same connector.This way you might for example have blown the ever so beefy protection diode across the shunt, and later voltage regulation transistor or something else.

author: dda
author_rank: Contributor
timestamp: July 18, 2012, 06:14:49 am
content: Dave did get into M5 at one point in the vid, but he didnt make any note of it

author: Psi
author_rank: Super Contributor
timestamp: July 18, 2012, 06:18:07 am
content: Quote from: dda on July 18, 2012, 06:14:49 am"M5" is Mission Impossible mode for MI5 operatives.This unit will self destruct in 5 seconds.

author: dcel
author_rank: Regular Contributor
timestamp: July 18, 2012, 07:37:11 am
content: DaveAn autopsy would be nice so we can see what failed and showcase your troubleshooting skills for all the young players.Chris

author: hans
author_rank: Super Contributor
timestamp: July 18, 2012, 08:28:44 am
content: Honestly, a follow-up would be funny. It would humiliate this PSU even more.I wasn't impressed with the teardown stage. Everything is 'there' to get a DC programmable PSU, but it seems rubbish built. Uncleaned PCB's, random holes drilled, poor soldering, weird R2R DAC (apparently PCB space and SMT parts placing is free for them) and overall shitty stuffThat you have killed it with a 'constant resistance' is too funny. That's like connecting 1 ohm on a 24V output, you should get 5V @ 5A right..I think the very odd load transients are maybe due to it's unusual current shunt. Seen it in the teardown? It's like more like an inductor of several tenths to hundreds of uH. I would be interested in setting the load transient at turn-off (at least as important as turn-on), will it overshoot due to the inductor?But unfortunately it's died already

author: David Aurora
author_rank: Frequent Contributor
timestamp: July 18, 2012, 08:30:36 am
content: My curiosity is killing me here haha, I'm dying to know more about the death of this thing. Did any magic smoke actually escape, or is it software related?

author: Physics_Dude
author_rank: Newbie
timestamp: July 18, 2012, 09:00:22 am
content: Something like this happened to me a while ago with a basic 30v/8A switched mode DC power supply. I think it was a Mastech brand, but I could be wrong. I was using it to power an innocent little project at 6 volts with only a few milliamps, when suddenly at random, the power supply decided to dump a steady 56 volts through the little thing and kill it!Further testing relieved that the power supply was also in a consent current mode of around 8 amps. None of the output adjustment knobs had any effect on the output voltage or current.It was replaced soon after by a more preferred power supply, but I decided kept the broken one, it seemed quite reliable for supplying the 55-56 volts that it was stuck at.However, after weeks of abuse on the old one, while I was using it under a fairly heavy load for some extend period of time (the device lacks a cooling fan and will get hot), I heard a few clicks of the relays, and wouldn't you know it, it went back to its normal, advertised operation. I had my full voltage and current limiting controls back too!I don't use this zombie-like power supply for any serous projects anymore for obvious reasons. It also recently decided to get stuck again in consent current mode at 8 amps. I still have full control over its output voltage though.I only mention this because Dave seems to have fallen in a similar predicament where his power supply seems to send out its full current capacity at a higher then rated voltage (42.3v at first).

author: Scopeman1
author_rank: Contributor
timestamp: July 18, 2012, 09:11:03 am
content: Just been to TRIO's website. How well do you know these guys Dave? Are they any good? Agilent all over the place.I saw this on link below...... does not look too bad for the money, and they are local in Sydney. It's better value than the Jaycar. It is a triple output for less than the Jaycar dual output cost even with GST & freight!!http://triosmartcal.com.au/dc-bench-supplies/2432-atten-aps3003s-3d-dual-power-supply-0-30v-3a.htmlThey have a 150W basic bench supply for $99http://triosmartcal.com.au/dc-bench-supplies/2631-qje-ps3005-bench-power-supply-150w-0-30v-0-5a.htmlIt can't be a linear for that price.As for cheapie scopes, I see they are selling the same scope as Jaycar for almost half the price as Jaycar !!! WTF!! They can't be ripping people off at that price or .... Mr. Jaycar is charging us too much for convenience or?http://www.jaycar.com.au/productView.asp?ID=QC1932jaycar $599 inc GSThttp://triosmartcal.com.au/2195-siglent-digital-storage-oscilloscope-25-mhz-bandwith-4-channel.html= TRIO $298 ex-GSTIt's the same scope isn't it? Can you confirm?

author: wiedehopf
author_rank: Newbie
timestamp: July 18, 2012, 09:30:51 am
content: Quote from: nitro2k01 on July 18, 2012, 05:55:08 amI think the power cable leading from the control board to the output ist to short to connect it to the input on the control board. Dave would've noticed the cable being tense, so it's not an error i think he would've made.But i guess we'll see soon enough when he tracks down the error.

author: EEVblog
author_rank: Unknown
timestamp: July 18, 2012, 09:35:33 am
content: UPDATE: Triosmartcal have withdrawn it from sale, and Korad are investigating...Dave.

author: PChi
author_rank: Frequent Contributor
timestamp: July 18, 2012, 10:22:04 am
content: Thanks for the video tear down and test.It might have foldback on the current limit which may be why it was giving inconsistent results with the constant power load.I am guessing that the output on/off switch just controls the Power Transisters which may have failed Collector Emitter short circuit. The output stage might rely on never having to drive a short circuit when the transformer tap is at the maximum voltage for survival (even with some form of foldback limiting). Possibly Korad need to check the Safe Operating Area of the output transistors. Also cheap power transistors can be unreliable.

author: amyk
author_rank: Super Contributor
timestamp: July 18, 2012, 10:24:48 am
content: I would've preferred a relay-switched output. Those usually do not fail short (unless the contacts have overloaded and welded together.)

author: T4P
author_rank: Super Contributor
timestamp: July 18, 2012, 12:30:52 pm
content: Quote from: amyk on July 18, 2012, 10:24:48 amThe golden method of switching voltages in and out without a physical switch but obviously... dickheads-designersand yes a crowbar is better

author: Greg J
author_rank: Regular Contributor
timestamp: July 18, 2012, 01:18:59 pm
content: Chinese quality. I don't think anyone was hoping this will work for this price.Even their website is one big fail.

author: Stephen Hill
author_rank: Regular Contributor
timestamp: July 18, 2012, 01:28:00 pm
content: Quote from: Greg J on July 18, 2012, 01:18:59 pmWhat's wrong with their website?http://koradtechnology.com/en/

author: Bloch
author_rank: Unknown
timestamp: July 18, 2012, 02:26:01 pm
content: Quote from: Stephen Hill on July 18, 2012, 01:28:00 pmHard to read ?

author: Rufus
author_rank: Super Contributor
timestamp: July 18, 2012, 02:26:14 pm
content: It is pretty obvious the main series regulating transistor failed short circuit providing an unregulated supply from whatever the transformer tap relays have selected.When you start putting effective shorts on the output with the supply set to high voltage the pass transistor experiences maximum stress until the relays tap down the transformer. Probably an SOA failure because the output transistor is grotty or marginally specified.On 'funny things going on' understand a constant power load with no volts applied is trying to be a short circuit so when you switch a supply on to it the supply ought to go straight into current limit and stay there delivering insufficient power.The load probably has a minimum turn on voltage setting/option where it won't start drawing current till the voltage reaches that value as a workaround for the problem.When you turn on a constant power load with a supply already connected it is a race between the load reducing the current draw and the supply going into current limit.

author: slburris
author_rank: Frequent Contributor
timestamp: July 18, 2012, 02:49:19 pm
content: I almost wonder if they are doing something stupid, like implementing the controlloop in the processor, given the strange ramps at turn on.Of course you would get terrible transient response doing it that way, butI've seen designs on the net doing just that.Scott

author: firewalker
author_rank: Super Contributor
timestamp: July 18, 2012, 03:15:52 pm
content: The machines that checks if a chip passes all the tests what does with the rejected ones? Maybe makes a mark on the surface? Just saying... You know, sanded chips...Alexander.

author: Electr0nicus
author_rank: Regular Contributor
timestamp: July 18, 2012, 03:56:45 pm
content: Most high current linear power supplies use more than one series transistor. They are usually paralleled and to eliminate thermal runaway there are current balancing resistors used. Maybe there are no, or insufficient current balance resistors used in this PSU, so one transistor gets most of the current and self destructs, so the other transistor also gets the maximum current and gets destroyed too.

author: pickle9000
author_rank: Super Contributor
timestamp: July 18, 2012, 04:26:07 pm
content: I think the biggest problem here is the level of "cheaping out". 3 or 4 shortfalls and the product hits the floor. The manufacturer could turn this into a win by fixing the problem and then sending out a few copies to be reviewed. I would certainly buy a product that has been redone and brought up to snuff.The fact that they cut corners, case, finish, design, lack of cleaning and so on are an issue but if it fails out of the box your name is mud. The unit has a good front panel layout, simple to operate form factor, so a win there.Looking at the web site you can see that most of their product line is based around a variant of this unit. That being the case I hope they have the incentive to fix it.Is this another example of Chinese manufacturing cheaping out. Yes, and extra 10 bucks per unit and this may have been an acceptable product. I'm not saying great but OK for the money.Can you blame the engineer, the build team, management. Yes all of the above....mike

author: T4P
author_rank: Super Contributor
timestamp: July 18, 2012, 04:28:59 pm
content: I usually side with HK companiesbut it all changed with this eventnah i'm kidding, just not this one. For now.

author: gxti
author_rank: Frequent Contributor
timestamp: July 18, 2012, 05:18:40 pm
content: I agree that some of the early weirdness during testing is probably due to the control loops of the load and the supply interacting in non-obvious ways. But then the thing burnt itself out, no excuses there!

author: LaurenceW
author_rank: Frequent Contributor
timestamp: July 18, 2012, 07:11:33 pm
content: Well, by the time I got here, others had already made the same points! But I concur:It looks like the design uses a software loop for voltage stabilisation, hence the ramps (up and over) while the software catches up. NEARLY ALWAYS BAD.I wonder if your earliest glitches when the output died were software related?The soft on/off switch will probably work by simply turning off the base drive to the (two) main series pass transistors. Since current continues to flow, that suggests fried output devices (or possibly fried common driver).The internal voltmeter probably maxes out at around 36V (was it?) because in normal use it would never even need to go that high. Under fault conditions, the output rises above this to the main supply cap figure, however. And at 57V, that seems a bit OTT anyway for a 3OV power supply.I doubt that encoder is "optical" - just a simple two-switch affair. CHEAP!I didn't like the quality of the PCB design, at all. Not laid out by a seasoned designer. Inconsistent use of vias, track widths and routing styles.The discrete D>A converter seems bonkers. Surely there are plenty of fine chip solutions which would use less components, hence less PCB real estate, assembly time, etc.?SMUG MODE : I've just bought me a new end-of-line TTI 3 channel power supply PL330TP (30v x 3A). It is built like abrick dunny(as I think the antipodeans would say). The only problem with it is the HERNIA it gives me when I try and pick it up. It will still be going strong when I am long dead. Pays yer money. I might do a teardown one day.

author: hans
author_rank: Super Contributor
timestamp: July 18, 2012, 07:46:20 pm
content: All power supplies fail.. At college we had an Agilent 3630A triple output. We used it to power a transistor signal amp of +/-10V.There was an unit that was faulty on -10V, where it would ramp up to -30V and sometimes stay there (the panel meters indicated , but the scope confirmed). So, yeah, that kinda sucks if you make fireworks TWICE with tantal caps of 16V as decoupling. Oh well. At least we made fun of each other when caps blew up on the negative rail (ah you screwed that up mate!) and then it happens to myself the day after.Then we figured out the PSU was bad..The overall quality of this supply is really crap. When I saw I thought, yeah, it will do 30V/5A for a few moments and then explode in flames. Not built to last. The PCB's are dirty, soldering is bad, bodges everywhere, weird case construction, weird DAC, the current shunt looks more like an inductor (dave, can you measure it?- maybe it explains a part of the weird load transients, unfortunately it's now fried but the turn-off response would be interesting too), weird holes/isolation idea.Furthermore, an R2R dac is a horrible concept. If you read the WIKI, you need to have matched resistors for that. Well, you can take them from the same batch, but as Dave showed with his batch measurements some time ago: 1% resistors measured over a range of 1000s will have a variation of 0.5% - 1%. I see they stacked up 16-bits for current and voltage. That's just a bullshit thing. I bet the actual accuracy isn't that great. Furthermore, if you control 3000 to 5000 counts, why do you need it?Apparently PCB space and assembly is free there!Furthermore, the relay switching seems too slow. Too little capacitance? 6800uF at 5A & 100Hz isn't a great deal.I can understand them switching the relays.. They of course look at the live output voltage (after current limiting) and make sure the voltage difference across the transistor isn't too large. Those other cheap PSU's recently linked here do the same, and basically have the same problem. I've encountered this a few times on a rather large buck-boost LED driver.I basically tried the same abuse. Put the output at 30V/5A, and turn on a 60W load with 15A inrush currents. The output drops to 3V/5A, and that's it. The PSU didn't die, though.

author: ivan747
author_rank: Super Contributor
timestamp: July 18, 2012, 08:42:24 pm
content: Also rebadged as a "Quakko" supply (quack)http://www.mastechpowersupply.com/dc-power-supply/linear-power-supply/programmable-dc-power-supply-32v-5a-lab-grade-hy3005dp/prod_49.html

author: Bored@Work
author_rank: Super Contributor
timestamp: July 18, 2012, 08:54:52 pm
content: Quote from: EEVblog on July 18, 2012, 09:35:33 amThe thing I am asking myself is what was the procedure Triosmartcal used to decide to add it to their offerings?Did they get a sample from Korad? Did they at least open it? Was the sample a special or from the normal production? Did they at least checked one when they took delivery of the batch they ordered? Did they check the manual for completeness?QuoteSure. Wana buy a bridge?

author: ivan747
author_rank: Super Contributor
timestamp: July 18, 2012, 08:55:13 pm
content: Quote from: Erwin Ried on July 18, 2012, 05:46:34 amI believe Dave received an early version.

author: ivan747
author_rank: Super Contributor
timestamp: July 18, 2012, 09:12:16 pm
content: Quote from: slburris on July 18, 2012, 02:49:19 pm+1

author: Electr0nicus
author_rank: Regular Contributor
timestamp: July 18, 2012, 09:58:47 pm
content: The white residue comes from cleaning the PCB with an acetone like solvent. Acetone breaks up the molecular bonds of the flux leaving back this white substance if not washed off thoroughly . This indicates that they actually don't wash the PCBs in the solvent, but rather only dipping it into. When the solvent dries off, the flux is still there, with the difference, that it is now a white powdery substance, due to the broken up molecular bonds. You can easily brush it off using an old toothbrush f.e. I know that, because I myself use acetone the most time to clean my homemade PCBs. Of course, you have to know, what plastics are on the board, because f.e. PVC gets attacked by the acetone. But apart from that, almost all plastic components on a PCB are acetone tolerant.

author: wiedehopf
author_rank: Newbie
timestamp: July 18, 2012, 10:06:04 pm
content: Regarding:Thread Original Video at 18:30Once the Power Supply is in CC Mode, the constant power load will further reduce it's resistance and hence the Voltage across the load drops to near nothing.How it gets there is beyond me.Perhaps the initially low load resistance sucks dry the power supplies capacitors and when recharching them the supply goes into CC mode. Just a guess.But that is not sth bad i'd say. Where in real life do you have a constant power load?The breakdown on the other hand is really bad news. And escpecially the Over Volt Protection really works like a CHARMEdit: grrrr ... auto youtube embedding destroyed the timecode so i took it out

author: Electr0nicus
author_rank: Regular Contributor
timestamp: July 18, 2012, 10:24:38 pm
content: Quote from: wiedehopf on July 18, 2012, 10:06:04 pmThere are power supplies out there, which generate a overvoltage condition, that is not so obvious like on the Korad PSU. I f.e. have a ELV PS9530 30V 10A PSU and one day I discovered mostly by accident, that it puts out a huge overvoltage pulse when switched off (proper mains power switch).http://www.mikrocontroller.net/attachment/70639/PS9530_KM_G_071030.pdfThis phenomenon only occurred when the relay was switched on and thus the two transformer taps were connected in series to deliver a output voltage >15V. I found out, that it was actually a design glitch with the freewheeling diode of the relay, thus the control circuitry was influenced and switched on the serial pass transistors completely, delivering 40V to the output for at least 20ms. I found a solution to prevent that and emailed it to the company, which has designed the PSU. But they weren't even interrested in solving the problem and said that "because nobody had ever complained yet/found it out, they wouldn't bother correcting the mistake they made". Absolute dickheads.But end of rant! What I want to say, is that even if you buy a higher priced PSU, (mine costed 359€/425AUD) you are not immune to such problems.

author: free_electron
author_rank: Super Contributor
timestamp: July 18, 2012, 10:51:55 pm
content: Quote from: Electr0nicus on July 18, 2012, 09:58:47 pmcleaning pcb's in acetone is not done. acetone eats too many plastics. the displays for example would melt ... same for at exle of the rotary encoder ..this residue is most likely water soluble flux that has not fully saponofied and washed away.water soluble flux is hygroscopic and will yield the classic white soap-scum appearance if not washed properly.

author: Electr0nicus
author_rank: Regular Contributor
timestamp: July 18, 2012, 11:07:07 pm
content: Quote from: free_electron on July 18, 2012, 10:51:55 pmThanks free_electron!I didn't know that up to now.As I wrote, I use acetone to clean my PCBs, when there are no sensitive plastics on the board. Then I get the same type of white residue, but it's not soapy but powdery.If this residue is hygroscopic, then I assume it must be a acidic or basic? Or I'm completly wrong. So if it's a base or acid, then this will be conductive soapy layer on the whole board, which can't be good

author: Denno
author_rank: Newbie
timestamp: July 18, 2012, 11:12:50 pm
content: Almost certainly a blown pass transistor in the series regulator. Be interesting to see the part number on the MOSFETs to see if they are under rated. The is why some form of crowbar output protection is employed in better engineered supplies. If the output goes higher than some threshold then an SCR or transistor shorts it to ground and blows the supply fuse. Supply still needs to be fixed but does not take your circuit with it.The test with the constant load of 50W where output was dropping to 0.2 volts was understandable at the electronic load would present an almost dead short when the supply output was switched on. A better test is to use the load switch on the dummy load to turn the constant power load on and off. This way the electronic load sees the set supply voltage and only switches in the appropriate current load for the power setting.

author: Bloch
author_rank: Unknown
timestamp: July 18, 2012, 11:22:08 pm
content: Quote from: Denno on July 18, 2012, 11:12:50 pmWhy not a relay ? Is it not fast enough ?

author: JoannaK
author_rank: Frequent Contributor
timestamp: July 18, 2012, 11:38:53 pm
content: Quote from: EEVblog on July 18, 2012, 09:35:33 amNext time.. Try to get some smoke out of it

author: free_electron
author_rank: Super Contributor
timestamp: July 19, 2012, 01:01:51 am
content: Quote from: Bloch on July 18, 2012, 11:22:08 pmA relay is slower than an SCR to kick in but the main reason lies elsewherea relay needs power to energize and close itself... shorting the power rail .... removes the power from the relay ... so that relay would become buzzer .... until the fuse popsunder a certain voltage the relay will also not have enough megnetic pull to close the switch...an SCR is triggered on its gate and stay s in conduction until the current through it has fallen under the hold current. this hold current can be very low.So: fire the SCR and it stays in conduction until the fuse is blown and the capacitors in the circuit are discharged far enough that the current has dropped to a few milliampere. Then it comes out of conduction . the voltage across the scr can be 0.1 volt . it doesn't care as long as there is current flowing it stays on.

author: TRIO_Smartcal
author_rank: Contributor
timestamp: July 19, 2012, 01:26:37 am
content: Greetings and thanks for all the feedback.Firstly yes we have withdrawn this from sale until we get to the bottom of the failure. To answer the previous question about what process do we use to decide what to sell, well we have a process and this passed it.We got two samples a 30V 5A and a 60V 2A. As an ISO-9001:2008 accredited company, a structured product introduction process is mandatory. We look much further than just the build quality. We look at support scenarios and how we and the supplier can deal with them so :- what is the warranty?- Can we repair locally?- Is there a calibration procedure?The samples do get pulled apart. For example the white residue on the boards was known to us, we've seen it on more than one suppliers' boards and it has never been a reliability issue.For the price as Dave says the build quality was aceptable and we liked the user interface too.We also have already fed back the incompletness of the manual plus we'd like to see the programming commands in there too.Our performance testing entails putting a product through our NATA accredited calibration lab to make sure it meets its specifications which these supplies did. (NATA is similar to UKAS , NVLAP etc) Thanks to Dave's dynamic (in more than one sense of the word) testing of the supply a potential weakness has been exposed that the placid conditions of a Cal lab would not reveal. The product was immediately pulled from sale as we will not sell a product we don't have 100% confidence in, and after Dave's review we have our doubts on this one until we get a manufacturer recommendation and/or rectification proces. We are certainly not scared of putting a product through an EEV Blog tear down and product review as the result can only be beneficial for customers, us and of course the manufacturer that will need to act on the findings so that the market gets better products and we get happier customers.We try to offer two classes of product and if you visit our web sitewww.triosmartcal.com.auyou will see this in action. We offer world class brands like Agilent, but sometimes that's not what people need or can afford. Wants and needs are different. So for folks with budget constraints, or simply needing something that does not have a world class brand label on it we try to offer lower cost, value-for-money reliable products that do what they are supposed to do. Plus we need to be able to support our customers locally after they have bought something from us. Our customers are everything to us, it does not matter how good our products are without happy customers and good staff to look after them we won't be here.There is a formula used in marketing-speak that is very simple but very true:Value = (Performance/Price) + Service .........OK I know the brackets are redundant but most marketers are not engineers. Many people do not consider service when buying a product but it is an integral part of acquiring and owning a product.The other true marketing statement is that "you get what you pay" for. Well it's mostly true unless you are being ripped off. So our challenge is to choose products that meet these criteria. We thought this power supply met our criteria and until we are sure it does, it is withdrawn from sale. By the way we know it is cheaper in the USA. That is to do with volumes when purchasing, freight costs, customs clearance etc. We set our prices to be competitive, offer value for money and provide an adequate return for the company so we are still here for you if something does go wrong. It is all a big balancing act. Proof of this can be seen in another post I saw on here comparing our price on a 25MHz digital scope to a much larger company's price here in Australia. We are almost 50% less expensive and at that price we meet all our criteria necessary to take that scope to market. (thanks to whoever did that for pointing that out).Ultimately you pay your money and make your choice. At $199.00 +gst here in Australia it is competitively priced for a locally sold and locally supported product. If we find out afterwards that something does not perform as initially expected, we won't sell it. We have sold a few of these and have not had any returns. Nevertheless we did not know it could not handle the Dave treatment and now that we do know, it is off-sale. For folks that want a main brand, the big-guns are coming down in price. You can pay $360+gst and get an Agilent U8001A with 30V 3A. It is an excellent product for the price. Maybe Dave should do a tear down on one of those for comparison.Anyway I hope that answers your question and also why we have withdrawn this product from sale. Until we know the reason for the FAIL and the preventative fix it stays off-sale. Dave has full permission to rip it to bits to find out what went wrong as it seems there is quite a bit of interest in this. Just don't drive over it please Dave ;-)

author: grenert
author_rank: Frequent Contributor
timestamp: July 19, 2012, 02:58:56 am
content: Unless you really need the programmability or the digital display, I think many people would do much better (at the same price) with an old tank of a power supply like this one:http://www.ebay.com/itm/HP-6227B-Dual-DC-Power-Supply-W-Option-40-0-25V-0-2A-30-Day-WARRANTY-/300743973561?pt=LH_DefaultDomain_0&hash=item4605bcdab9There will certainly be no funny business with it!

author: amspire
author_rank: Super Contributor
timestamp: July 19, 2012, 03:18:20 am
content: Quote from: grenert on July 19, 2012, 02:58:56 amHey, that is my power supply!It is a good supply, reasonably compact (compared with other supplies of the same vintage) and no fan to annoy you or to fail. Proper independent thyristor based overvoltage circuit for when you are testing that board you cannot afford to accidentally damage.For average use, I prefer the moving coil meters to the digital readout. I like having a coarse voltage and current control that can go from 0V to maximum in a single twist.Richard.

author: ivan747
author_rank: Super Contributor
timestamp: July 19, 2012, 03:51:48 am
content: Quote from: Bloch on July 18, 2012, 11:22:08 pmIt's too slow. About 3 orders of magnitude slower than a good transistor. Relays take milliseconds to switch. You don't want your $2000 dollar 1.8V prototype being exposed to 30V, do you? It is not uncommon to see transistors switching in tens of microseconds. Although, I reckon the slowest component in a overvoltage protection circuit would be the fuse.

author: Alexei.Polkhanov
author_rank: Frequent Contributor
timestamp: July 19, 2012, 04:06:36 am
content: I have BK PRECISION 9110 on my table right now. I got it for $299 from Newark. I connected it to 10 ohm resistor, set current limit to 20mA, voltage - 10V and pressed ON button - result is what seems to me rather large overshoot in voltage (see attached photo). This is is the only lab supply I have right now. It is a new device, good brand, so I am not sure if it is so unusual to see large overshoot on these supplies in current limiting mode, unless you want to spend over $2000.After all what matters, in my opinion, is power delivered to connected device over set limit in watts not how high voltage is or in other words 10v overshoot for 100ns is better than 500mV overshoot for 100ms, right?

author: Scopeman1
author_rank: Contributor
timestamp: July 19, 2012, 04:36:43 am
content: That looks worse than the KORAD. Also BK Precision re-badge other products, like the Siglent Scopes, the Atten spec-an, Protek HH-spec-an and some of the power supplies look similar to those on Extech's website. It would be great of someone started a cross-reference for all this re-branding nonsense so we can buy from the OEM and cut-out the big-name companies adding the brand name and price tag. As for Alexei's power supply, does it say "made in China on the back panel?"

author: EEVblog
author_rank: Unknown
timestamp: July 19, 2012, 04:58:12 am
content: Quote from: TRIO_Smartcal on July 19, 2012, 01:26:37 amThanks for the detailed reply Charles.I will try and find some time to investigate what failed on it...Would of course be nice if Korad released the schematic!Dave.

author: T4P
author_rank: Super Contributor
timestamp: July 19, 2012, 05:17:33 am
content: Quote from: Scopeman1 on July 19, 2012, 04:36:43 amMost of the extech's are manson PSUs tooBut the best way to OVP is a independent SCR adjustable monitoring circuit

author: Bored@Work
author_rank: Super Contributor
timestamp: July 19, 2012, 05:38:02 am
content: Quote from: TRIO_Smartcal on July 19, 2012, 01:26:37 amIn other words, you sailed hard on the wind, but this time the wind got the upper hand. Time to change your process to apply a more conservative pass criteria?QuoteCan we skip that ISO thing, please? After decades in the industry, taking part in multiple accreditations, and having had to game the system daily for long periods of time I have nothing good to say about it.QuoteThe thing with the flux residue is you can't know its long term effects, e.g. if that particular residue is corosive over time. You just don't know the manufacturing process and what they used.And lets just say, as a calibration company you should have got very, VERY nervous about that DAC. That is your core bussines.

author: free_electron
author_rank: Super Contributor
timestamp: July 19, 2012, 06:07:47 am
content: Quote from: Bored@Work on July 19, 2012, 05:38:02 amISO : The process can be total crap , as long as it is described in detail and meticulously followed.. ISO only verifies you:1) have a process2) follow it3) can track itas for the process itself : that may be 'put on tin foil hat , chant rama rama hare hare, put left big toe in right ear and sign form 123-a at the dotted line.'

author: Scopeman1
author_rank: Contributor
timestamp: July 19, 2012, 06:28:50 am
content: I disagree with Mr. Bored not having much good to say about ISO, many others do have good things to say and look for ISO accredited vendors. It forces a process and a standard on to a company. Agreed that compliance is a pain in the a$$ but it sets a level people can judge a company by. If Mr.Bored@Work fudged it or worked around it then he's only fooling himself and anyone who did business with his company. As for putting on a tin foil hat and chanting rama-rama-guru as part of a power supply test, I suspect most ISO accredited companies probably choose more relevant criteria as part of their processes.We buy based on the performance spec. and the price, plus previous experience with a vendor. Charles' formula about value, performance and service makes sense. If they test to the performance spec it is sold under and it meets that spec and they can support it if it goes wrong then that seems reasonable and I'd buy from them. The fact that they stopped selling the item immediately is also good. It shows they put quality, and not putting potentially flawed products into the market before making profit. Even big names like Fluke etc issue recall notices and withdraw products from sale if there is an problem with them so what Trio has done is the right thing to do.Mind you I agree on the testing process, perhaps more a few more real world operational tests in addition to a cal-lab performance verification might uncover this sort of thing before Dave gets his hands on it. I think they sell electronic loads too so maybe they should test both together ;-). Probably though a batch test would be the way to go when something like this is uncovered to see if Dave got the lemon or a normal product.No opinion on the DAC really, if it does its job as Dave says what the heck!!! I hope Dave does a tear-down to find the problem with it. Anyone want to start a poll to guess the fault?

author: dda
author_rank: Contributor
timestamp: July 19, 2012, 06:39:28 am
content: I think people are being a bit hard on our scope-crushing friend. He isn't in the business of selling something faulty on purpose. If Dave hadn't busted it before he finished the review he probably would have given it a conditional thumbs up. And it wasnt completely faulty at the beginning.Chillax bros.

author: Bloch
author_rank: Unknown
timestamp: July 19, 2012, 06:53:16 am
content: Quote from: EEVblog on July 19, 2012, 04:58:12 amI have heard rumors that they are in process with striking out all component values with a thick black marker

author: Unknown
author_rank: Unknown
timestamp: July 19, 2012, 07:15:37 am
content: Quote from: Bored@Work on July 19, 2012, 05:38:02 amFor a sub $200 supply? Guess you haven't been taking you reality pills for sometime, eh Bored? Trio Smartcal have taken all appropriate action. Did you expect weeks of destruction testing?QuoteWhy? It's the tool of delight for desk cowboys like yourself. A long winded way of saying all care, no responsibility.QuoteIf it's corrosive? If it radioactive it could sizzle your gonads too, however if is very much the operative in either wild guess. Seems you've avoided reading the highlighted portions of the suppliers comments, it certainly appears they have a lot of prior experience applied in their judgements .QuoteWho the hell seriously calibrates (or has calibrated) a sub $200 instrument? that's hairy palm stuff! An occasional quick tweak would satisfy anyone sane.

author: amspire
author_rank: Super Contributor
timestamp: July 19, 2012, 07:35:24 am
content: Quote from: Uncle Vernon on July 19, 2012, 07:15:37 amThe thing I love about ISO-9001 is you can make the lowest quality and least reliable piece of gear in the industry, but as long as the documentation correctly describes this low quality unreliable design and construction, you are a fully complying with the 9001 quality standard.You can make the best and most reliable piece of gear in the world, but if you do not follow the correct paperwork procedures (i.e. the procedures you committed to when you set up ISO9001 for the firm) when you identify and correct problems, you are failing 9001.If your ISO9001 implementation specifies a procedure where all reports of problems are entered on the correct form with the correct number and then shredded, that would probably be fine for ISO9001 as long as you actually shred all the forms, and record the shredding in another document. In this case, if someone instead reads the forms and corrects the problems, that would be an ISO9001 quality control failure for the firm.Richard.

author: ejeffrey
author_rank: Super Contributor
timestamp: July 19, 2012, 07:54:15 am
content: Quote from: Scopeman1 on July 19, 2012, 06:28:50 amNo, it doesn't. Without knowing the documented practices, ISO certification only tells you that a company likes paperwork. I don't think it is bad or worthless per se, but it should be an internal matter. If ISO9000 certification helps you organize the internal operation of your company and improve quality control, go for it, but it isn't really anything your customers should have any reason to care about. It is like if you told your customers that "We only use full spectrum fluorescent bulbs in all our offices to maximize worker productivity" ISO9000 is certainly no substitute for good quality control practices.That said, I don't expect much from a distributor of a $100 programmable power supply. That falls squarely in the "you pays your money and you takes your chances" category, and anyone who pays that little for a power supply should know it.

author: Alexei.Polkhanov
author_rank: Frequent Contributor
timestamp: July 19, 2012, 08:07:33 am
content: Quote from: Scopeman1 on July 19, 2012, 04:36:43 amNope, dos not have any indication where it was made - probably there was something on a box which I have disposed. I have opened it and inside it is all different from KORAD although front panel has some strong resemblance.Looking at Datasheet for Agilent E36XXA series which I may need to buy because I need dual supply with trackingTransient Response Time: "< 50 ?sec following a change in output current from full load to half load for output to recover within:" 10 mV 15 mV (15mV for more powerful versions).That is MICROseconds. My supply does not even have Transient Response Time in datasheet.

author: EEVblog
author_rank: Unknown
timestamp: July 19, 2012, 08:27:10 am
content: Quote from: Scopeman1 on July 19, 2012, 06:28:50 amI also could have lucked upon a particular load condition which causes the unit to fail, that may very well be next to impossible to find with normal acceptance testing. We just don't know unless more units are tested.QuoteMost likely a shorted pass transistor of some description.My guess would be it was being pushed outside of it's SOA (Safe Operating Area).The likely underspeced heatsink (without doing some calcs & measurement) won't help in respect.Given that Korad don't publish the performance curves of the scopes, the customer does not know the power limits over the voltage range. Without that info, you have to assume it can handle worst case 150W (30Vx5A) load at any output voltage and transformer tap. In practice, with linear supplies, it ain't that simple, unless they are overengineered like a brick dunny.Dave.

author: EEVblog
author_rank: Unknown
timestamp: July 19, 2012, 09:01:24 am
content: Official response from Korad (in part):QuoteQuoteSo there you go, under specced (or dodgy) transistors, surprise, surprise!Genuine high power transistors are not cheap, and have been scammed on the grey market for several decades now. Wouldn't surprise me if Korad got duped.Dave.

author: TradieTrev
author_rank: Contributor
timestamp: July 19, 2012, 09:06:58 am
content: Great to see Korad live up to the expectation one would expect using on a psu!

author: janoc
author_rank: Super Contributor
timestamp: July 19, 2012, 09:14:46 am
content: Quote from: EEVblog on July 19, 2012, 09:01:24 amHmm dodgy vendor selling gear with dodgy parts from who knows where. With something like a PSU that can deliver so much power, that is literally asking for lawsuit when it blows up in someone's face ...

author: hans
author_rank: Super Contributor
timestamp: July 19, 2012, 09:44:54 am
content: Quote from: EEVblog on July 19, 2012, 09:01:24 amIn that case they can sent a new production model (or maybe Trio Smart Cal has some) and give it some more Dave treatment?Well, yeah, pre production models can fail. You had the Agilent scope also failing with the extension card board. They fixed the issue and now it works fine. So I guess it happens all over the industry.

author: EEVblog
author_rank: Unknown
timestamp: July 19, 2012, 10:37:54 am
content: Quote from: janoc on July 19, 2012, 09:14:46 amWe do not know if they are dodgy parts, that's just speculation. They may very well be genuine parts, but accidentally installed the wrong type or something.Dave.

author: EEVblog
author_rank: Unknown
timestamp: July 19, 2012, 10:40:53 am
content: Quote from: hans on July 19, 2012, 09:44:54 amJust on my blog alone there is the Agilent 3000 scope, the Extech 505 meter, the Extech pen meter, the BK Precision LCR meter, and the Agilent U1272A meter (any others?)So yeah, it happens all the time. Most are never made public.Dave.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: July 19, 2012, 10:59:32 am
content: Quote from: EEVblog on July 19, 2012, 10:40:53 amAnd the Fluke EMC issue

author: TRIO_Smartcal
author_rank: Contributor
timestamp: July 19, 2012, 11:26:23 am
content: When we get a fix for this and an up to date production unit, Dave will get another to do his best to let the smoke out. When he does and IF it gets a thumbs up, we'll give it an extra years warranty at our cost. Until then it stays off sale.As for the ISO thing, I totally agree on the fact you can document any procedure, show compliance, prove it to an auditor etc..... But it simply comes down to the question " is the procedure relevant and beneficial to your business and will your customers benefit because you have these processes?" We believe it does.While a process that involves wrapping one's head in tin foil, while singing Hare Krishna with a toe in one's ear, be it your toe or that of an intimate friend, might be a process that is repeatable, documentable, auditable, and for some trolls perhaps an enjoyable process, strangely enough it's not one we use in the selection and supply of test equipment. Others might, we don't

author: Rufus
author_rank: Super Contributor
timestamp: July 19, 2012, 11:40:32 am
content: Quote from: Scopeman1 on July 19, 2012, 06:28:50 amJust lol - the only people with good to say about ISO 9001 are those making a living from it.ISO 9001 is widespread because like a virus and by design it is contagious, not because it does anything useful.Quote from: TRIO_Smartcal on July 19, 2012, 11:26:23 amAnd when the answer is yes but could be improved (as Dave appears to have demonstrated) ISO 9001 is going to make changing them more difficult and expensive.

author: poorchava
author_rank: Super Contributor
timestamp: July 19, 2012, 11:48:18 am
content: Hmm, I wonder if Korad is really going to remove the issue and use higher spec/ quality brand transistors will there be any way to tell bad and good versions apart? I wanted to buy that from Korad distributor here in Poland (they mainly deal in rework equipment like IR stations, BGA reballing stuff, soldering irons, chemistry etc) but now i guess I want to know how to tell if they are selling 'good' or 'bad' version (of course assuming that Korad will really do what they say and that this was early/preproduction batch that Triosmartcal received)ISO is total bull****. I'm facing that daily... (dealing quite alot with quality management iny my company) Even companies that are considered "quality" "brand name", having all the certificates ISO, TUV, OMG, WTF and probably even pope's blessing in written form often make such bad screwups that you would never think it's possible. And the field actually doesn't matter... semiconductor, passives, inductives, mechanical parts, chemistry, metal cast parts, nearly everything.

author: hans
author_rank: Super Contributor
timestamp: July 19, 2012, 12:30:06 pm
content: Going further offtopic about ISO...At my graduation place we had ISO9001 stuff too. All footprints, symbols , datasheets, etc. should be 'released' (thus verified) and organized on the servers. So we don't update datasheets, we like to work with outdated ones (the documentation for 'updating' an datasheet is horrible).Even more funny was that yes we release stuff, but the idea of releasing verified and examined material was never performed. If I looked in the workshop with past prototypes, lots of bodges and most of them were incorrect footprints or symbols. Classic mistakes. On my boards too, despite everything was verified and checked (as I was to believe). The ISO didn't help in that at all, it only gave extra paperwork and signing to do..I hate it too. It can be useful, but then all procedures should be thought off clearly and also followed. ISO was required there because they wanted to manufacture high-tech and medical equipment, where it apparently is required or boosts sales ('confidence factor'), which I understandEdit:@GK; that's how it works. You know how ISO certification went at grad company? One guy looks at your procedures, your product(s) and other crap. To reduce 'audit' time, they decided it was a great idea to drive 70km to a restaurant in Amsterdam, spent 1.5 hours dinner there, and drive 70km back again. "There were no issues"Total lunch time: ~4 hours. Total audit time: ~2 hours. Now the day is 'over' (6 hours mate? Where do I sign?) and he left.

author: tom66
author_rank: Super Contributor
timestamp: July 19, 2012, 01:03:29 pm
content: Very bad failure mode. It should fail with a fuse blown or 0V output. If they had a ~36V TVS on the output the worst case would be a blown fuse. But no... There's a reason I prefer an old surplus PSU to a new crappy one...

author: T4P
author_rank: Super Contributor
timestamp: July 19, 2012, 01:33:00 pm
content: Quote from: tom66 on July 19, 2012, 01:03:29 pmhttp://the4thpin.comeze.com/2012/07/06/lodestar-8202-teardown-purchase-location-reveal/I think you'll like this one ... it's from the 80's and in top order(PS: Full power is actually 4.5Amps per channel at 30V ... )

author: madires
author_rank: Super Contributor
timestamp: July 19, 2012, 01:33:45 pm
content: Hi!Quote from: EEVblog on July 19, 2012, 09:01:24 amI'm reading: We messed up that batch, but didn't tell anyone and let the resellers sell the bad units. Bad luck for you if you got one of those. We fixed the problem and you may buy a new one (and help us making more money).Cheersmadires

author: Scopeman1
author_rank: Contributor
timestamp: July 19, 2012, 01:37:31 pm
content: Can we stick to topic? ISO is polluting this thread. There are exceptions to all rules and we all know situations when quality systems get in the way of a good product, right? We designers are probably the most non-conforming and hopefully creative people on the planet, so of course we hate ISO or anything else that forces conformity. It is for the boring people in the QA dept so that hopefully someone ends up with what we intended over and over again. If a company chooses to have a quality policy and have it audited then good for them. Any company's quality policy, ISO or not, is only as good as its processes, implementation and its mangers making sure it is followed. If your hot new product is depicted in a folder full of scribbles then whose fault is that? And in 5 years when it needs repair and the folder's gone missing, same thing. So long as having a QA policy is not used for inflating prices then you are probably safer buying from a company that has an ISO9000 quality system than buying from one that has not. There will be of course exceptions. So start a new thread for more ranting on ISO9000 and let's see how this PSU situation develops. It sounds like they developed a 3A supply then pushed it to 5A with nothing more than a bigger transformer and it crapped out.Hmmm I suppose this post was mostly a bit off topic too.... must be a breakdown in the blog's QA system....

author: Scopeman1
author_rank: Contributor
timestamp: July 19, 2012, 01:50:14 pm
content: To add to madires' comment. If it was not for TRIO Smartcal's QA policy, they would still be selling it. How many other Korad resellers round the world have seen this and have also taken it off sale until they know they have good ones? Plus Dave can we have a comment from Trio Smartcal about what they will do about those they have sold already?

author: free_electron
author_rank: Super Contributor
timestamp: July 19, 2012, 02:46:33 pm
content: Quote from: EEVblog on July 19, 2012, 09:01:24 am-gasp- surely a top quality brand like Korad would not have bought a lot of transistors from some shady chinese parts broker that sanded off the real manufacturer and put some other, more expensive part number on them?As for ISO : there is nothing wrong with that. It is just a standard for traceability and process. But, and this is the key point : it does not define the actual process.. It only ensures you can track things. Yes it is a quality standard, one that measures the quality of the papertrail. I also prefer to but stuff from iso companies. You wont find any shady fake parts dealers there. And if you do, you will be able to track where the stuff came from and get your money back.Now, as far as the hammering on calibration companies goes : i am not going to blast triocal here, i got no quarrel with them and do not know how they operate, but : i would assume that they would have tested these supplies under max volt, max load for 24 hours. Meaning: set the supply at 30 volts and pull 5 amps from it. Leave foer 24 hours. If no magic smoke escapes. Pass.Since korad doesnt specify anything else like impulse behavior or load regulation.. Can't really verify..In general ( again: i do not know triocal and have no quarrel with them ) , it is my experience that calibration companies only verify that a product falls within manufacturers specs. If korad only gives two numbers there is little to verify. If the manual lists a thousand numbers under different test conditions they will have a lot more work. So if this korad thing, with the meagre manual fries under some weird condition you can't blame triocal. There were no specs. Like dave said : safe operating area ? Unknown. It may very well be that you can only draw 5 ampere at 30 volt. Dial it down to just above the relay switchover and the thing may go outside of the soa as that is the point where the transistors burns off the most heat. Its got full voltage from transformer and lowest at output , not causing switching down of transformer. And then smoke comes out.... If this is not documented... Point finger at manu for not documenting this. The manu may be ISO, but if its not in there its not in there. There is a paper with specs, check , ISO stamp...Second point. Most callabs ( i'm not fingering triocal, i dont know them. This is again just my experience) do not have the skill or know how to adjust a machine and bring it back into spec. It's pass or fail. Or they send it to the manufacturer for alignment. There is a lot of small callabs that do cal a multimeter for 50$ they also do a scope for 100$.... Really ?Third point : some callabs jave no clue what they are doing. We got two power supplies rejected because they outputted -0.3 volt at 60 mA when the output was 'off'. I contested that and told them to read service note xyz of the manufacturer. For a particular range of serial numbers this was normal. This note was an addednum to the specs. Their answer was ' we can't know everything... I kicked them out. As a callab it is your job to know those things. How can you perform a verification if you don't know what you are verifying....Fourth point: it is your job as user to read the manual of the machine you are using and know its limitations and specifications. Of course, if none are given your guess is as good as mine. Serious manufacturers will have calibration intervals given in the manual and the verification / adjustment procedures will be available, free / paying / or there will be a procedure to return it to the manu for calibration. If there is no procedure ,( either as a document , paying or free, or a statement it must be returned to manu ), ... Run for the hills....

author: jpelczar
author_rank: Contributor
timestamp: July 19, 2012, 03:07:29 pm
content: I guess one of the Murphy laws kicked in. Even if you think you test everything 100%, you'll find a bug/glitch one day after the product is in the shop ...Quote from: GK on July 19, 2012, 12:59:06 pmI think small "incentive" in the envelope was involved there ;-)

author: tom66
author_rank: Super Contributor
timestamp: July 19, 2012, 03:17:45 pm
content: I have a nice 30V 3A power supply by Tagasaki, quite old, not sure how old though, made in Japan.Built like a brick and weighs as much as 100!

author: Bored@Work
author_rank: Super Contributor
timestamp: July 19, 2012, 07:12:00 pm
content: Quote from: Scopeman1 on July 19, 2012, 01:50:14 pmIt doesn't take a policy to make a business decision. And it doesn't require ISO. All it takes is the boss saying "We stop selling this for the moment".

author: Unknown
author_rank: Unknown
timestamp: July 19, 2012, 11:57:46 pm
content: Quote from: Scopeman1 on July 19, 2012, 01:50:14 pmNot really. QA policy would simply require you to document who you were selling the suspect batches too and when you did so. Trio withdrew the product from sale based on Dave's experience. That is an action to protect both themselves and potential customers.All this second guessing and speculation about extensive test procedures that could have been, is fanciful stuff, devoid of commercial reality. You cannot economically or practically test for EVERY possible eventuality and you certainly cannot repeat that level of testing for every batch.The problem with QA certification is in it's implementation. Pedantic regulation that has all too often replaced common sense practices with inappropriate compliance practices. The real tragedy is a national emphasis on QA with little or no recognition of the value of QC or common sense. Bow ties and bullshit at 30 paces, and a regulatory environment that impedes rather than assists industry.From my point of view I'm glad that vendors like Trio Smartcal are prepared to put stuff forward for tear-downs and evaluation. I am also heartened that action was taken based upon the results. There is no basis for universal condemnation of this or any product based upon a single review or incident. Sure you can find bulletproof gear but good luck finding it in the price bracket where the Korad exists. What we have seen is a vendor who acted quickly and some response from a manufacturer. Compare that with your mileage buying a similarly priced item off eBay from vendors you know little about. If the fault takes anything more than a fortnight to emerge you'll essentially be on your own.Alternatively you could pay up to twice the price for a similar item from national parts chains. Why? Because they factor a proportional rate of failures, hand you a replacement and jettison the original in the nearest skip bin. Failure rate becomes too high they withdraw the line without notice. Good luck seeking long term support.At it's price point I'd still consider a Korad from another batch, Dave's experience giving me a heads up on some possible failures. For a critical application I wouldn't have been considering something in this price bracket in the first place.

author: george graves
author_rank: Super Contributor
timestamp: July 20, 2012, 12:11:26 am
content: SO I'm confused. Was Dave's unit a pre-production model that has since been fixed? Or is there a flaw in all of the units on the market?Call me crazy but I'm still considering buy one, if I can just confirm that the issue has been fixed or not.

author: cknight
author_rank: Newbie
timestamp: July 20, 2012, 12:14:52 am
content: I'm kind of curious about the apparently undocumented over-voltage and over-current buttons. What do these buttons do exactly? Are they enabling/disabling OCP and OVP? And if so, what state were they in when the unit failed?It's also curious that sight unseen Korad is attributing it to a transistor. It would seem to me that they must have been able to duplicate the failure or they already knew that the transistor is under-rated already.Cheers,~Chris

author: ivan747
author_rank: Super Contributor
timestamp: July 20, 2012, 12:38:41 am
content: Quote from: george graves on July 20, 2012, 12:11:26 amFair call. If you decide to buy one, remember to make a video!

author: EEVblog
author_rank: Unknown
timestamp: July 20, 2012, 04:19:20 am
content: Quote from: george graves on July 20, 2012, 12:11:26 amI think it was "early production", not pre-production. There is the real possibility some other suppliers may have got dud units too.QuoteKorad claim it is fixed and no one else will have the problem.I believe them for future shipments, but I suspect that's not guaranteed for any previous shipments.Dave.

author: EEVblog
author_rank: Unknown
timestamp: July 20, 2012, 04:23:39 am
content: Quote from: cknight on July 20, 2012, 12:14:52 amI believe you can see in the video that they were switched off.Whether or not that means the unit is no longer protected from shorts or whatever, I have no idea, as we are not told how these modes work at all, or what the performance envelope the unit is actually designed for.QuoteI get the sneaking suspicion that they may have already knew. But I could be wrong, they may have just investigated very quickly and it was an immediate "Doh!" moment. Like shipping the 3A board in the 5A unit or something like that?Dave.

author: george graves
author_rank: Super Contributor
timestamp: July 20, 2012, 04:44:10 am
content: Quote from: EEVblog on July 20, 2012, 04:19:20 amHmmmm. I wish there was someway to know before ordering (say from ebay or amazon, other than your supplier) if the problem has been corrected on those units.And the problem is fixed, but it's still pulled off their site? (scratches head)

author: Bored@Work
author_rank: Super Contributor
timestamp: July 20, 2012, 05:19:10 am
content: Quote from: george graves on July 20, 2012, 04:44:10 amI would not take Korad's statement too serious. For me it is a case of that they told people what they would like to hear, not what really happened. Something very typical in China. I would not be surprised if Korad didn't change anything in the past and has no intention of changing something in the future. The heatsink/fan combination on that thing is is so bodged, it might kill any transistor, bad batch or not.But if they knew about it, if they still shipped the units, or not telling their retailers once they learned about it, you can extrapolate what their behavior will be next time there is an issue. A voluntary recall it won't be.And the point with Trio Smartcal is, they opened it, they followed their process, but no one there said "uhm, that is not good enough". They wanted that thing. And if you start your evaluation from the point of view "we want it", or if your process is biased that way ("how can we accept things?", instead of "how can we protect ourself from junk?"), you end up taking such things on board. The reality is that maybe that these days no one, not even the Chinese can't make an acceptable $99 programmable PSU.

author: george graves
author_rank: Super Contributor
timestamp: July 20, 2012, 05:41:21 am
content: Here's the manual BTW:http://sra-solder.com/shopimages/products/instructions/KA%20user%20manual%28single%29.pdf

author: T4P
author_rank: Super Contributor
timestamp: July 20, 2012, 07:18:55 am
content: BAW... HK people have different mindsets than people from china

author: ejeffrey
author_rank: Super Contributor
timestamp: July 20, 2012, 01:53:20 pm
content: Quote from: cknight on July 20, 2012, 12:14:52 amProbably the OCP and OVP are done in software. That is, when the MCU detects an OV or OC condition, it turns off the output by setting the output to zero. Since there is no separate turn-off relay or even a FET, once the main pass transistors blew out, they performed no function.

author: TestBox
author_rank: Contributor
timestamp: July 20, 2012, 02:38:29 pm
content: If someone who is simply bored at work and has nothing better to do than conjure up speculative crap about what the Chinese thought, did, will do etc when they don't have a shred of evidence to support their allegations, and would simply wait with the rest of us, then we'll get a true picture of what's going to happen here. Dave has a blown up unit. If a new board turns up with different transistors then we'll know the truth. If it has the same transistors then we can draw our own conclusions. In the meantime Trio SmartCal has done the right thing by taking them off the market until it's sorted. That seems reasonable to me.

author: Bored@Work
author_rank: Super Contributor
timestamp: July 20, 2012, 02:54:36 pm
content: Quote from: TestBox on July 20, 2012, 02:38:29 pmYou work for Trio, don't you? But anyhow, feel free to kiss my arse any time it is convenient for you.Oh, and I deal regularly with Chinese companies and engineers. Bunch of liars, all of them.

author: T4P
author_rank: Super Contributor
timestamp: July 20, 2012, 06:53:39 pm
content: Yup, mostly liars. BAW's right there.No matter which nation, china or hongkong ( even koreans! Those d!cks! )they lie.

author: Unknown
author_rank: Unknown
timestamp: July 21, 2012, 12:06:46 am
content: Quote from: Bored@Work on July 20, 2012, 02:54:36 pmWhat part of that engineering degree did they devote to coming up with wild conclusions?QuoteWhile I'm not one to deny anyone from acting out their particular fetish. You do need to realise that 1) this should always be done a sufficient distance from livestock and 2) it is likely to result in your ending up with lipstick stains on the back of your head.QuoteI deal daily with Europeans, Yanks, Canadians, Asians, pasty Poms and fellow Aussies . As a competent engineer the only reasonable conclusion I can draw is that any generalisation s based upon races would range from flawed to plain ignorant. Was "racial stereotyping" included in that old school tie education of yours before or after they did "Wild Conclusions"?

author: TestBox
author_rank: Contributor
timestamp: July 21, 2012, 02:27:36 am
content: Given Bored's rear-end fetish, we might have to check the dictionary for all meanings of "bored" to make sure we have the right one for why he really is "bored"@ work. That then begs the question does he enjoy his job?

author: PbFoot
author_rank: Contributor
timestamp: July 21, 2012, 02:28:01 am
content: A friend of mine bought a cousin of the Korad unit - its a Quakko HY3005DP. Along with the infamous full output power for 1 second on power on, it has some other serious problems. I've taken apart the unit, and it does have significantly different construction internally when compared to the Korad.He cooked his PS in almost the exact same conditions, and it exhibited almost exactly the same failure mode. ETA: (As the Korad did in Dave's video.)I am sad to say I also have one of these HY3005DP, and it's a total pile of crap. I don't run it at high loads, so it still works, but next time I am getting an entry level Agilent.-PbFoot

author: Unknown
author_rank: Unknown
timestamp: July 21, 2012, 03:10:31 am
content: Quote from: PbFoot on July 21, 2012, 02:28:01 amWe have seen this with lots of budget test equipment, the cases are sourced and/or cloned by a number of suppliers and assembled for different markets and budget extremes.While units may look like a simple re-badge they be entirely different in construction and performance. It's another reason why you are always better to source budget stuff from known supply sources.

author: Ed.Kloonk
author_rank: Super Contributor
timestamp: July 21, 2012, 04:48:14 am
content: Quote from: grenert on July 19, 2012, 02:58:56 amI fully agree. I own a 20 year old Altronics 50v (3-35v/5a) switchmode psu kit. It has two analogue meters on it that are connected right to it's output. Nice multiturn adj pot. No current limiting but it is sure nice to be able to glance over and see what's going down the wires.The other remark I wanted to make is about the serial and usb connectors on the back of the power supply. On the back? Wouldn't you prefer then on the front panel?I noticed that the input rating says 220v. I knew an electrician who had a fight with and air conditioner company whose machine was rated 220v and then claimed that it was not covered under warranty because it had been wired to Australian 240 volts.I wonder if that is what happened to the psu. I saw that the tranny is rated 240, but you know the circuity in these cut-price gadgets isn't designed with a whole lot of plus/minus in mind.hmmm. The thot plickens.

author: EEVblog
author_rank: Unknown
timestamp: July 21, 2012, 05:55:50 am
content: Quote from: Ed.Kloonk on July 21, 2012, 04:48:14 amAustralia is not officially 240V any more. It's 230Vhttp://en.wikipedia.org/wiki/Mains_electricity_by_countryDave.

author: Ed.Kloonk
author_rank: Super Contributor
timestamp: July 21, 2012, 06:00:21 am
content: Quote from: EEVblog on July 21, 2012, 05:55:50 amBastards. They just stole ten volts from me.Give it back!

author: SeanB
author_rank: Super Contributor
timestamp: July 21, 2012, 06:16:46 am
content: Ed, a lot of compressors are wound for 200V, as this saves copper in manufacture. Of course it will overheat........ But again most are connected with undersize cabling anyway, so it evens out, warmer wire and cooler windings. Note that they are still marked 220v in this case.

author: IanB
author_rank: Super Contributor
timestamp: July 21, 2012, 06:22:11 am
content: Quote from: EEVblog on July 21, 2012, 05:55:50 amYou should definitely measure the actual voltage at your mains sockets and see what the meter says. My guess is that if the system was originally designed for 240 V then it is still 240 V. It is a huge cost to change installed infrastructure to a different specification. It is much cheaper to change the voltage on paper by adjusting the allowable tolerance.

author: David_AVD
author_rank: Super Contributor
timestamp: July 21, 2012, 06:38:51 am
content: Yes, when we changed to the 230V standard it was only on paper. Just the tolerance was changed. I still measure 240V - 245V at the socket.

author: HackedFridgeMagnet
author_rank: Super Contributor
timestamp: July 21, 2012, 07:02:03 am
content: One point I'd like to make is that Trio Smartcal's ISO:9 whatever accreditation didn't prevent them from selling what seems to be a bit of dodgy junk, one that fails and could possibly damage whatever it is attached to.I don't know how this PSU could come under the banner of quality assured. Not when the manufacturers details are sanded off half the chips.I don't suppose Trio Smartcal is going to publish the relevant parts of their QA manual. So we can be sure they followed it when they decided to put this PSU in their range.If Trio Smartcal were interested in assuring quality, they should put into their QA manual, "Dont sell equipment that contains chips that have their details sanded off."ps. I don't think Trio should actually do this, they should just skirt around the QA stuff like we all do.After all ISO QA accreditation is just a sales tool, one that lets you sell to Government and big companies, and helps keep small companies out.

author: TRIO_Smartcal
author_rank: Contributor
timestamp: July 21, 2012, 07:30:45 am
content: Things have certainly been getting interesting. More questions to answer and here's a bit of an update.1. What are doing about those we have sold?- We are already contacting the customers to advise them of the issue. They can have a full refund, or if the unit has survived Dave's treatment after modification, they can have their unit modified and returned. Korad has told us they are sending enough parts to modify all the remaining supplies we have in stock and those we have already sold.2. What if it fails after modification?- If it fails after whatever modification we need to do, then we will give customers their money back , or exchange for another brand at a preferential price on a case by case basis. We will then have a totally different discussion with Korad.3. The transformer Rating? - It is rated 240V. We had delivery delays because Korad only had 220V trannies when we first ordered. I suspect they didn't think of changing the sticker on the back.4. Connections for USB and RS232 on front or rear? I suspect if someone is hooking this up to a PC they don't want a serial or USB cable coming out the front as well as the supply leads and getting mixed up in the bench spaghetti. The USB is for PC connection not a memory stick so if it is rack-mounted or on a shelf above the bench, it is probably better on the rear panel. But that's a simple matter of personal preference ultimately.5. Someone else mentioned the ATTEN APS3003S-3D- This is a triple output supply and we sell truck loads of them. They sell for $249+gst off our website. Compare that to what you get from the big nationals. We offer it with a 2yr warranty. We have sold several hundred of them with with just one warranty claim. It is a good supply for the money. And it's a linear. And heavy!http://triosmartcal.com.au/dc-bench-supplies/2432-atten-aps3003s-3d-dual-power-supply-0-30v-3a.html6. Uncle Vernon is very correct in pointing out this forum is not a place for racial stereo-typing. We also deal with multiple suppliers from USA, Europe and Asia and we have had no real problems so far. Dealing directly with manufacturers is OK. They are looking for a long term relationships so you help grow their business and in my experience all those we have dealt with have been fine. It also comes down in the longer term to dealing with companies that you trust and the proof is when something goes wrong, as it has here. Trust is something that builds with experience and Korad is a new supplier for us, so we need to see how things develop.So far Korad has been responsive, Dave is copied on emails between us and Korad so he can back me up if he chooses.7. Whether Korad knew of the problem when they shipped to us is another issue, and if they found out later there was a batch issue, then leaving the problem for the distributor to find is not the best policy. Also it would depend when they found out be it last week, month, several months ago, I don't know the answer. But I do need to know. I have also asked for serial numbers of affected units.8. The sample we tried in our lab was from a different batch to the production units we have in stock. Dave does not have the sample we tested. That is in my garage, works fine, I use it for a quick charge on my boat battery and it comes in very handy. Dave tested an early production unit, hence my concern and the immediate withdrawal of the product from sale.9. Why did we take it on in the first place?Their products looked good on paper offering a good performance at a very reasonable price and down into the education market level and hobbist level. These PSU's filled a hole in our portfolio for a low-costprogrammablesupply and as one we tested met it specs we gave it a go. As I mentioned in an earlier post I have no problem submitting anything we sell for Dave to evaluate. If Dave finds something we don't then that's good for everyone. How this Korad situation now develops remains to be seen. I will certainly keep this thread posted with developments. We are just as intrigued as you are!! Korad's true business ethic and customer care will certainly come out now. If they do not rectify the situation then they are gone from our range and we take back those we have sold offering the remedies above. It's that simple.10. Someone else mentioned that the next supply they buy will be a low cost Agilent. Well I'll declare my bias as Agilent's biggest distributor in Aussieland and say that I totally agree. We sell Agilent bench supplies at less than Agilent's list price. That means they start price from us at just $336 +gst. See here :http://triosmartcal.com.au/1571-agilent-u8001a-dc-power-supply-30v-3a.htmlFor those in the market for one now, Agilent has an great offer on the E36xx series of bench supplies. If you buy a qualifying power supply from their E36xxA range for upwards of about $530 +gst they (we) will give you a U1272A multimeter for free. The meter sells for about $440 including gst.http://triosmartcal.com.au/2251-agilent-u1272a-dmm-digit-water-dust-resist.htmlClick on the banner here to see the offer.www.triosmartcal.com.au11. If anyone has further questions about this Korad situation and you can't wait for a post to be answered, then why not just drop me a PM. It goes straight through to my in-box at work. If I have the answer then I'll let you know, and if relevant to the others following this thread then I'll post it, otherwise if I don't know I'll try to find out.12. Just measured the voltage from the mains here in Castle Hill. It was 244.1V13. We don't check for chips with the lettering removed. I think this is were a grasp of reality helps. Why would you check for chip lettering on a $199 supply? To troubleshoot to component level is just not worth it. Companies remove lettering to protect their IP and big multi-nationals are doing exactly the same. Sure it pisses off geeks who want to know what the chip is, but is that why you buy something? Because the writing is still on the chips? Most don't.14. HackedFridgeMagnet thinks that ISO:9xxx could have stopped this getting into our range. Absolutely not. Look at Dave's first reaction to the product. Even during the tear-down. It came out OK for a $199 supply. In fact the review was going well until it failed. Now that it has failed when it shouldn't have failed is when QA really kicks in, and remember as someone else said, wrapping your head in tin-foil and singing Hare-Khrishna could be in your QA process but it has to be relevant. What has happened here since the failure is relevant the failure was recorded and appropriate action taken. No tin-foil harmed in the process. As for this comment QUOTE"ps. I don't think Trio should actually do this, they should just skirt around the QA stuff like we all do."........... You must work for one of our competitors ;-)15. Finally for David_AVD who did a very relevant post in the ShoutBox QUOTE: "Some People want the cheapest price and the best service / warranty. It doesn't usually work that way" END QUOTE. Well that's the challenge we all face as sales and service companies. We want to do just that to have a competitive edge. Again as stated earlier it comes down to you getting what you pay for so long as you are not being ripped-off which includes after-sales support & service.. It is all a balancing act that we have to perform with the variables in the value equation.Cheers & keep it coming.

author: Ed.Kloonk
author_rank: Super Contributor
timestamp: July 21, 2012, 07:47:12 am
content: @TRIO_SmartcalI commend you for having the balls to do what you are doing and for being bold to hand the gadget to Dave, the hardest, most critical in the biz. Good on you.Don't let them there knockers knock you!

author: David_AVD
author_rank: Super Contributor
timestamp: July 21, 2012, 07:50:20 am
content: Nice reply. TRIO Smartcal seem to be doing exactly what I'd expect any decent company to do.Local support and warranty is often undervalued. I buy some (usually very low cost) items direct from overseas and when I do, I accept that I am taking a calculated risk in doing so. (in regard to warranty, represented specs or even receiving the item!)I must admit my fist reaction was to give the Korad unit a miss after Dave's unit went belly up. Now I'm quite prepared to consider it if the issues are sorted and TRIO Smartcal offer it for sale. I'm damn glad I didn't jump in for the slightly cheaper option of buying in from USA and having no support.As for the sanded chips, I accept that's what some manufacturers do. It only annoys me slightly as a failure of that part would usually mean I'd just buy another unit anyway.It has to be remembered that this is a low cost power supply. Much cheaper than any of the other programmable units I've seen. The way some people are going on you'd think it was a very expensive high end product! It's all horses for courses folks.

author: SeanB
author_rank: Super Contributor
timestamp: July 21, 2012, 07:53:38 am
content: Add to this there are a lot of residential areas where there are feed in solar supplies where the mains voltage during the day is 260V or more, as the voltage compensation from the supplier is not meant to work the other way and get power fed from the load side.

author: Ed.Kloonk
author_rank: Super Contributor
timestamp: July 21, 2012, 07:54:20 am
content: Quote from: David_AVD on July 21, 2012, 07:50:20 amThis is why I don't understand why Gerry Harvey got nailed when he went after Ebay. He for some reason forget to ram home the point about local service that we all enjoy but sure miss when we bypass it.

author: Unknown
author_rank: Unknown
timestamp: July 21, 2012, 08:08:43 am
content: Quote from: Ed.Kloonk on July 21, 2012, 07:54:20 amPerhaps because of HN and other discount appliers (generally illegal) attitude towards warranty and customer support. Once that card is swiped they don't want to know you. The expectation being you should seek out the manufacturers service company. The established retailers just don't get it. Which is why they are losing out to online retailers. Often times you can be better looked after by an online vendor.The vendors that support their products, who provide price and specifications online and those who are prepared to interact with new media are the ones who will benefit and grow.

author: HackedFridgeMagnet
author_rank: Super Contributor
timestamp: July 21, 2012, 08:22:11 am
content: QuotePs. I am a reluctant calibration customer, not a competitor.Just so people are clear, I am not knocking Trio Smartcal or the the way you are handling this situation. I have to say you are going to lengths that I can't remember any distributor ever going. Well done, may it continue.I am also not knocking you for selling inexpensive stuff rather than just the name brands. Sometimes it's every bit as good.But I am knocking the QA accreditation system and the way sales people use it to imply that Quality is Assured when it is clearly not, because you don't know who made the chips, when they were made or even what they are. Do you even know if they are Pb free. If so how?And I would be interested to know what your QA manual does say about how you check equipment before you sell it. Though I guess you will have to 'skirt around' answering this one. I can understand though.

author: amyk
author_rank: Super Contributor
timestamp: July 21, 2012, 11:46:15 am
content: After rewatching the review it looks like more than just the power transistors failed; why would it switch to the 56V tap when the preset voltage was far lower? I'd think that a good control loop would notice the abnormally high output voltage and go to the lowest tap, then maybe even detect that the voltage is still too high and shut off completely at the relays.56V also looks a bit high for a supply that's rated for only 30V.

author: madires
author_rank: Super Contributor
timestamp: July 21, 2012, 12:48:38 pm
content: Quote from: PbFoot on July 21, 2012, 02:28:01 amPlease readhttp://blog.mastechpowersupplies.com/(top entry)The special feature for pre-setting the current limit is absolutely gorgeous :-)))Cheers

author: T4P
author_rank: Super Contributor
timestamp: July 21, 2012, 06:22:00 pm
content: Quote from: amyk on July 21, 2012, 11:46:15 amMaybe the relays failed and switched in all 3 taps? All did the transistors go short and recieved all 3 tapsIt does sound like there's 15-15-0-15-15 to meDave, how many taps are there on the PSU?

author: amspire
author_rank: Super Contributor
timestamp: July 22, 2012, 01:31:14 am
content: Quote from: HackedFridgeMagnet on July 21, 2012, 08:22:11 amIt is not up to QA to second guess the designers.It is up to QA to act when an issue of quality arises, which Trio Smartcal have done pretty brilliantly.It is not just the cheap Chinese products that have batch problems. I own a bunch of HP 49G calculators thanks to a major batch problem that HP had. They had a batch of leaky capacitors that they used to back up memory as you change the batteries, and the result was the calculators wouldn't turn on. Change the capacitor and they work perfectly. To my knowledge, this problem affected just about every calculator using this batch of capacitors.Are you suggesting that no-one should sell HP calculators?Batch component problems happen in manufacturing, and the important thing is the response of the manufacturers and suppliers to this problem. It can happen to any manufacturer using components from any supplier.It could be that this Korad supply has a design problem, and the correct response from QA is to to see that either the problem is fixed, or to recommend the product be dropped.Do you have any problem in the way Trio Smartcal have responded?I have never heard of any QA department of a distributor requiring that a third party manufacturer detail the source and date of manufacturing of every component in a piece of equipment that they make.Richard.

author: jeremy
author_rank: Super Contributor
timestamp: July 22, 2012, 07:47:03 am
content: Just putting it out there, but I want one. Two actually. Looks like a nice unit for small automation tasks. Hoping to hear from the guys at trio soon.PS: stuff goes wrong guys. No-one is immune, not even NASA:http://articles.cnn.com/1999-09-30/tech/9909_30_mars.metric.02_1_climate-orbiter-spacecraft-team-metric-system?_s=PM:TECHIf Korad (and by extension, Trio) are going to fix it, then I'm happy. You'd get the exact same treatment if your 9000 series Agilent scope popped.

author: HackedFridgeMagnet
author_rank: Super Contributor
timestamp: July 22, 2012, 12:04:58 pm
content: QuoteI was under the impression that Quality Assurance is about preventing these issues arising.If they do arise then it is about preventing them from arising again.These are lofty goals, and I subscribe to them, but my experience of ISO:9000etc is that it doesn't necessarily assure anything except a lot of ticked boxes.

author: Unknown
author_rank: Unknown
timestamp: July 22, 2012, 12:12:47 pm
content: Quote from: HackedFridgeMagnet on July 22, 2012, 12:04:58 pmNo it's about tracking and managing process so action can be taken when events arise. The word Quality should never appear in the title.Sadly however more often than not QA is used as a blunt instrument to restrict or price out emerging competitor. It is also a tool for government authorities, insurance companies and large corporations to duck-shove blame and avoid accountability.The we have lots of folders full of stuff so it can't possibly our error syndrome. Like throwing buckets of money, a short time- frame and some unrealistic expectations at an industry, while remaining three steps removed from the people who do the work. Then when all the roof batts catch fire and people start getting electrocuted you can blame fly by night contractors and obfuscate yourself from any responsibility. Worked for Kev, Pete & Julia.

author: amspire
author_rank: Super Contributor
timestamp: July 22, 2012, 12:17:11 pm
content: Quote from: HackedFridgeMagnet on July 22, 2012, 12:04:58 pmI do not think the QA department is meant to be capable of magic, or predicting the future.QuoteTrio Smartcal removed the supply from their catalog until the problem is identified and sorted. Then they will probably decide whether to sell it again or not. It sounds to me like they have done everything possible to prevent the problem happening againQuoteISO9001 is just a standard that makes you define the quality assurance procedures in your company, and ensures you follow your own procedures. You tick boxes if the QA procedures that you defined require you to tick boxes. If you have to tick boxes, you cannot blame ISO9001.When you are assessed to see if you meet the 9001 standard, they check that your company is following the QA manual that you wrote for the company.The procedures are as good or as bad as you make them. When a company like Trio Smartcal advertise that they are 9001 qualified, it indicates the company has written QA procedures, and that customers can expect the procedures are followed. This is important for customers like government departments.Richard.

author: HackedFridgeMagnet
author_rank: Super Contributor
timestamp: July 22, 2012, 12:59:26 pm
content: QuoteWell now I am confused,They have written procedures, apparently about QA but possibly not about the quality or the testing of the equipment they sell.The procedures are about how they react if an issue of quality comes up.I am supposed to trust them to carry out these procedures because they are accredited. Fair enough, but still they write these procedures themselves so I don't know what they are unless they tell me.I don't feel much safer.Sorry for being disingenuous Richard, but I feel you are too.QuoteTesting equipment before selling it is quite common.Documenting these test procedures is also quite common.Using these tests to estimate failure is quite common.The fact that these tests are apparently not part of Quality Assurance is news to me, but I am not QA expert.I did not mention magic.I think you missed this part of one of my posts Richard.Quote

author: taemun
author_rank: Regular Contributor
timestamp: July 22, 2012, 01:50:42 pm
content: Quote from: Denno on July 18, 2012, 11:12:50 pmI think this was mostly overlooked, and (to my mind) is the correct interpretation of *that* 'fault'. Constant wattage is pretty much useless for switch on testing.I groaned when I saw the teardown, the overall internal build was very reminiscent of myJaycar MP3087. That unit has no fan, and badly needs one when powering a high current load - a 100W LED will make the output transistors untenably hot in a relatively short period. Also, its regulation was so poor that you could visibly see the current (in CC; or voltage in CV) ripple in the LED's light output.[Edit: in particular, I noticed the chassis had the same dodgy roof rails which didn't meet the front panel at a right angle.]On the other hand, I can't say enough good things about Agilent 6632B's. A few of them fell into my lap a year ago. They can source or sink 20V/5A (yes, it'll sink full rated power). Sinking is incredibly useful, as is the 20mA (1uA resolution) current sense mode, when dealing with small project power supplies. Testing switch-mode PSU efficiency couldn't be easier.The 6632B fan is noticeable, and entirely current load based, but these are really designed for rack-mount use, and I doubt that most folks care how much noise their equipment rack makes - it means the units stay cooler and hence last longer.Considering that you can buy that Korad for $US 75 on AliExpress (plus postage), I wouldn't expect anything good to come from them. Sticking "Lab Grade" on a product doesn't make it so.

author: nixxon
author_rank: Frequent Contributor
timestamp: July 22, 2012, 03:53:23 pm
content: "Considering that you can buy that Korad for $US 75 on AliExpress (plus postage), I wouldn't expect anything good to come from them. Sticking "Lab Grade" on a product doesn't make it so."I have only seen the D and not the P(rogrammable) version at AliExpress...nixxon @ iPhone in Ste.Maxime, France at the moment...

author: amspire
author_rank: Super Contributor
timestamp: July 22, 2012, 04:26:27 pm
content: Quote from: HackedFridgeMagnet on July 22, 2012, 12:59:26 pmThey did test the supply before offering it for sale, and their test supply worked. How can you estimate failure when the supply does not fail in tests? It is a very cheap programmable supply, so they would not expect it to be a top quality design and build.The unit Dave got was from a different batch, and it was working for most of Dave's review. It was not faulty initially. It failed while Dave was testing.QuoteIf you are not knocking Trio Smartcal's QA, what on earth have you been whinging about?Even for the manufacturer, QA and QC (quality control) are two completely different things, and I think you think they are the same. Do you understand that a company with the highest QA standards can choose to sell a cheap low quality product without any conflict of the QA standards?Lets get back to basics.One power supply has failed. The supplier has taken appropriate action. A big tick for the supplier. It appears the manufacturer has been communicating with the supplier and seems to be taking appropriate action. So so far, a tick for the manufacturer.Failures exactly like this can happen with any company and with products of any price.Let's acknowledge everyone who has done the right thing, let's see what happens, and just move on. There are people in this forum wanting to see if the manufacturer can resolve the problems, as they see the supply as something very useful at the price, even if it is a cheaper construction, and even if the boards are not cleaned as well as they could be.Richard.

author: george graves
author_rank: Super Contributor
timestamp: July 23, 2012, 12:23:59 am
content: I think I'm going to go ahead and buy one. It seems you can get one in the US for $100 shipped - with a 2 year warranty. Even if it lasts 2 years and 1 day, then blows up, that's still a heck of a deal, and should suit me just fine. There is very few times I need more than 1 amp - so in my case, it should see very light use.I'm just so impressed with the accuracy of the displays, and the controls. It seems like a +$300 PS for $100.There were a few people stating "well, see, you can't make a decent programmable PS for $100! - Told ya!" - well, why not? It's a transformer, a case, some LED's and a hand full of other parts. I don't see why not.I'd like to buy something that is a bit more "industry standard" - but in a pinch, this will do nicely. And in two years, I'm sure I'll have added a lot more equipment to my lab.My 2 cents.

author: HackedFridgeMagnet
author_rank: Super Contributor
timestamp: July 23, 2012, 04:25:45 am
content: I did a quick search on QA vs QC and this was the first site found. They even have a picture.http://www.iso9001consultant.com.au/QA.htmlQuoteI dont know if it's right or wrong but it is not consistent with what you say.QuoteThe nub of what I have been trying to say is that a company having QA accreditation doesn't assure me personally of anything.The psu failing only reinforced this view.Whereas the brand name Trio Smartcal does give me reason to feel assured, because I have heard of them, have dealt with them and know of others that do the same.

author: taemun
author_rank: Regular Contributor
timestamp: July 23, 2012, 07:14:59 am
content: Quote from: nixxon on July 22, 2012, 03:53:23 pmApologies, I didn't notice the D suffix as opposed with the P suffix. My point still stands though, that isn't $100 worth of isolated USB/RS232 board.

author: amspire
author_rank: Super Contributor
timestamp: July 23, 2012, 07:36:32 am
content: Quote from: HackedFridgeMagnet on July 23, 2012, 04:25:45 amWhat that graph is not explaining is that QA is about defining and managing the processes in a company, not the quality of products. As QC is a subset of the processes in a company, it is under the QA, but the QA processes are only concerned that your QC is running in a proper way. A manager in the company defines how QC should operate, and then QA ensures that these rules are followed. QA is about defining comprehensive processes and rigorously following these processes, rather then making it up as you go along. So if a product fails, rather then a manager saying "What will I do now?", people look up the QA manual to see what steps have to be taken, and they follow the steps. QC is only shown as part of QA in the same way that every other process in the company will become part of QA.QuoteIt is consistant if you understand what I have been saying. QA means you are dealing with a company that will handle complaints in a standard manner. You are not at the mercy of the mood of the representative you are talking to. Dealing with company with good QA standards is a good thing, but not in the way that I think you want.I think you want a quality product.QA does not care less about the quality of a product unless the company has written rules defining a process to determine the quality of a product. Once there are rules, then ISO9001 QA requires that the rules are followed, and if they are not followed properly, a non-conformance reportmustbe raised within the company. This non-conformance report must then be acted on in some way - it cannot be ignored. If the independent ISO9001 inspectors see there are non-conformance reports that have not been addressed, they can suspend the company's ISO9001 accreditation.QuoteIt does not assure you that a product the company is selling is high quality. If they are selling a low quality product, you get a low quailty product, and that is totally fine with a good QA system.However, a good QA process is important when companies have to cooperate as it means that the QA processes of the 2 companies can be set up to work together efficiently. A big reason Trio Smartcal has ISO9001 is because many other potential clients, particularly governmental organisations, require they have ISO9001. These customers will not do business otherwise. That is why the ISO9001 compliance is advertised.Richard.

author: Galenbo
author_rank: Super Contributor
timestamp: July 23, 2012, 09:00:46 am
content: Quote from: amspire on July 23, 2012, 07:36:32 amAnd even, to produce absolute CRAP products, you need good machines and a good Quality control,when not, you'll not be able to produce CRAP in high volumes

author: HackedFridgeMagnet
author_rank: Super Contributor
timestamp: July 23, 2012, 09:49:58 am
content: I don't wont to think about Crap in high volumes, it's dinner time.You're probably right, RichardBut from personal experience, I see a red flag when people mention QA accreditation.I'll leave there.

author: MBY
author_rank: Regular Contributor
timestamp: July 25, 2012, 09:13:59 am
content: Quote from: amyk on July 21, 2012, 11:46:15 amExactly my thought! It's a bit confusing when we have two "contemporary" threads about the PSU. In the threadhttps://www.eevblog.com/forum/product-reviews-photos-and-discussion/korad-ka3005d-$90usd-30v-5a-dc-programmable-ps/ I was also rising the concern that it not make real sense to assert that the transistors where the only thing failing.As you said, the control loop should switch in the right taps for the right setpoint not matter the actual voltage. Maybe the control loop broke and put those transistors out of SOA. The transistor failing may be the effect, not the cause. It could be something as easy as a bad solder joint, especially if the schematics of the relays are dumb so non energized relays switch in the highest tap, not the lowest.Btw, I agree with Scopeman1 - lets keep the QA and ISO stuff outside the thread. The electronics is more exciting.

author: itdontgo
author_rank: Regular Contributor
timestamp: July 25, 2012, 12:40:50 pm
content: Quote from: Psi on July 18, 2012, 04:33:48 amThis can be useful when you play a melody through a piezo. If you use a PWM the perfect square ware sounds louder and quieter around resonance. The dirty software interupt driven output plays at a more constant volume!

author: itdontgo
author_rank: Regular Contributor
timestamp: July 25, 2012, 12:42:30 pm
content: Someone at Korad has been found out.

author: LEECH666
author_rank: Frequent Contributor
timestamp: July 27, 2012, 12:45:56 pm
content: *Sigh* Why don't they offer that Agilten 36xx PSU + Free Multimeter deal in Euroland? I really would considder buying, but shipping cost + custom taxes would really take the fun out of such a deal.

author: MickM
author_rank: Regular Contributor
timestamp: August 06, 2012, 02:00:48 am
content: Hi;is there any update on this?Was the problem found?Mick M

author: MBY
author_rank: Regular Contributor
timestamp: August 08, 2012, 07:45:20 am
content: I'm also looking for updates. Anybody has any news?

author: TestBox
author_rank: Contributor
timestamp: August 27, 2012, 01:54:47 pm
content: According to Trio Smartcal there is a delay at Korad's factory. I got the impression Trio Smartcal was not very happy with Korad. Neither would I be if something dragged on this long. Apparently the parts to rectify the problem were supposed to be shipped weeks ago but Trio is still waiting. Knowing the Chinese they'll be waiting a very long time. Glad I didn't buy one from overseas.

author: EEVblog
author_rank: Unknown
timestamp: August 27, 2012, 02:00:30 pm
content: Quote from: TestBox on August 27, 2012, 01:54:47 pmKorad have said they were moving office location which has caused the delays.Dave.

author: GEuser
author_rank: Frequent Contributor
timestamp: August 28, 2012, 05:14:37 am
content: Mr EEVblog , what is that bendy thing on the bench on the right in the video , a light?cheers , Paul .

author: T4P
author_rank: Super Contributor
timestamp: August 28, 2012, 07:13:44 am
content: Quote from: GEuser on August 28, 2012, 05:14:37 amHis brand new mantis elite microscope

author: Unknown
author_rank: Unknown
timestamp: August 28, 2012, 07:17:26 am
content: Quote from: GEuser on August 28, 2012, 05:14:37 amHis elbow?

author: GEuser
author_rank: Frequent Contributor
timestamp: August 28, 2012, 12:46:40 pm
content: Thanks very much T4P , great gizmo and "i love the smell of mantis in the mornings"@UV , LOLcheers....

author: ProBang
author_rank: Contributor
timestamp: October 28, 2012, 06:17:26 pm
content: HelloQuote from: EEVblog on August 27, 2012, 02:00:30 pmYeah, that's two month ago. IMO enough time to establish business as usual.Once more:I'm also looking for updates.Is there any update on this?Was the problem found?Anybody has any news?Greetings,Hartmut

author: EEVblog
author_rank: Unknown
timestamp: October 28, 2012, 09:40:50 pm
content: Quote from: ProBang on October 28, 2012, 06:17:26 pmCharles copies me on the email correspondence, which basically consists of him getting more miffed by the day they haven't responded, and Korad coming up with a new excuse each time. I think the latest excuse is that they haven't finished the Labview driver!I think both of us have given up all hope of ever getting the problem resolved. And Trio are left holding a bunch of these lemons in stock.Dave.

author: Unknown
author_rank: Unknown
timestamp: October 28, 2012, 10:22:02 pm
content: Quote from: EEVblog on October 28, 2012, 09:40:50 pmWhat Trio do have in stock, if your after a budget priced PSU, is the QJE PS-3005, it's no programmable, it's not the quietest electrically or audibly. Still at under $100, it remains a bargain and a good entry level alternative for those wishing for a basic 0-30V 5V supply.http://www.triosmartcal.com.au/dc-bench-supplies/2631-qje-ps3005-bench-power-supply-150w-0-30v-0-5a.html

author: ProBang
author_rank: Contributor
timestamp: October 29, 2012, 11:15:32 pm
content: Hello@ DaveVery disappointing, how this manufacturer take care about his customers.BTW:I've seen the Korad PSU in the background during some videoblogs.In the last blogs no more...Find the PSU the way, following a ballistic curve, straight from the bench into the bin?If not: Maybe you want to make some research to fix the thing?(Of course: As far as it is possible for you.)I think, it would be a great help for the owners of this unit.Probably most of them are customers, who can't change to an agilent one.Korad left them alone, as you can see...@ Uncle VernonWhat a coincidence...Possibly a bad man would say:" Two heads sharing together one mind - because it's more economic..."I've bought exact this PSU some weeks ago. (The german re-badged version, you know.)Look at this:http://www.electrobi.de/Energie/Netzgeraete-und-Netzteile/Labornetzgeraet-einstellbar/Labor-Netzgeraet-McPower-LBN-305-0-30V-0-5A-regelbar-LCD-Anzeige.html#reviewIt's far away from the league, where the Korad wants to play.But it has one big advantage: It doesn't blow off my connected circuits.Greetings,Hartmut

author: EEVblog
author_rank: Unknown
timestamp: October 30, 2012, 01:17:49 am
content: Quote from: ProBang on October 29, 2012, 11:15:32 pmI sent it back to Trio (it was a loaner after all).I don't want anything more to do with it.Dave.

author: grenert
author_rank: Frequent Contributor
timestamp: November 05, 2012, 02:47:49 pm
content: Quote from: EEVblog on October 28, 2012, 09:40:50 pmCouldn't see that one comingThere's a reason why One Hung Low companies all get lumped together as such.

author: KORAD TECHNOLOGY
author_rank: Newbie
timestamp: November 10, 2012, 07:44:41 am
content: Hello, for KA3005P, Charles has tested and all is excellent. And he will work with Dave to post the good video review very soon.

author: David_AVD
author_rank: Super Contributor
timestamp: November 10, 2012, 08:49:51 am
content: The plot thickens....

author: PA0PBZ
author_rank: Super Contributor
timestamp: November 10, 2012, 09:58:04 am
content: https://twitter.com/eevblog/status/267132540182228992

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: November 10, 2012, 10:27:38 am
content: QuoteGenerally when you see things like "High Grade", "Professional" etc. actually written on a piece of kit it means the exact opposite.

author: Bored@Work
author_rank: Super Contributor
timestamp: November 10, 2012, 10:32:31 am
content: Quote from: KORAD TECHNOLOGY on November 10, 2012, 07:44:41 amCan't wait to see THE GOOD VIDEO. However, I have the feeling you will be a bit disappointed.

author: KORAD TECHNOLOGY
author_rank: Newbie
timestamp: November 10, 2012, 10:53:15 am
content: Quote from: Bored@Work on November 10, 2012, 10:32:31 amThanks for your reply. I sincerely hope I won't

author: tom66
author_rank: Super Contributor
timestamp: November 10, 2012, 11:43:17 am
content: Oh, I think you will.Mwhahahahahahahahaha...I'll go back to my cave.

author: Unknown
author_rank: Unknown
timestamp: November 10, 2012, 01:31:22 pm
content: Quote from: KORAD TECHNOLOGY on November 10, 2012, 10:53:15 amIt will depend entirely upon the performance of your product. Dave will give it a fair call, if the problem is gone and the fix looks permanent you may get something like the review you wish for.Ignore the talking heads in the cheap seats any review will be a fair call of the product as presented.

author: Bored@Work
author_rank: Super Contributor
timestamp: November 10, 2012, 03:47:19 pm
content: Quote from: Uncle Vernon on November 10, 2012, 01:31:22 pmWell, I have the feeling that Dave is not sufficiently motivated to do THE GOOD VIDEO. Asking him to remove the old video (or else?) probably didn't help to motivate him to do THE GOOD VIDEO.

author: grenert
author_rank: Frequent Contributor
timestamp: November 10, 2012, 04:43:14 pm
content: Quote from: mikeselectricstuff on November 10, 2012, 10:27:38 am"Quality Product"

author: tom66
author_rank: Super Contributor
timestamp: November 10, 2012, 04:59:11 pm
content: Clearly the original power supply transistors were completely insufficient for the task and blew up within a few minutes of use.However, I fear that while Korad's modifications may pass the initial "Dave test" (i.e. the power supply works and performs well), they would be no good for long term reliability.You cannot expect to make a decent linear power supply (30V, 5A) with a small heatsink and fan. Insufficient transistors will just make it fail quicker.The only real world test I can think of is leaving it connected to a load at its maximum power dissipation (before a relay clicks in, and at the highst current possible), for several days, and see if it fails. That might give an idea of long-term reliability.

author: T4P
author_rank: Super Contributor
timestamp: November 10, 2012, 06:19:18 pm
content: 1V @ 5A ... That's torture

author: tom66
author_rank: Super Contributor
timestamp: November 10, 2012, 06:57:02 pm
content: Not necessarily, it has a relay clicking in at around 8V, so the worst case would be the greatest voltage drop across the power transistors at full load. Which may occur around 1V, or 9V, or 20V, depending on how it is designed.

author: T4P
author_rank: Super Contributor
timestamp: November 10, 2012, 07:52:36 pm
content: how about 0.1V39.5W is probably pushing the boundaries of what can be done with a aluminium sheet with holes punched in it to resemble a "heatsink"and slightly augmented with a fan that probably only achieves 20+ CFM and some pretty piss poor static pressure numbers.I'm joking though but it can be trueIt seems like this PSU really needs a LGA 775-ish heatsink (The OEM ones) as well as beefier transistors, not wimpy 2N3055s (Is it a 2N3055?) that only costs less than a dollarCan't korad even fork out a few extra ten cents for a beefier transistor?

author: tom66
author_rank: Super Contributor
timestamp: November 10, 2012, 11:17:51 pm
content: This is what it takes to last 30 years. 35V, 3A supply using three Toshiba power transistors plus SCRs to automatically switch in transformer taps (three of them.) Plus an absolutely massive power transformer that's not going to saturate under load.It cost me £30 from a local test equipment dealer, used of course - I'd hate to know what it cost new... It was made in Japan.

author: Unknown
author_rank: Unknown
timestamp: November 11, 2012, 12:20:47 am
content: Quote from: Bored@Work on November 10, 2012, 03:47:19 pmThe feeling eh? Sure it's not a vibe? Feelings are the domain of soothsayers, charlatans, faith healers and other assorted crackpots.QuoteGiven the interest shown in this particular supply, a follow up video would depend mainly on the availability of time and relevant and interesting content.QuoteOr else? There you go having your feelings again. Dave has stated his position on such requests many times, something that has nothing to do with your old countryfeelingsor xenophobiaQuoteI am sure Dave will be overjoyed to think there are nutjobs out there that believe he'd put a desire for retribution before a need to call it as he sees it now. It may not be common practice amongst your secret handshake set but unless you've missed it completely, much of Dave's reputation is based upon his giving no bullshit calls based upon actual results.I'll be interested to see what Korad has done to rectify problems and whether it constitutes a kludge to get it past testing or modification sufficient to give the thing adequate reliability and longevity.Given that Dave will get an actual device and you're working from racial bias, tea leaves and other non specific jiggery pokery don't be offended if those of us with a clue wait for Dave's replies while ignoring your rants. Have a nice day!

author: EEVblog
author_rank: Unknown
timestamp: November 11, 2012, 02:36:28 am
content: My enthusiasm for a new video is almost zip.But if people really want a follow-up, I might put it on the list.Charles has a video of him using the new model for welding or something, as a hack test of it's gruntiness, he will drop it off in a few days and I'll probably put it on my Altzone channel.No point doing another review as such, most of it was done in the previous video. So it would be looking at what they have changed and maybe some thermal and load tests etc.Dave.

author: Unknown
author_rank: Unknown
timestamp: November 11, 2012, 02:51:38 am
content: Quote from: EEVblog on November 11, 2012, 02:36:28 amThat would be the point of interest. Whether the degree of change warrants another video is your call. Are these pieces of wonder a stock item at Trio again? I've seen no mention of them since removal?

author: EEVblog
author_rank: Unknown
timestamp: November 11, 2012, 03:32:23 am
content: Quote from: Uncle Vernon on November 11, 2012, 02:51:38 amNo, Charles is still waiting for replacement boards for the existing units he has in stock.Dave.

author: Bored@Work
author_rank: Super Contributor
timestamp: November 11, 2012, 07:26:49 am
content: Quote from: Uncle Vernon on November 11, 2012, 12:20:47 amYou know, in the US they sometimes say someone is two fries short of a happy meal. I think you are two test leads short of a multimeter. And two shrimp short of a barbie , if you get the drift.

author: rr100
author_rank: Frequent Contributor
timestamp: November 11, 2012, 08:59:35 am
content: Quote from: EEVblog on November 11, 2012, 02:36:28 amI'm interested, if we are to prioritize just behind the USB/portable/etc power supply progress report (assuming there is some progress).Of course, all of them are coming behind the vids with Colin Mitchell and Doug Ford, but I assume those just one-off sort of things.

author: Unknown
author_rank: Unknown
timestamp: November 11, 2012, 09:21:31 am
content: Quote from: Bored@Work on November 11, 2012, 07:26:49 amMaybe, but you're going to tell me right?QuoteThat is nice for them! In Borneo folks likely say something entirely differentQuoteThere is your mistake, you've kidded yourself that others, let alone my good self five a flying fourex what you think.Was it one of your flying generalisations like "all Asians are thieves" or some other manic rambling? You can answer if ou like just don't assume anyone is listening.We can reasonably conclude you have nothing of use or interest to offer on this topic..

author: EEVblog
author_rank: Unknown
timestamp: November 11, 2012, 10:36:11 am
content: Quote from: rr100 on November 11, 2012, 08:59:35 amColin was a one-off, he's in another state.Doug will be back with a quite a few episodes.Dave.

author: Bored@Work
author_rank: Super Contributor
timestamp: November 11, 2012, 11:08:31 am
content: Quote from: Uncle Vernon on November 11, 2012, 09:21:31 amCould you at least be a bit original and funny? I mean, just for once? Repeated racism accusations? How boring.

author: Unknown
author_rank: Unknown
timestamp: November 11, 2012, 11:21:24 am
content: Quote from: Bored@Work on November 11, 2012, 11:08:31 amFor you? Lemme see? Na, Nup, nada, not worth it!QuoteWhat you're not laughing? Must be taking yourself seriously again. That gives others a giggle and for that we thank you.Quotemust be in response to repeated racism. hmm?

author: KORAD TECHNOLOGY
author_rank: Newbie
timestamp: November 11, 2012, 11:43:32 am
content: Quote from: Uncle Vernon on November 10, 2012, 01:31:22 pmHello, Uncle Vernon, thanks a lot for your support.I also believe Dave will give a fair call. Charles has made a good video and will post next week after he gets the repairing boards for his current 16PCS stock. Have a nice evening!

author: Bored@Work
author_rank: Super Contributor
timestamp: November 11, 2012, 11:55:00 am
content: Quote from: Uncle Vernon on November 11, 2012, 11:21:24 amNo sorry kid, you lost your drive when you started to resort to spelling error correction postings to establish your superiority. And then you come up with racism accusations. Carefully chosen because it is nearly impossible to defend against such an accusation. By the way, did you clear that one with the leader of my fan club, Private Fluffer? He might be a bit upset if you didn't run it by him before posting.By the way, have fun with a response. Guess what I'll do with it?

author: Unknown
author_rank: Unknown
timestamp: November 11, 2012, 12:01:18 pm
content: Quote from: KORAD TECHNOLOGY on November 11, 2012, 11:43:32 amI am not offering any particular support other than a sense of fair go, if the modifications to your supply are sufficient, I can see no reason why some of the initial enthusiasm for it cannot be revived.I trust calls Dave or Charles will make and see it as ignorant that some will condemn on no basis other than country of origin. There is interest, by some, in a follow up video, but as always it will be Dave's call what is produced and released.

author: Unknown
author_rank: Unknown
timestamp: November 11, 2012, 12:11:37 pm
content: Quote from: Bored@Work on November 11, 2012, 11:55:00 amHaven't heard that one this century. Almost a compliment,QuoteIt is heartening to see you have recognised this superiority, but there is no need for you to make any fuss, if you bow as I enter the room and covet your eyes, that will be entirely sufficient.QuoteA perfectly reasonable response towards repeated racism..QuoteIt will be given your repeated racist remarks are embedded in all manner of caches and backups by now.Quote from: Bored@Work on July 20, 2012, 02:54:36 pmQuoteIf this is a lead-in to another of your rectal activities posts, then I'll choose not to guess thanks all the same.Be nice to others.

author: LaurenceW
author_rank: Frequent Contributor
timestamp: November 11, 2012, 12:34:54 pm
content: I imagine that BAW's bed is up on six foot stilts, so that, whichever side he gets out of it, it's always thewrongside and leaves him fuming at the rest of humanity for the whole day, as a result.I reckon

author: KORAD TECHNOLOGY
author_rank: Newbie
timestamp: November 11, 2012, 01:56:22 pm
content: Quote from: george graves on July 20, 2012, 12:11:26 amHi George, it is an early shipment(NOT a flaw) due to a few defective transistors. And now this issue has been fixed. The units sent to our other representative are good and sell well. After Charles (Trio Smartcal) gets the boards to fix his current 16PCS stock, you can buy from him.Thanks for your support in advance!

author: Bloch
author_rank: Unknown
timestamp: November 11, 2012, 08:58:33 pm
content: Quote from: KORAD TECHNOLOGY on November 11, 2012, 01:56:22 pmIs that the transistor on the back pcb ? Or are there more ?Quote from: KORAD TECHNOLOGY on November 11, 2012, 01:56:22 pmThis is great! Can you upload here the old and the updated service manual (with schematic) ? So we can see that is updated ?

author: TRIO_Smartcal
author_rank: Contributor
timestamp: November 13, 2012, 06:29:49 am
content: Hi everyone, I received the modified power supply from Krissy at Korad just over a week ago. So the first thing to do was to try and blow it up or burn it out to appease the trolls and for the interest of the more curious folks watching the thread. In a nutshell I failed. The thing is still sitting beside me here with its output current-dependent fan going flat out.What it was subjected to was:- Set to 31.00V 5.100A and shorted the output. Left running for about 3 hours.- Output shorted and the output switched on and off rapidly- tried to use it as an arc-welder to stick the DMM probe to an alligator clip- ran it at close to 150 Watts for about 5 hours- rapidily switch the output on/off set to 31V 5.1A and a load connected- ran it at 1V, 5.1A into a short circuit for 3 hours (this was more interesting from the current measuring DMM perspective...)In summary, as we say here in Aussie-land the results were "as boring as bat-sh*t." The thing is still working. I have never seen bat-sh*t, but I can endorse the validity of the adjective used in the comparison to a working power supply in steady-state conditions.I did get that nice smell of warming plastic from the insulation on the alligator clips connected to the load. But nothing more spectacular than that.I took a few thermal images of it too. Before I get trollisitc comments.. these were taken with the cover on because the cover forms part of the forced air cooling path. Highest temp I could see was about 77 degC on the transformer when it had been running at full load for over 2 hours. I'll upload those thermal images in the next post.The one in this post is the power supply feeding the 10A input on a DMM. It did this continuously for over 3 hours today and had no problems with being switched on and off rapidly. You can see the area on the DMM where its fuse sits just behind the front panel. You'll see in the video, whenever I get it loaded, that this warming affects the DMM reading. And before anyone comments, the DMM's had auto-powered-down and I'd got bored turning them on over and over again.

author: TRIO_Smartcal
author_rank: Contributor
timestamp: November 13, 2012, 07:13:59 am
content: Here's some of the thermal images taken after the Korad KA3005P had been running for a while.In the process I tried a couple of DMM's for the current measurement to see which warmed up the most and to see if it was possible to see where the internal shunt and fuse was without opening them. I'd got bored with the power supply at this stage.Anyway, I couldn't blow it up so when we get the parts to repair those we have in stock, they will go back on sale with a 2 year warranty. If anyone wants to buy one, just mention EEVblog and we'll chuck-in at no charge a set of DMM test leads so you can use your old ones as welding rods....http://triosmartcal.com.au/1713-tl-104-test-leads--alligator-clip-cat-iv-600v--cat-iii-1000v.html

author: TRIO_Smartcal
author_rank: Contributor
timestamp: November 13, 2012, 07:55:29 am
content: The warmed up DMM's are in the thermal pic's below. These were an Agilent U1233A and an Agilent U1241A. I used a U1252A to keep an eye on the voltage.During the soak-testing the current reading on the DMM's used to measure current steadily increased as they warmed up.The power supply current reading did not change much at all. The voltage reading crept up marginally.As most of you are probably aware, a DMM measures current by measuring the voltage over an internal shunt.So what we were seeing with the slowly, but steadily, increasing reading on the DMM's was the internals of the DMM's getting warm, the internal resistance increasing with this temperature rise and the power supply giving a bit more voltage to keep the current at max. The test leads will also play a part in this resistance path. We can see that the resistance of the leads and the DMM input is a combined 0.1 Ohms.The normal picture below shows the DMM after it had been running for a while and the current reading had drifted up a bit. This was while we were testing at a setting of 1V, 5.1A. The power supply went to constant current mode to deliver its max current and the compliance voltage necessary for this (0.5465V) is displayed on the U1252A.It would have been more interesting if it hadn't all behaved as expected, but all ended up as hoped for.We still have a working power supply and I got to play with a thermal camera.......

author: EEVblog
author_rank: Unknown
timestamp: November 13, 2012, 09:15:17 am
content: Awesome follow-up, thanks Charles!Dave.

author: SeanB
author_rank: Super Contributor
timestamp: November 13, 2012, 05:00:08 pm
content: Are you going to send a board to Dave to do his unit? Will be interesting to see the comparison and how it looks.

author: Bloch
author_rank: Unknown
timestamp: November 13, 2012, 05:03:36 pm
content: Quote from: SeanB on November 13, 2012, 05:00:08 pmNot possible - Dave send it to hell or there about[size=78%]

author: TRIO_Smartcal
author_rank: Contributor
timestamp: November 13, 2012, 09:43:38 pm
content: Dave sent the blown-up unit back here. Whenever we get the parts from Korad to fix it I'll take a few pics of any modifications and post them here.

author: EEVblog
author_rank: Unknown
timestamp: November 14, 2012, 11:56:14 am
content: And here is Charles's video of of testing the new supply:Looks pretty comprehensive, and if that abuse didn't kill it, I'm not sure what will.Nice work Charles!Dave.

author: nitro2k01
author_rank: Frequent Contributor
timestamp: November 14, 2012, 12:30:43 pm
content: Quote from: EEVblog on November 14, 2012, 11:56:14 amMy own personal theory is that the error condition in the original test was produced by a race condition with the load. For example, the load is able to repeatedly overload and de-overload the supply very quickly such that the total current that passes through the supply through multiple pulses is enough to destroy something. Or, there's a comparator which triggers an interrupt on the microcontroller, which is triggered multiple times. This makes the microcontroller's interrupt stack to overflow, or something like that.My point is, I would want the same scenario, with the electronic load, to be tested before giving the new unit the thumbs up.

author: SeanB
author_rank: Super Contributor
timestamp: November 14, 2012, 12:43:57 pm
content: Send it through the postal service wrapped in brown paper, that will destroy it.Nice test, though I would like to see it being run until it does a thermal shutdown into a short circuit or into a 12V lamp in CC mode.Is it me or does the micro stop scanning the display when changing voltage, leaving an arbitrary digit running at full power while doing so. It would be better for the firmware designer to blank the display when doing this, to keep from burning out the display digits.

author: Stephen Hill
author_rank: Regular Contributor
timestamp: November 14, 2012, 12:59:11 pm
content: Quote from: AcHmed99 on November 14, 2012, 12:53:06 pmKIA's come with a 7 year warranty...

author: deephaven
author_rank: Frequent Contributor
timestamp: November 14, 2012, 01:10:55 pm
content: One of the most important specs on a lab power supply for me is to never overshoot the set output voltage so as to avoid zapping the circuit it is powering. Would it be possible to do some of those tests with a scope attached?

author: HackedFridgeMagnet
author_rank: Super Contributor
timestamp: November 14, 2012, 01:30:19 pm
content: QuoteI agree with Nitro. I think.When I saw the video of the fault occurring, I had a thought along the same lines, ie. Constant watt load (if I remember rightly) and some sort of diverging control interaction going on between the two units.Reproducing the circumstances of the failure so the new version could be tested under these circumstances would be a good validation of any fix.If anyone could be bothered.

author: george graves
author_rank: Super Contributor
timestamp: November 14, 2012, 05:14:13 pm
content: A follow up would be nice.

author: TRIO_Smartcal
author_rank: Contributor
timestamp: November 14, 2012, 11:03:35 pm
content: Quote from: Stephen Hill on November 14, 2012, 12:59:11 pmIf you'd like me to raise the price to that of a Kia you can have a 99 year warranty

author: TRIO_Smartcal
author_rank: Contributor
timestamp: November 15, 2012, 04:59:08 am
content: Dave has posted a very amateurish video about our attempt to burn-out the Korad version 2.It's a summary of the attempt. Obviously the video does not show the 12 or so hours we had it running for during the burn-out test.Here's the link:http://www.eevblog.com/2012/11/15/korad-psu-follow-up/If you fall asleep during it that's OK, it's a power supply after all. No car headlamp bulbs or items of test equipment were injured in the making of this video. We tried though.......

author: BravoV
author_rank: Super Contributor
timestamp: November 15, 2012, 05:24:09 am
content: What happened to other customers who bought this thing say from ebay type of deal ?So practically they're screwed ?

author: george graves
author_rank: Super Contributor
timestamp: November 15, 2012, 05:42:26 am
content: How can we tell the difference? between the old model and the new "fixed" models? I'm in the US - and would prefer to buy from a US seller.

author: pickle9000
author_rank: Super Contributor
timestamp: November 15, 2012, 07:18:14 am
content: Quote from: TRIO_Smartcal on November 15, 2012, 04:59:08 amWhat kind of load for the burn in?

author: TRIO_Smartcal
author_rank: Contributor
timestamp: November 15, 2012, 07:25:02 am
content: A car headlamp. See here.....http://www.eevblog.com/2012/11/15/korad-psu-follow-up/Watch at 5 minutes in.

author: TRIO_Smartcal
author_rank: Contributor
timestamp: November 15, 2012, 07:52:00 am
content: Quote from: BravoV on November 15, 2012, 05:24:09 amI can only speak for Australia and NZ but all I can suggest is that you go back to where you bought it from if you have a problem. These things have different transformers for the supply voltage (as we are told) so the 110V USA version might be OK.We have had 2 failures here, one being the one we loaned to Dave and a unit we had sold. We contacted the people we had sold the others to and recalled them because the risk was too high with the nature of the fault if they blew up - pumping out 46V approx I seem to remember. We offered customers another power supply on the link below as a no-charge replacement or they could wait for a fix. They could get the same volts and amps from the replacement and they are linear too. No one was using it as a programmable anyway which made it easy.http://triosmartcal.com.au/dc-bench-supplies/2432-atten-aps3003s-3d-dual-power-supply-0-30v-3a.htmlIf there hasn't been a lot of reports from elsewhere about units blowing-up then it could be that we indeed got a dodgy batch and/or the Aussie mains supply voltage (typically around 240V-245V in the main metropolitan areas) was sufficient to let the smoke out of whatever they are using as a regulator.It's interesting to see the amount of visibility this unheard-of low-cost power supply has received compared to some far more interesting products on the blog, but I think a lot of it stems from:a) what it is specified to do for the price andb) the intrigue generated about what was going to happen after it blew up.There's a post here that addresses the type of questions/comment like yours referring to "screwed."There is a way to avoid being screwed by choosing not only on price. It's value and the elements that comprise it that matter.https://www.eevblog.com/forum/blog-specific/eevblog-359-qdso-pocket-oscilloscope-review/45/I suggest Krissy from Korad answers this next question.Quote from: george graves on November 15, 2012, 05:42:26 amThere is probably a range of serial numbers from this bad batch that should be known by Korad. I can't imagine there are only the 16 units we have here in the batch. So to use those timeless words... they are out there... However I refer back to the supply voltage issue and if you are on mainland Europe you might just be OK. If you are in the UK you might have a potential issue. The first units we received had 220V on the label on the rear. The one we can't blow-up has 240V on the label. That I suggest is significant. But Krissy @ Korad needs to answer this question and Krissy can also give you the name of their USA distributor if they have one.

author: TRIO_Smartcal
author_rank: Contributor
timestamp: November 15, 2012, 12:00:31 pm
content: Quote from: SeanB on November 14, 2012, 12:43:57 pmActually we ran it for a couple of hours with the filaments in parallel. The setting was max amps & max volts. It went into CC mode just the same as it did with output short circuit. Nothing happened. The compliance voltage was around 4.5V I think. The lamp just glowed as the filaments in parallel were sharing the 5.1 amps so their combined parallel resistance was still low hence the low voltage. Was so boring I didn't bother including it. I've got a bit of video though if anyone is desperate to see it. The big takeaway was just what a flexible load a head lamp bulb really makes :-)

author: TRIO_Smartcal
author_rank: Contributor
timestamp: November 15, 2012, 12:20:04 pm
content: Quote from: AcHmed99 on November 14, 2012, 12:53:06 pmActually I didn't care about the cost of the time. Sometimes you put this sort of stuff before dollars per hour. I wanted to know as much as everyone else if it worked or not. If it was purely a commercial decision I would have scrapped the dodgy stock months ago and did something else. Given the effort put into this even if we fix them all we probably won't recover the full time and opportunity cost. It`s also why I did a lot of it after beer-o-clock in the evening. If you closely look at the state of the alligator clip and DMM probe in the short circuit test you'll see that they are very burnt already. Before I took the video I knew this thing was OK. Hours spent for fun and interest and not gain. Hope that addresses your point.

author: JackOfVA
author_rank: Unknown
timestamp: November 15, 2012, 12:28:53 pm
content: For a quick and dirty intermittent short circuit test setup, use an old file and a nail. File to one side of the PSU, nail to the other and run the pointed end of the nail along the file.Should see a bunch of sparks and a nasty looking current/voltage waveform.Jack

author: TRIO_Smartcal
author_rank: Contributor
timestamp: November 15, 2012, 02:34:26 pm
content: We have a temp/humidity chamber in the cal-lab. I can assure you this is going nowhere near it. We are not a company driven by bean-counters but I think we have done enough on this now.

author: David_AVD
author_rank: Super Contributor
timestamp: November 15, 2012, 08:39:47 pm
content: Let us know when they are back on the shelf and ready for sale. I'm still interested in one (maybe two).

author: TRIO_Smartcal
author_rank: Contributor
timestamp: November 15, 2012, 09:09:17 pm
content: When we get the parts off Korad I'll put a post here. Hopefully it will not be too long.

author: TRIO_Smartcal
author_rank: Contributor
timestamp: November 27, 2012, 12:20:17 am
content: Quote from: David_AVD on November 15, 2012, 08:39:47 pmQuick Update - The new output boards have been dispatched by Korad. We are closely following the DHL shipment. As of posting they are in the air between HKG and SYD. We'll make another post here when they are back on sale after we have swapped the boards over and given the power supplies a bit of a work-out. We will have 16 units available then ex-stock Castle Hill (Sydney).

author: johnboxall
author_rank: Unknown
timestamp: December 04, 2012, 11:19:21 pm
content: And they're back:http://triosmartcal.com.au/2647-ka3005p-programmable-dc-power-supply.html

author: grenert
author_rank: Frequent Contributor
timestamp: December 05, 2012, 12:11:54 am
content: It looks like a little of Trio's QC costs are finding their way into the price

author: tom66
author_rank: Super Contributor
timestamp: December 05, 2012, 02:02:25 am
content: Also, there is no mention of the items being refurbished... I mean, they are better but the consumer doesn't know that from the product page.

author: george graves
author_rank: Super Contributor
timestamp: December 05, 2012, 02:24:53 am
content: Quote from: tom66 on December 05, 2012, 02:02:25 amI wouldn't consider fixing a problem before sale "refurbished" - since these aren't returns - they are new.And I can't imagine anyone being upset that a flaw was fixed before it was shipped to them. Unless you just like to complain about things.Is there a person to contact at Korad to find out what range of serial numbers have this problem and how it effects the US market 110 volt models? You know....for us in the states that want to pick one of these up?

author: tom66
author_rank: Super Contributor
timestamp: December 05, 2012, 02:51:40 am
content: Eh, some people might care that they're not entirely original. Lawsuits have been made over less.I don't care, just making a point.

author: TRIO_Smartcal
author_rank: Contributor
timestamp: December 14, 2012, 08:45:24 am
content: Quote from: tronixstuff on December 04, 2012, 11:19:21 pmThey're back and they are sold at $195+GST. The web-guy didn't bring the price down when it was put back up there.We've had one running for over a week now powering a car headlamp, both filaments in series at 30V across them. All was well. It got a bit warm and there was a strange glow from my garage. Did it on a concrete garage floor just in case...The other tests we did are here...http://www.eevblog.com/2012/11/15/korad-psu-follow-up/As for TOM66's comments, these are sold as new. If you were in the process of buying a car and the dealer rectified a manufacturing defect before it was sold, it is not classed as used or refurbished. It is still new. This is no different. The warranty is as new.Cheers folks!!

author: Scopeman1
author_rank: Contributor
timestamp: December 15, 2012, 12:58:26 am
content: Quote from: george graves on December 05, 2012, 02:24:53 amA Korad person made some comments earlier. Perhaps if they are reading this they could give us the serial number range?

author: Rick
author_rank: Frequent Contributor
timestamp: December 31, 2012, 07:49:26 pm
content: By the way the ones sold on ebay are switchable between 110V and 220V.I have also asked the question to SRA Soldering Products on Amazon.com, waiting for an answer.On Amazon.com the prices are half the level in Australia and they ship by USPS priority mail.

author: TRIO_Smartcal
author_rank: Contributor
timestamp: January 01, 2013, 12:32:47 am
content: Just be careful of the 220V instead of 240V transformer. I suspect there's little tolerance in the regulator design for handling much above the rated power.Remember power is V^2/R and when you square 220V and 240V and compare, assuming a similar resistance, then power dissipation requirement goes up by 19%. The ratio is the same on the LV side.Just food for thought but we know what happened to the 220V version we had. Given that in Metro areas of Australia the mains voltage is typically in the low 240's, personally I would not take the risk using a 220V version here in Aussieland.

author: Rick
author_rank: Frequent Contributor
timestamp: January 01, 2013, 12:51:30 am
content: Quote from: TRIO_Smartcal on January 01, 2013, 12:32:47 amWell I think the nominal mains voltage here in Turkey is 220V although I have seen variations between 215V and 235 V, but I think it is around 220V. I have just measured it right now with 3 different multimeters. It is 229V-231V...My $70 power supply is meant to work with 220V+/-5% and this falls within these limits. No problem so far. What is the tolerance for KORAD as far as the mains voltage is concerned?

author: Rick
author_rank: Frequent Contributor
timestamp: January 02, 2013, 03:55:52 am
content: By the way I watched the follow up video by Altzone. Is it better to use a 240V device if we live in an area where the mains voltage fluctuates between 215-240V? Actually it is mainly around 230V, I measured again.

author: TRIO_Smartcal
author_rank: Contributor
timestamp: January 02, 2013, 07:55:22 am
content: I don't think there is a simple answer to your question.With these Korad's there seems to be two types of transformers. There is a 220V transformer that has a centre tap for 110V operation and a 240V transformer with no centre-tap so fixed 240V nominal operation.From what I can see in the pictures that 110/220V unit has definitely got the new version boards. Plus it has a transformer labelled 220V. Those are the same boards as we received as replacements to upgrade our stock. If there are two transformers needed (especially one for 240V operation), then that would indicate that the regulator board does not like too high a supply voltage.The Korad's tolerance on mains-voltage does not seem to be specified on any documentation we have so it is difficult to to pass comment on your question. All I can do is reiterate that if something is designed for 220V and here in Australia it can go to 253V and still be in tolerance, then I personally would not take the risk.Here's an interesting bit of reading. The first paragraph 2.2.1 says it all........http://users.metro2000.net/~purwinc/seec2_2.htm.The supply voltages were "harmonised" around many countries in the 220V-240V world, however all they did was really change the tolerance. This allowed authorities to say 230V is the standard but power companies can continue using all their old 220V and 240V generation and distribution systems. The way the voltages are now specified, means all will be still compliant but manufacturers have to build to that requirement if they wish to send the same products to multiple markets. This does not seem to be the case with KORAD.If you are in an old 220V country (now nominally 230V), and as you said Rick, your typical range is 215 to 235 then you haven't got a huge risk if you get the 110/220V version..... HOWEVER..... and here's the crucial issue, Korad needs two transformers depending on the destination. Why would they need to do this? Think about it because that's the $200 question....So it's up to individual's choice to buy one with a 110/220V transformer and take the risk using it where theTYPICALvoltage is >240V like in Australia and UK, (old 240V countries before "harmonisation"). All I can say is that if you are in an old 240V country and buy a 240V version then you also are probably OK.The remaining question is "if you are in an old 220V country and you get a 240V version, (as you are suggesting Rick) will there be enough voltage from the mains supply, if it is at the low end of its tolerance (around 215V), to allow the power supply to deliver its full rated output voltage under full load....??"I suddenly feel a variac moment approaching...... but not now as "beer o'clock" is only 4 minutes away...

author: IanB
author_rank: Super Contributor
timestamp: January 02, 2013, 09:44:07 am
content: One question for Korad is why not just build the thing with a 120/240 V transformer and avoid the need for two transformers? This ought to work fine as the USA and many parts of the world are nominally 120 V regions. If 240 V could over-volt a 220 V supply, then 120 V could similarly over-volt a 110 V supply.

author: BravoV
author_rank: Super Contributor
timestamp: January 02, 2013, 10:00:04 am
content: Quote from: IanB on January 02, 2013, 09:44:07 amUsually its just the matter of dumping the excess cheap stock (fixed volt version) from the transformer manufacturer or in their own warehouse, just don't expect components/parts consistency from this kind of company.

author: pomonabill221
author_rank: Frequent Contributor
timestamp: January 26, 2013, 08:05:21 am
content: I just bought a Korad 3005P supply, and following in my and Dave's footsteps, the first thing I did was take it apart!I wanted to see if it was the new and improved version (the seller said it was... I need to make sure), and it is!1) There is a 110/220v selector switch on the back.2) The usb/serial board is the new one (choke on the board, NOT in the wiring from the transformer).3) The output board is the green not the white material... (glass and not linen, cheap board).Or course, I had to do MORE investigating.....One thing I found that I did NOT like is the FWB was NOT bolted to the heatsink, but relied on the stiffness of the leads (they are very heavy) to hold it to the heatsink... BAD!!!! so I pulled it apart, drilled a hole in the heatsink to pull it down to the aluminum, and did some minor bending to relieve some of the stress on the leads.This, I thought, was pretty bad as the FWB is going to get hot. It did have heatsink goop on it, but it wasn't flush! I took pictures of this as well.Then, I looked at the output transistors... they are 2sd1047... they are 120volt/12amp max, BUT ONLY 100watt max! Seems a little close as far as dissipation.There are two transistors and each one has a balancing resistor in it's collector so that they share the load.There are two relays that switch the different secondaries... I measured (no load) the V+ bus and when the relays switch.between 0 - 7v the bus is 17.4v" 7.3 - 14.0 bus is 35.0" 14.1 - 21.5 bus is 43.4 (sound familiar???)" 21.5 - 31.0 bus is 58.5 (once again, sound familiar???)The voltages between the four respective transformer leads are:blk - white 32.5 vacblk - red 43.5 vacyellow - white 15.15 vacyellow - red 26.3 vacThese are the combinations that the relays switch.I didn't try the same test with a load, but I would imagine the relays may switch at different output voltages depending on load to keep the delta across the outputs within a range for regulation.I also haven't looked at the turnon but that will be my next test.The software is a little clunky but the ability to setup timed voltage stepping with different current limits is sort of nice for cycle testing... only thing is if the cycle is started and you stop it, you cannot restart it from time zero... it just continues from where you stopped it... NOT good!Overall... for me, and the price and programmability, I am happy.... I have use HP supplies before (I used to work at Hughes Aircraft), and I do have a couple of Lambda bench supplies that are HEAVY and big, but this one will do what I want and hopefully won't fail like Dave's did.

author: T4P
author_rank: Super Contributor
timestamp: January 26, 2013, 10:12:36 am
content: Little close? Nah. If there are 3 taps it only needs to dissipate 50W, in any case any more than that results in requiring a MUCH larger heatsink anyway

author: pomonabill221
author_rank: Frequent Contributor
timestamp: January 26, 2013, 08:23:17 pm
content: Quote from: T4P on January 26, 2013, 10:12:36 amYes you are right... after I posted this I thought about what I said and realized that this is one of the reasons they have the four different bus voltage selections, to keep dissipation down, use small heatsink, "cheaper" transistors, smaller ballast resistors, etc.One thing I am going to test is when the relays switch (changing voltage setpoint), does the output bounce around? (this is a question that I am going to try and resolve).Another thing... when switching the output on, is the relay switching causing the overshoot on turn on (another question I am going to try and answer)?This would indicate to me that the output should be enabled FIRST, then applied to the binding posts after a short delay (after the supply has settled), and I might just makeup a delay to do this so I don't cook something from the turn on overshoot.

author: george graves
author_rank: Super Contributor
timestamp: April 24, 2013, 12:15:55 am
content: For USA folks. SRA solder has these on sale for $95 shipped on ebay today.http://www.ebay.com/itm/KORAD-PROGRAMMABLE-PRECISION-VARIABLE-30V-5A-DC-POWER-SUPPLY-DIGITAL-LAB-GRADE-/110888868115?pt=LH_DefaultDomain_0&hash=item19d17dd913The ebay user id is randyruby - but it's SRA solder.I couldn't resist - I order two.

author: hgg
author_rank: Frequent Contributor
timestamp: May 14, 2013, 08:27:01 am
content: Hi,I would like to buy a bench power supply and I think I will buy the programmable Korad.http://www.ebay.com/itm/110888868115Apart from the stability problems that they are supposed to be fixed, I've seen some caseswere the main power on/off switch has failed. Do you know if they have fixed that as well?Some questions for the owners of this power supply:- Is it silent? Is the fan always on, or only when needed?- Does it make any hissing noises with a load or without one?- Does it have any overshoot problems?I am already over-budget by buying this power supply. Do you think its a good option forthe money? Are there any better ones for a similar price? (not used ones)Thank you!

author: iloveelectronics
author_rank: Frequent Contributor
timestamp: May 14, 2013, 08:44:00 am
content: Quote from: hgg on May 14, 2013, 08:27:01 amTry the Vantek 3305P instead. There was a thread on this PSU some time ago:https://www.eevblog.com/forum/reviews/vantek-dps-3305p-32v5a160w-programmable-dc-power-supply/It doesn't overshoot, and it actually has 5 preset buttons for M1 to M5, and they work as they are supposed to. I read before that the Korad's presets don't really work the way they should, you could change the settings even without overwriting them explicitly.

author: hgg
author_rank: Frequent Contributor
timestamp: May 14, 2013, 09:17:21 am
content: ...but do you know where can I buy the Vantek from?(I live in Greece).

author: iloveelectronics
author_rank: Frequent Contributor
timestamp: May 14, 2013, 10:03:28 am
content: Quote from: hgg on May 14, 2013, 09:17:21 amHere's one on eBay:http://www.ebay.com/itm/Programmable-Variable-Adjustable-DC-Power-Supply-0-32V-0-5A-USB-AC-110-220V-/281101170639?pt=LH_DefaultDomain_0&hash=item4172ef77cfBut make sure you confirm with the seller you're getting the Vantek or Caltek branded ones. Apparently identical looking units with a different brand name do overshoot.I have also sourced a couple of these for another forum member some time ago. The one I bought for my own use very recently seems to look different internally though, perhaps they have revised the design since that discussion thread above in 2011.

author: hgg
author_rank: Frequent Contributor
timestamp: May 14, 2013, 11:09:33 am
content: Hi, thanks I will check that out, although it ships from China...So do you mean that the Konrad is a re-branded Vantek

author: hgg
author_rank: Frequent Contributor
timestamp: May 14, 2013, 11:36:26 am
content: I also saw in the photos that the Vantek has a toroidal transformer.I assume that this is better, correct?

author: iloveelectronics
author_rank: Frequent Contributor
timestamp: May 14, 2013, 01:22:28 pm
content: Quote from: hgg on May 14, 2013, 11:09:33 amAs far as I know, no, they are manufactured by different companies.

author: iloveelectronics
author_rank: Frequent Contributor
timestamp: May 14, 2013, 01:41:20 pm
content: Quote from: hgg on May 14, 2013, 11:36:26 amI think there are pros and cons, but I'll leave this to the more qualified and knowledgeable members to answer.

author: hgg
author_rank: Frequent Contributor
timestamp: May 14, 2013, 07:08:24 pm
content: In the case of the Korad, I can only find the one with the 220V transformer.I've heard that there is a version with a 240V transformer as well.Here in Greece we have 230V. Do you think I will have any problems?Thanks.

author: madires
author_rank: Super Contributor
timestamp: May 16, 2013, 08:16:54 pm
content: Quote from: hgg on May 14, 2013, 07:08:24 pmShould work fine since a proper PSU is designed to run with 10% under/overvoltage.

author: hgg
author_rank: Frequent Contributor
timestamp: May 16, 2013, 09:53:14 pm
content: Just bought it.... Thanks.

author: nelsonro
author_rank: Newbie
timestamp: May 24, 2013, 02:24:50 pm
content: Found a different kind of fail with a re-branded tenma psu... if you look at the model it says 2x3Aoutputs + 1 fixed 5v rail but this unit its a 2x5Aoutput with no extra 5v rail lets just hope they didin't just flash the wrong firmware in itto make it go to 5a.didn't notice at the time but this one doesn't have pc connection.Also tldr all so don't know if anyone found how to go to m5... actually found it by accident, just press m4 and rotate the adjust knob clockwise

author: leniwiec
author_rank: Contributor
timestamp: January 06, 2014, 10:52:49 pm
content: I also have two of them, and now warranty for them had ended, so I decide to make it less noisy ;-) If somebody interest, take a look on my ultra simple hack herehttp://www.leniwiec.org/en/2014/01/06/korad-ka3005d-silent-fan-hack/Cheers!

author: pomonabill221
author_rank: Frequent Contributor
timestamp: January 07, 2014, 01:48:13 am
content: Took a look at your mod (not really a hack though) and left you a comment. Nice work and I just might do the same.My supply may be a later one though as on the heatsink, every other finger is bent over so the air must pass by the fingers.I have had the thermal trip the supply due to overheat, so a larger heatsink seems to be the way to go!

author: leniwiec
author_rank: Contributor
timestamp: January 07, 2014, 03:52:26 am
content: Thx pomonabill221. Yes, it is nothing big, I just wrote about it because want to share my opinion about this units

author: pomonabill221
author_rank: Frequent Contributor
timestamp: January 07, 2014, 03:57:27 am
content: Thanks!Quote from: leniwiec on January 07, 2014, 03:52:26 amThanks! Yes it is a cheapy and has "limited" performance, but it isn't an HP/Agilent/Lambda and it doesn't have the price tag either! Just remember that when using it (really a comment to everyone).

author: GiskardReventlov
author_rank: Frequent Contributor
timestamp: January 31, 2014, 10:55:50 pm
content: A general question about the testing process. I've seen this in other videos here too. Dave had his BK connected to the Korad. No doubt I'm missing some basic knowledge here. Why did he have power going in to a power supply? I know he touched on this but I didn't get it. It seems this was important to revealing the failure, right?

author: jancumps
author_rank: Unknown
timestamp: January 31, 2014, 11:04:23 pm
content: Quote from: GiskardReventlov on January 31, 2014, 10:55:50 pmThat device can sink power. He uses it as a configurable load.

author: GiskardReventlov
author_rank: Frequent Contributor
timestamp: January 31, 2014, 11:12:39 pm
content: Quote from: jancumps on January 31, 2014, 11:04:23 pm"That device" == "He uses it" == BK?If my understanding's correct above, you're saying that the BK can handle power in either direction. Is that right. It can act as a multimeter. I think he said that in the video but I wasn't clear on that. I think he did same in the Rigol DP832 video (which also had serious issues).If my understanding's not correct of what you meant, then what did you mean?

author: jancumps
author_rank: Unknown
timestamp: January 31, 2014, 11:17:13 pm
content: Quote from: GiskardReventlov on January 31, 2014, 11:12:39 pmIt is a programmable load. So you can configure the amount of load it will apply to the source." A configurable consumer of energy "

author: GiskardReventlov
author_rank: Frequent Contributor
timestamp: January 31, 2014, 11:29:54 pm
content: Quote from: jancumps on January 31, 2014, 11:17:13 pmThat makes a lot of sense, thanks!I would never spend money on this Korad. Dave is a good man, because this thing is a disaster and I believe he was being quite generous to Charles and Korad. Maybe Korad shoud be looking for new hires. There are literally millions and millions of college graduates in China looking for work.Now I will go look to see if he reviewed any legacy PS that can be found for low $, these new low $ supplies are too much crap. Buying one at any price encourages them to keep making them. Dave's become their personal Quality Control engineer.

author: jancumps
author_rank: Unknown
timestamp: January 31, 2014, 11:56:13 pm
content: It depends on what you need. My PS is crappier than that Konrad and it serves me well.As long as you know the limits, and the limits don't stop you from doing your work...

author: pomonabill221
author_rank: Frequent Contributor
timestamp: February 01, 2014, 12:00:44 am
content: The version of the Korad that Dave destroyed is an old one and Korad has upgraded the supply (the output transistors).You really need to do a little more research on the supply before you completely write it off and call it crap.Yes it is a cheap supply, but for what it does, and for what it costs, it is ok for most.I have two Lambda supplies (an LQ-531 ( 20v/8.6amp and LQ=533 60v/3.3amp) and they are tons better than the Korad, BUT are about 3x heavier and at least 2x larger. For my testing, I use the Korad and knowing the limitations and faults, the Korad is just fine.If you want to be a brand snob... so be it, so good luck finding a "good" supply for around 100 that is remotely programmable.Did you even bother to look at the schematic and understand what is going on? May be educational as well.Seems strange that you are bashing the Korad but you didn't even know that the B&K was a programmable dummy load!

author: GiskardReventlov
author_rank: Frequent Contributor
timestamp: February 01, 2014, 01:21:34 am
content: Quote from: pomonabill221 on February 01, 2014, 12:00:44 amFirst I think you should refrain from name calling it makes you look bad and it makes it look like you want to avoid discussing the reality.You're throwing brand names around and you seem to be personally offended by completely deserved criticism. Do you have a stake in Korad?As for wishing luck, I wouldn't pay $5 for that, it's a waste of my time. You need to understand that crap is crap no matter what the price.And I never saw him do any remote programming with it, we don't know if it works.QuoteAgain trying to deflect the real issue. Explain how or why that's relevant to discernment of that Korad crap.And that issue is that people should either find a good used supply for similar price point or save up some more and get good quality that's reliable, that has sound and logical thought behind it and that's safe to use with confidence.I watched the teardown, like I said Dave was really generous.Here's a previous quote which sums it up well:Quote from: hans on July 18, 2012, 08:28:44 amWell said Hans.

author: pomonabill221
author_rank: Frequent Contributor
timestamp: February 01, 2014, 01:33:58 am
content: You have your opinion... we all have ours...Whatever blows your skirt up!

author: Bored@Work
author_rank: Super Contributor
timestamp: February 01, 2014, 07:13:20 am
content: @GiskardReventlovYou are running in the classic problem here. Those who bought it will defend their buying decision with teeth and claws. AKA choice-supportive biashttp://en.wikipedia.org/wiki/Choice-supportive_biasYou have the same here with people defending their shitty multimeters.The Korad is the Yugo of programmable power supplies. Let them drive around in their Yugos and pretend they are driving Porsche, making some va-va voom voom sound with their lips.

author: pomonabill221
author_rank: Frequent Contributor
timestamp: February 01, 2014, 07:35:10 am
content: I never said it was a porch (that is what I think of overpriced VW's).I know it is a cheapy, and not having a job right now, I have to watch what I spend.If you would like to give me a high priced power supply, do so... I won't refuse a freebie.I am NOT defending the supply... I know it has alot of problems/limitations, but for what I use it for, it fits my purpose.I could drag out my Lambda's, but they are big, take up a lot of room, and I don't need that precision for what I am doing right now.I don't know why I even responded... the complainers here are obviously just complaining about nothing... what do they have that is better?

author: GiskardReventlov
author_rank: Frequent Contributor
timestamp: February 03, 2014, 11:02:18 pm
content: Quote from: Bored@Work on February 01, 2014, 07:13:20 amI know, sometimes it's so bad though that I can't refrain. But mostly people have to realize it ain't personal. In fact it's painful to see and in some cases (e.g. PS and multimeters) there are real and significant safety issues.If calling out a heap-O-crap was just complaining Korad would never have fixed it.But it's also very entertaining to see what horrors Dave reveals. So for that we are grateful.

author: jonathanpatate
author_rank: Newbie
timestamp: February 04, 2014, 07:58:08 pm
content: Hello from France. Here this PSU can be bought under the Velleman brand with the PS3005D reference.As said before, it seems to be an upgraded version, so it bought one, and yes it is !The fan is noisy and the buzzer stay weird too.But the encoder for selecting voltage or current is now "stem" (with steps).The 7-segment displays are well aligned/positioned (no more gap between the decoration window).Some caps are Rubycon, others stays cheapo.See pictures.

author: pomonabill221
author_rank: Frequent Contributor
timestamp: February 04, 2014, 08:03:44 pm
content: That's a spittin' image of my Korad! Not surprising though EXCEPT your front panel shows a M5 where mine shows LOCK (panel lock).

author: jaxbird
author_rank: Frequent Contributor
timestamp: February 05, 2014, 02:53:21 pm
content: Quote from: Bored@Work on February 01, 2014, 07:13:20 amIt works both ways.Frequently even stronger for those who spent a larger sum on a brand name, refusing to acknowledge that a cheaper product, can be adequate, perhaps even superior in some areas, and capable of performing the same duty.One thing I do find interesting, are those, having no personal experience with a specific product, feeling the need to express strong (often 2nd hand) opinions about it's qualities.

author: David_AVD
author_rank: Super Contributor
timestamp: February 05, 2014, 08:55:29 pm
content: I bought one of those Korad units. It feels somewhat nasty to use (poor action of the buttons mainly) but I guess I got what I paid for (just). I don't think I'd buy another one though.

author: Electro Fan
author_rank: Super Contributor
timestamp: February 09, 2014, 12:15:37 am
content: Everyone has their opinion but for what it's worth the KA3005P I've been using has been solid. It's easy to operate (the buttons, display, and dial work fine) and it checks out reasonably close to my DMMs (including a Fluke) and voltagestandard.com devices. For the price it's a good value.Here are some reviews from other users:http://www.amazon.com/KORAD-KA3005P-Programmable-Precision-Adjustable/product-reviews/B0085QLNFM/ref=cm_cr_pr_top_recent?ie=UTF8&showViewpoints=0&sortBy=bySubmissionDateDescending

author: 3w_049
author_rank: Newbie
timestamp: March 09, 2014, 04:00:29 am
content: Quote from: george graves on April 24, 2013, 12:15:55 amThe price has gone up significantly, hurry before it costs more than Agilent craps.

author: madires
author_rank: Super Contributor
timestamp: March 09, 2014, 03:14:49 pm
content: Just saw the Korad at a local online shop, EUR 80 for the KA3005D and EUR 100 for the KA3005P (RS232 & USB).

author: rr100
author_rank: Frequent Contributor
timestamp: March 10, 2014, 09:22:35 am
content: Can somebody outline the programming capabilities over USB/serial? I assume you can control it from PC but can you also read the values on display? Can you also log them? Any programming capabilities/API/command line/etc?

author: poorchava
author_rank: Super Contributor
timestamp: March 10, 2014, 02:31:44 pm
content: IMO programming PSU from PC is useful if you are trying to do some automated testing or stuff. I've built myself a PSU that can be connected to the PC and I find it that it's easier to just turn the knob or press 'recall from memory'. That's it.

author: rr100
author_rank: Frequent Contributor
timestamp: March 11, 2014, 06:14:04 am
content: Obviously dialing 5V for example is easier without going through the computer but I'm interested to either program it to use some specific algorithm or to log how much energy goes to something or how long it takes.I looked at some screen shots and for now it looks it has the capability to set whatever (or most of what) the front panel buttons set and also some time-based "scripting"/change of some parameters.However, I don't know for now:- if it reads at all to the computer the actual values- if you can do anything with them (like vary the voltage depending on the current, or maybe even current and time, etc)- if there are some scripting capabilities so you can read/write whatever you want to the PS.Other than that what would be a simple way to tell if you're getting the "good" version? I assume the decent shops by now should have the good one anyway but checking would be good.

author: Bored@Work
author_rank: Super Contributor
timestamp: March 11, 2014, 06:40:22 am
content: Quote from: rr100 on March 11, 2014, 06:14:04 amYou will find one of the problems these things have is you can't precision-time the settings. That is because of the programming interface, but also because of the PSU. Especially reducing the output voltage is a problem, because these things have caps at the output and their discharge rate depends on the load. The lighter the load, the slower the voltage change. What they don't have is what is called active down programming, an instrument-controlled rapid discharge path over the output cap(s).You also can not precision-time the readings. I.e. if you think of a sampling system, you have one with a lot of jitter in the sampling frequency. And this becomes even more apparent if you want to calculate things like power. This requires two separate readings I and V, which should be from the same time but are not. And each reading itself has a jitter with respect to the sampling frequency. The result is you can only measure very slow changing DUTs.

author: rr100
author_rank: Frequent Contributor
timestamp: March 11, 2014, 08:19:48 am
content: That's correct indeed, if there's any significant variation (even for what is considered low frequency, like 10Hz) the measurements might mean nothing and/or the CV (and even CC) might not answer fast enough.Speaking of that I think it would be worth having some tests and explanations from Dave on the pitfalls of power measurement when you can's assume the waveform and the phase of the voltage/current. Let me try to find if there's some thread with ideas for future videos :-)In any case for this application I don't care much of "fast change" is just some kind of glorified charger/test bank.

author: rr100
author_rank: Frequent Contributor
timestamp: March 14, 2014, 10:59:04 am
content: Ok, I think I can answer the questions myself: as somehow expected the protocol is easy enough and reasonably complete (I assume is the same as for the Velleman clone):http://sigrok.org/wiki/Velleman_PS3005D/InfoThis starts to go from "fail" to "best buy" in the "cheap" sector, at least in Europe where the cheapest 30V 5A seems to be about 70eur. And of course is not programmable, just one of the basic fine/coarse volts/amps, with only 3 digits on both A and V, without memories, without the possibility to set the current/disconnect load/etc. And of course you REALLY don't know what you get inside the box and for sure they try to skimp as well on power/expensive components.

author: rr100
author_rank: Frequent Contributor
timestamp: March 16, 2014, 11:03:05 am
content: I've got one for myself for 99 eur from reichelt.de.Not much to complain yet, except that the binding posts are now "internal" (multimeter-like) connectors. Of course, that makes them better safety-wise (they too take shrouded banana plugs) but still a bit of a bummer. Any (ebay?) recommendation for some cheap banana->binding post adapters that can take a couple amps?

author: soren
author_rank: Regular Contributor
timestamp: December 04, 2014, 10:28:18 pm
content: Reichelt had the KA3005D on sale for 55 EUR last Friday, so I bought one.I was a little concerned to see that it has the silly old M5 memory slot instead of a LOCK indicator, but despite this it seems to be a recent build.Some impressions:The power transistors are a pair of Toshiba 2SC5198's, which should be easily up to the task. I wonder what type the old ones were.The fan sounds like it is decent quality but it's quite loud because of chassis turbulence and being run unnecessarily fast. Maybe I'll just add a series resistor as the exiting air isn't too warm even when the power supply is at maximum thermal load.General soldering quality is good, but the hand-inserted components are all just thrown in rather carelessly. In my case, the overload thermistor had its leads shorted and it also wasn't really pressed up against the heat sink.The three large caps marked Rubycon may look okay in the picture, but they feel very rough to the touch and unlike real Rubycons, so I suspect that they are instead "con rubies".The 7812 on the controller board has a tall heat sink that is only attached to the regulator and doesn't even rest against the PCB. Extremely wobbly to the point where I'm a bit surprised that it didn't break off during transport.No overshoot! Discharging the output cap takes half a second with no load.Calibration is easy and works fairly well. There's some drift, but that's okay. I didn't expect this to be a precision product.Pressing the mechanical power switch to turn the power supply on causes a fairly strong burst of noise which doesn't appear if the switch is left on and the IEC cable inserted instead. Having read about previous runs of this PSU in the 120V version, which had lots of problems with the power switch, I wonder if they are still using that same weak switch in the 230V product and if it might be underspecified even there, causing arcing. It's also only a single pole switch.

author: Andreas
author_rank: Super Contributor
timestamp: December 05, 2014, 11:09:44 pm
content: Hello soren,Thanks for the teardown and the measurements.I also couldnt resist on black friday for 55 EUR.And some weeks ago the KA3005P went for 79 EUR as a computer controlled powerstage for my peltiers.I do not think that the fan is unnecessarily fast.In some special situations driving into 5A current limit from high voltage repeatedly(so that the relay switches happily) you are using up the SOA of the transistor at 25 degrees.If you have higher temperatures you will be above SOA.So I think I will order some 2SC5198 just in case....With best regardsAndreas

author: pomonabill221
author_rank: Frequent Contributor
timestamp: December 05, 2014, 11:47:12 pm
content: Has anyone been able to run the software for the KA3005P on windows 7 64 bit?If so, what was the software and version?I have not had any luck with mine... did work on win2000, but 7 is a no go.

author: rr100
author_rank: Frequent Contributor
timestamp: December 06, 2014, 09:55:59 am
content: Yes [it runs on win7-64], I'll let you know when I have access to that box, can't remember if it was Korad or Atten software.Can't remember if it was over serial or over usb/virtual port - most likely usb.BTW does the PS come with a serial cable? I can't remember and if it does I can't remember where I put it (if I ever had it) and is nagging me. Not that I don't have plenty of serial cables...

author: Andreas
author_rank: Super Contributor
timestamp: December 06, 2014, 10:30:53 am
content: Hello,I have tried the software on a Win XP system. (of course with blocked internet access).The function of the software was fine butthe XP system had unusual (unstable) behavior after installation.So I uninstalled the software. And system behaved as before.For me the software seems to be somewhat crappy or even dangerous.There is one file left after deinstallation. (KA3005P.aliases)content:ÎÒµÄµçÄÔ = "localhost"That what I do not understand:so for what in the world does a simple control programfor a power supply need a network access?With best regardsAndreasedit:Quote from: rr100 on December 06, 2014, 09:55:59 amMine came only with the (light blue) usb cable for connections.

author: george graves
author_rank: Super Contributor
timestamp: December 06, 2014, 10:33:06 am
content: Win 7 pro - no issues here. Sorry, don't have the version number since I re-installed windows. I think I downloaded it from their site.The power supply has been running great - bought two - no issues.

author: rr100
author_rank: Frequent Contributor
timestamp: December 06, 2014, 02:09:49 pm
content: Ok, my (as in the one I've found first...) software is called "KA3005P PROGRAMMABLE DC POWER SUPPLY V2.4". I really can't remember where I have it from but it was for sure linked from one of the big(ish) suppliers like digikey or something similar (somebody somehow trusted, at least in my mind...). It works on win7-64 but I did not test it for long time, the program looks fine but I wrote mine (see the quote below).If the original software is so fragile like my software as at first for sure it won't be very reliable to be run for longer time (there's some garbage coming now and then).Even if it is python and console-only mine won't work on windows without some rework, it is a tricky task (and os-dependent) to just read keys from the keyboard.Quote from: rr100 on November 25, 2014, 07:30:18 pm

author: pomonabill221
author_rank: Frequent Contributor
timestamp: December 06, 2014, 07:12:52 pm
content: Quote from: rr100 on December 06, 2014, 09:55:59 amThank you for the reply!My PS did not come with a serial, only a USB cable, but I prefer USB anyhow, so don't be nagged any more!Thanks for the info though! I will look further and try and find the SW... I could use it for a few simple things...

author: pomonabill221
author_rank: Frequent Contributor
timestamp: December 06, 2014, 07:26:51 pm
content: Quote from: Andreas on December 06, 2014, 10:30:53 amInteresting that the OS was affected! I, too, would remove the software if it affected my OS! Don't need any more problems.Strange file left behind?!?!?! I agree... why do they need internet access unless there was something in the help file, or "software upgrade"?Thanks for the info!

author: pomonabill221
author_rank: Frequent Contributor
timestamp: December 06, 2014, 07:31:06 pm
content: Quote from: george graves on December 06, 2014, 10:33:06 amhhmmm.... I'll take a look and try it again.I really only need it for a simple cycling test I want to run.. no real precision (I'm using my meters for that).Mine has been running just fine as well for at least a year also.Charging batteries, testing leds, supplying power for various testing, etc.Just remember the power turn on bump! Mine has that, but others report theirs do not....Overall, I do like the supply... it's small, fairly lightweight, and for what I want works fine.

author: pomonabill221
author_rank: Frequent Contributor
timestamp: December 06, 2014, 07:35:09 pm
content: Quote from: rr100 on December 06, 2014, 02:09:49 pmThanks for that... I'll take a look and give it a try.

author: Jan E L
author_rank: Contributor
timestamp: January 19, 2015, 11:49:42 pm
content: It’s about 2 years since the fail, and upgradeAnd people seems happy with the mod?I'm looking to buy the KA3005P. But on EBay all the pictures where you can see the data plate in the back still shows AC 220 V. And no 110/220 switchWhat’s up with that? Still old ones the Wun Hung-Lo distributors got there greedy hands on. And still offer to the public? Or just old pictures still being used by ignorant sellers?What EBay sellers are confirmed to sell the upgraded one?To be sure I kind of decided to order from a big Germany shop. That would be safe I thought?But the Technical details claims: Operating voltage: 230 V. And in the linked .PDF user manual it states: "110/230 V AC/ 50/60 Hz". But the picture of the back of the power supply says "AC 220 V".Sent them a request. But nothing heard yet and I'm soon out of time before I have to order someplace.Or something I missed? I thought the upgraded one was rated 240VAC? So whats up with the 230VAC and 220VAC with no 110/220 switch?

author: David_AVD
author_rank: Super Contributor
timestamp: January 20, 2015, 01:39:45 am
content: The push buttons have a horrible feel to them, the action is poor and you sometimes need to stab it a couple of times. The rotary encoder action is also pretty poor.Having the presets is handy though. I've never used the remote control port.

author: Jan E L
author_rank: Contributor
timestamp: January 22, 2015, 12:49:20 pm
content: Just to confirm. If the production date are 2013 and newer. It should have the hardwire update?I see that on Corad homepage (http://koradtechnology.com/en/cp-2.html) it's also rated 220vAC on the picture and are the same picture many EBay sellers use.I guess the conclusionon is that if you buy a new today it's almost certain you get a new version no matter what the picture says?

author: HighResolution
author_rank: Contributor
timestamp: January 31, 2015, 02:59:10 am
content: I received mine a few weeks ago. Haven't been able to use too much but I wanted to check if to see if there is any overshoot when the output is switched on.

author: pomonabill221
author_rank: Frequent Contributor
timestamp: January 31, 2015, 05:44:51 am
content: What is this a picture of? AC turn on? Output turn on?

author: Andreas
author_rank: Super Contributor
timestamp: January 31, 2015, 06:01:22 am
content: can only be output turn on.In default state after power on the output is always off.More interesting would be the following behaviour:- switching off mains by drawing / switching the AC-Line (without using the switch of the supply).- intermittend switch off / on of the AC line (so that the output just is not switched off automatically).All with low output voltage (5V / 3.3V) and low load (a few mA).with best regardsAndreas

author: HighResolution
author_rank: Contributor
timestamp: January 31, 2015, 06:19:13 am
content: Quote from: Andreas on January 31, 2015, 06:01:22 amYes it was output turn on.Here are some captures of intermittent switching on/off (output set at 3.3V and 10mA):

author: Andreas
author_rank: Super Contributor
timestamp: January 31, 2015, 11:05:21 am
content: Hello,time scale is much too fast (I do not think that you are able to switch in less than 10 us.And I do also not see any 3,3 V. Did you do AC-coupling?The sub 1us (low energy) spikes are EMI from contact bouncing which is induced most probably as common mode interference into the scope.With best regardsAndreas

author: Andreas
author_rank: Super Contributor
timestamp: January 31, 2015, 11:23:20 am
content: Just a hint:If I do that with my analog scope with around 12 mA load at 5V/0.5A setpoint. I Can see sometimes (with 10 or 20 ms/div) voltages going up to around 6 or 7V DC peak with a slow decay lasting several 10 ms.Those peaks might have enough energy to kill sensitive cirquits if you rely on the power supply as low voltage regulator.Unfortunately I can do no screen shot.With best regardsAndreas

author: george graves
author_rank: Super Contributor
timestamp: February 05, 2015, 12:42:37 pm
content: Quote from: Jan E L on January 22, 2015, 12:49:20 pmYes. Anything in 2015 should have the fix - that was a small batch.I've have two that I abuse often. No issues. The fans are annoying, so I'm going to make a video on the difference on them and a off-the-shelf PC fan.

author: PeterFW
author_rank: Frequent Contributor
timestamp: February 05, 2015, 01:19:11 pm
content: Hello Folks!I bought mine early this year from a german vendor and noticed something.It looks different from the ones i saw on the web, the posts are missing, it ony has sockets.But i can not remember if i had it open, i usually have a peek when i buy new gear.I must have had it open and checked if it was old (faulty) stock but i can not remember.Since it is still on my bench, it must be "new" inside.Greetings,Peter

author: rr100
author_rank: Frequent Contributor
timestamp: February 06, 2015, 08:32:40 am
content: Mentioned the same about the binding posts. Didn't like it much but it makes the unit much less vulnerable if transported. Also makes it straightforward to connect shrouded "banana" connectors.

author: george graves
author_rank: Super Contributor
timestamp: February 07, 2015, 03:38:26 am
content: I like the change to the sockets. The two I bought right after they did the fix on them are still running strong. No issues beside the sickly beeping tone used, and the fan noise at high amps.Also PeterFW, your front panel is different. You have M5 where other units have "LOCK"

author: GoneTomorrow
author_rank: Regular Contributor
timestamp: April 03, 2015, 09:09:21 am
content: Just received my Tenma 72-10480, which is basically a rebranded Korad, though interestingly only 3A and not 5A. It still has the binding posts rather than sockets.Naturally I immediately performed a teardown, and found the construction unsurprisingly identical to the Korad. Interestingly though, all the caps, at least on the output side, were from what I could tell genuine Rubycon caps. 105°C jobs too, which seems to be a step up from the "wan hung lo" caps that were in the Korad, assuming they ARE genuine.Anyway, I caned the thing on my redneck load tester (10 ohms worth of nichrome wire in a bucket of water) over a couple od fays and it hasn't complained yet, so that's not too bad.One issue I did have initially was a rattly fan. This initially sounded like bad bearings, but upon further investigation ended up being the fan control being very coarse in whatever it does. There must have been some very sharp edges in there, which were causing a mechanical and then audible movement in the fan. Bodging on a 33uF electro across the fan smoothed it out and now the fan no longer makes any nasty-bearing noises.All in all, reasonably happy with the unit so far, but of course the real test will be time.

author: bitwelder
author_rank: Super Contributor
timestamp: May 03, 2015, 08:47:27 am
content: Quote from: george graves on February 07, 2015, 03:38:26 amThat's something I've noticed as well. Apparently the majority of photos of KA3005P (or their rebadged versions) I can see on the market have the M5 LED on the front panel (and are probably 220V only), but some of the units for sale in US (e.g. those from SRA Soldering) seems to have the LOCK LED instead, and apparently universal 110V/220V input.Is that version with the LOCK only made for a specific reseller? E.g. I couldn't find a clear source for it on aliexpress.

author: torch
author_rank: Frequent Contributor
timestamp: August 03, 2015, 06:50:54 pm
content: I came across this Korad recently and headed to EEVblog to see what people thought of it, only to find this thread. It seems like, with the problems fixed, this might be a decent cheap PS for a hobbyist like me. Certainly the post-fix videos show it will handle some abuse.One question: whatever happened to Triosmartcal, the distributor that stepped up to the plate and stood behind their product? The links in this thread all lead to some blog page now. Did they go belly up?Second question: has anyone looked at this new triple supply? :http://www.sra-solder.com/korad-ka3305d-precision-variable-adjustable-30v-5a-dc-triple-linear-power-supply-digital-regulated-lab-gradeI'm wondering if it's two KA3005's stuffed into one case, with all the appropriate upgrades or if it's a completely new animal, potentially with all new problems.

author: David_AVD
author_rank: Super Contributor
timestamp: August 03, 2015, 09:29:16 pm
content: Quote from: torch on August 03, 2015, 06:50:54 pmThere seems to have been a slight change in name and theirweb site is here.

author: coromonadalix
author_rank: Super Contributor
timestamp: August 14, 2015, 03:39:55 am
content: Thats why i don't use any variable switch mode psu, they sometimes badly support inductive or capacitive loads, i had one die in front of me with an solenoid with an 1n4007 protection diode ... ?Sometimes the reaction/feedback speed is slow ... bad design, bad implementation etc ...Since i use linear "old" fashioned psu's, like Kepco, Hp/Agilent, I never had any problems after that.The best switched modes psu's i've tested, where from Xantrex. Oh! man many times i have tried to kill them, pushed them to their limits. Rock solid in every aspect, but $$$.That's why i love teardowns, we can see the inside guts

author: torch
author_rank: Frequent Contributor
timestamp: August 14, 2015, 10:51:24 am
content: Well I pulled the trigger on the triple version (ka3305P). I guess somebody's gotta be first. I'll take pictures when I get it open...

author: Jetiman
author_rank: Contributor
timestamp: May 04, 2016, 06:33:42 pm
content: How can I see if this is the new version or not?Will buy me this.http://www.pollin.de/shop/dt/ODE0ODQ2OTk-/Stromversorgung/Netzgeraete/Regelbare_Netzgeraete/Programmierbares_Netzgeraet_mit_USB_Interface_KORAD_KA3005P_30_V_5_A.html

author: PeterFW
author_rank: Frequent Contributor
timestamp: May 04, 2016, 06:38:49 pm
content: Quote from: Jetiman on May 04, 2016, 06:33:42 pmMail them and ask or just order it.If you do not like it, send it back.That costs nothing besides the hassle to carry that thing back to the post office.From the picture it seems to be a old unit, but maybe it is not up to date... it is pollin after all.

author: Jetiman
author_rank: Contributor
timestamp: May 04, 2016, 06:56:50 pm
content: Have it ordered, but I can see whether new or not?Comes in 2 days (Germany holiday tomorrow)

author: ProBang2
author_rank: Frequent Contributor
timestamp: May 04, 2016, 06:58:25 pm
content: Quote from: Jetiman on May 04, 2016, 06:33:42 pmDefine "old" and "new" version.If the "old" version means the device that failed in Dave´s test and the "new" version is the device with the changed board (3 big elcos), then is this the "new" version.Sure?Sure. Very sure.You can open it and check yourself without any problem. There is no "warranty void" sticker.

author: Jetiman
author_rank: Contributor
timestamp: May 04, 2016, 07:05:02 pm
content: Quote from: ProBang2 on May 04, 2016, 06:58:25 pmLeft = NewRight = oldCorrect?

author: ProBang2
author_rank: Frequent Contributor
timestamp: May 04, 2016, 07:11:21 pm
content: Correct!

author: ProBang2
author_rank: Frequent Contributor
timestamp: May 04, 2016, 07:17:19 pm
content: Quote from: coromonadalix on August 14, 2015, 03:39:55 amBTW: Just found this in another thread:Quote from: macboy on May 02, 2016, 01:17:31 pmShit happens... Everywhere.

author: Jetiman
author_rank: Contributor
timestamp: May 11, 2016, 10:40:54 am
content: PollinNew or old?Looks like mix of------------------------

author: ProBang2
author_rank: Frequent Contributor
timestamp: May 11, 2016, 01:25:39 pm
content: Middle.This is the first version after the failing issue.(On the power-transistor-board one big cap, but different designed pcb. Compare the placementof the connectors in this video:https://youtu.be/_HrvuHSywms?t=1m16s.)After this version they had changed to three caps instead of one big cap. Perhaps that is cheaper...From where Pollin got this quite old version?I don´t know, really...(I bought my KA3005P, roughly one year ago, from Pollin too. I got the newer version with three caps.)

author: Jetiman
author_rank: Contributor
timestamp: May 11, 2016, 03:14:17 pm
content: hmmmSo my is Middle old and new?So return and new order? Or keep?

author: ProBang2
author_rank: Frequent Contributor
timestamp: May 11, 2016, 04:40:24 pm
content: There is no real reason. It is nothing inherent wrong with your version.The behavior, technical data and UI are not different at all.But I can understand your wish, to get the newer version.

author: MSM
author_rank: Newbie
timestamp: May 11, 2016, 06:52:18 pm
content: Quote from: ProBang2 on May 11, 2016, 01:25:39 pmSomething really fishy is going on here! I asked Pollin about the production date of these PSUs. They said they don't know!! Also, they've listed the KA3005P for 88+4.95€ on ebay and their own website, but 156.25€ on Amazon.de!!

author: Barny
author_rank: Frequent Contributor
timestamp: May 11, 2016, 08:15:11 pm
content: Pollin is knewn as "Resteverwerter" (remnants seller).They buy their parts from closing shops / companies, overproduction, stock-clearance,....I'ts no good idea to buy parts with "expire date" like bateries, elcos,... at Pollin.ItsAnd that shops sell their parts at n higher price at Amazon should be well knewn.(Amazon-fees,...)

author: Jetiman
author_rank: Contributor
timestamp: May 15, 2016, 03:58:50 pm
content: Do I understand correctly, version is not the latest, but it does not have the errors of version 1?Then I could keep the So?

author: ProBang2
author_rank: Frequent Contributor
timestamp: May 15, 2016, 05:59:03 pm
content: Correct.

author: snovotill
author_rank: Newbie
timestamp: November 05, 2016, 11:30:07 pm
content: The original part numbers and identifying marks have been obliterated from the tops of the two microprocessors on the internal circuit boards. That is because THIS power supply hides a very special secret. The main MCU is actually a Nuvoton/Tang M054LAN or M054LDN part which contains a 32-bit Arm Cortex-M0 core. It is clocked by a 12MHz crystal but has an internal 4x muliplier so it actually runs at a very fast 48MHz. Why you ask? Because THIS power supply performs voltage and current regulation in software via DSP techniques. This is the reason why there are so few analog components and circuit boards inside THIS power supply as compared to any other. The second CPU, located on the USB/RS232 communication board of "-P" suffixed units only, is a Nuvoton/Tang NUC120LD1BN part and it is responsible for handling USB communications with your PC via firmware emulation. These power supplies have been on the market for several years now and it is claimed by various sources that the circuitry and firmware has gone through 3 very beneficial revisions and that the power supplies can now be considered to be fairly finely-tuned and stable machines. After reading several reviews in English, Polish and Chinese to confirm this (thank you Google Translate!), I eliminated all other competitors in this price-range and purchased one of these KA3005P's on AliExpress today, for less than I'd pay on TaoBao+DHL =) It is my hope that the hardware watchdog in the main MCU is correctly configured by the current rev 1.3 or higher firmware, and that the elegant simplicity achieved by eliminating unnecessary analog circuitry through the use of Digital Signal Processing techniques will provide both reliability and performance. Those of you who wish to check the firmware revision of your power supply via USB or Serial port can simply set 9600,8,N,1 and issue the following command without any EOL or CR characters, then see an instant ASCII response: *IDN?

author: Svuppe
author_rank: Regular Contributor
timestamp: November 06, 2016, 09:28:47 am
content: Quote from: snovotill on November 05, 2016, 11:30:07 pmSorry, but I don't believe that is correct.The processor controls two D/A converters (made by R2R ladders). One for voltage and one for current limiter. These two are set ONLY when changing the settings from the front panel. The rest happens in the analog circuitry (consisting of 6 opamps and a handful of passives).The overvoltage protection is most likely a software thing, but the the processor is not involved in the regulation loop during normal operation.

author: cowana
author_rank: Frequent Contributor
timestamp: November 06, 2016, 11:17:58 am
content: Completely agree with Svuppe.You only have to trace out the schematic to see this is not the case - there are three dual TL082 opamps (U5, U6, U7) which run the control loops for CV, CC and switching between the two.Not only does it seem unlikely the DSP is running the control loops - but that isn't physically possible, regardless of what software is running! Are you possibly talking about a different bench PSU?

author: Lockon Stratos
author_rank: Regular Contributor
timestamp: November 12, 2016, 07:11:37 pm
content: Greetings.I just have a quick question, with the fix Dave presented in the followup video is it safe to buy this thing? (A little bit of noise or overshoot wont matter in my case, it wont power anything "sensitive".) And what is the difference between the KA3005D and KA3005P?Thanks in advance for the help.

author: Andreas
author_rank: Super Contributor
timestamp: November 12, 2016, 11:00:08 pm
content: Hello,I have 2 KA3005P (with USB/RS232) and 2 KA3005D (without PC interface).Most time I use them in the 0.5-2A range.Large overshoot is only possible if you switch off/on the mains AC very fast.(otherwise the output is switched off on power on).Normal overshoot is around 0.4-0.5V with light loading.Largest issue are the loud fans.One of them I will have to replace in near future.(has already large vibrations on start up).With best regardsAndreas

author: Lockon Stratos
author_rank: Regular Contributor
timestamp: November 14, 2016, 01:51:45 pm
content: Quote from: Andreas on November 12, 2016, 11:00:08 pmThanks. That much overshoot wont pose much problem in my use-case. (And i think i will buy the one with the USB interface.)

author: marcone
author_rank: Contributor
timestamp: June 04, 2017, 09:24:50 am
content: Opened my KA3005D today to troubleshoot missing output voltage when outut is enabled, connector going to the output terminals had become loose. Too bad they did not glue down all connectors because otherwise construction seems very tidy for a 60 Euro power supply.Mine is the latest revision with the recessed binding posts; snapped a picture of the control board, there is actually a finned heatsink fitted. Power transistors are 2x 2SD1047 and gone are the fake Nichicons. Think I'm going to but the 10A version as well at some point, should make up for a good battery charger.

author: almamater
author_rank: Regular Contributor
timestamp: July 20, 2017, 06:40:17 am
content: Hello everyone, i bought my KoradKA3005D, received it yesterday.This is the Old version ?I think it's the Old (due the the one Big Cap and the connectors layout).. i bought from reichelt online store. If its old, what should i do?!

author: Andreas
author_rank: Super Contributor
timestamp: July 21, 2017, 07:34:36 pm
content: Hello,They seem to change the boards on every delivery lot.At least your supply has a reasonable heat sink against the thin plate with bent fingers.Afaik the new design is made with MJL 3281A transistors.with best regardsAndreas

author: LastManStanding
author_rank: Newbie
timestamp: August 13, 2017, 01:53:12 pm
content: Hi Almamater.You have the latest version - here they have omitted the terminals on the front. No way to attach wires, very annoying...My device also has no terminals. I've not noticed that at the sellers website, so i'm thinking it over to hold this device or send it back.Additional to that the fan rattles at idle.

author: GoneTomorrow
author_rank: Regular Contributor
timestamp: September 01, 2017, 02:06:43 am
content: Quote from: LastManStanding on August 13, 2017, 01:53:12 pmPut a 50uF electro capacitor across the fan, it's caused by a really coarse PWM. Smoothing with a cap stops the rattling.

author: jameson
author_rank: Newbie
timestamp: November 05, 2017, 04:16:28 pm
content: Hello! I have the same version of Korad as described byAlmamater. Voltage when output is off is 10 mV. The minimum value that was obtained after calibrating is 2 mV. Is it normal? What is the voltage when ouput is off on your power supplies?

author: Andreas
author_rank: Super Contributor
timestamp: November 05, 2017, 04:46:05 pm
content: Hello,what do you expect?Each power transistor has leakage currents in the order of some 100uA or even mA.A 30V/5A power supply is neither intended for 2mA LEDs nor 1.5 V logic supplies.Would be the same if you use a 20 pound sledge hammer for a drawing pin.Here "output off" means 4.7 mV or 12.9 mA leakage current.Zero voltage, output on = 9.5 mV or 26 mAAccuracy spec is 0.5% (of 30V) + 20 mV which means up to 170 mV total error.similarly current 0.5% (of 5A) + 10 mA which means up to 35mA current error.So your device is well within spec.With best regardsAndreas

author: jameson
author_rank: Newbie
timestamp: November 05, 2017, 06:41:35 pm
content: About the one I thought, but expect that the leakage current will be less. I have not found out what it is transistors are in my Korad.In any case thank you for a comprehensive reply.

author: Decoman
author_rank: Regular Contributor
timestamp: November 28, 2017, 05:18:06 pm
content: Did anyone ever figure out how to use the over volt and over current protection feature, and how it works?

author: janoc
author_rank: Super Contributor
timestamp: November 28, 2017, 07:23:33 pm
content: Quote from: Decoman on November 28, 2017, 05:18:06 pmI believe the original Dave's review video shows both. The OCP protection will shut the output off when you exceed a preset current instead of going into constant current mode.The OVP protection will do the same if the output voltage exceeds the preset limit. Now this I didn't play with, not sure whether it protects against user's stupidity (sending 12V into a 3.3V circuit) or whether it can handle overvoltage at the output from an external source too.

author: Decoman
author_rank: Regular Contributor
timestamp: November 28, 2017, 07:49:10 pm
content: My impression from the video was that he did not know how to actually set the over volt and over current protection value.Does anyone know? I'd like to know as I might perhaps want to use this unit.

author: janoc
author_rank: Super Contributor
timestamp: November 28, 2017, 07:56:07 pm
content: Quote from: Decoman on November 28, 2017, 07:49:10 pmOn mine you set the max current as normal and then you press the OCP button. Now when you short the output the supply will turn off the output with a beep instead of going into a constant current mode.The OVP mode is not settable from what I can see - it likely only protects against external overvoltage on the output when you turn it on.

author: Decoman
author_rank: Regular Contributor
timestamp: November 28, 2017, 08:03:15 pm
content: In that case, I would think that one would want to have OVP (over volt protection) feature enabled, always, which seems a little odd to me, knowing very little about electronics.I can't help but wonder that the feature for the OVP would seem odd in that respect.

author: janoc
author_rank: Super Contributor
timestamp: November 29, 2017, 10:30:43 am
content: Quote from: Decoman on November 28, 2017, 08:03:15 pmThe OVP protection (if it does what I think it does) only really protects the power supply by disconnecting it from the load should it detect an overvoltage condition. Which is not a very common situation - how often do you have two supplies powering the same power rail? And in such case your DUT would get fried regardless of OVP being on or off in such case because it would keep getting powered from the other supply.The other theoretical situation is that it could kick in should the voltage regulation in the supply fail (like in the original Dave's video) - however, in that case all bets are off and it is very likely that the protection circuitry itself would get fried as well.Having this constantly on would be likely annoying, especially if you are working with inductive loads that could kick up some voltage spikes on the power rails - it would keep triggering the protection and shutting the supply off.I have personally not found any use for the OVP mode. The overcurrent protection is much more useful, even though I am mostly keeping the supply in the default configuration where it goes into a constant current mode - you don't have to constantly reset the supply after even in a brief short circuit or overload.

author: glarsson
author_rank: Frequent Contributor
timestamp: November 29, 2017, 10:58:20 am
content: Quote from: janoc on November 29, 2017, 10:30:43 amWhen you use the lab PSU to charge a battery. Turning off the PSU in this setup is destructive to many PSU output stages.

author: janoc
author_rank: Super Contributor
timestamp: November 29, 2017, 11:09:41 am
content: Quote from: glarsson on November 29, 2017, 10:58:20 amIn that case an overvoltage protection won't help - the battery voltage is never going to be higher than the voltage at the output cap of the supply. So if you turn the output off and want to turn it back on, it will not get triggered (the output voltage of the PSU is higher than the battery voltage).If you mean turning the supply completely off with a battery connected - then the OVP system is obviously useless as it has no power. Also we are talking about a lab supply, something that is designed to handle all sorts of abuse, so I would expect it to have some protection diodes in to prevent this sort of situation.

author: Decoman
author_rank: Regular Contributor
timestamp: November 29, 2017, 09:41:59 pm
content: Having read Andreas' post above regarding specced output errors, and not knowing much about electronics, I want to ask:Would this powersupply be ok for powering one or more LED's, which run with 2-3V and 10, 15 or 20 mA? Or would this powersupply be too crude?Looking at youtube videos I think I've learned that LED's don't like voltage overshoots. As the LED's will easily burn out, when being over powered.Also, the unit is specced for 110-220V, but would it be ok, or a bad idea to have it run on 230V? (Norway). My impression is that this power supply can run 220V and the specced + 10% would cover 230V, but if there might be issues, I have no idea myself.

author: janoc
author_rank: Super Contributor
timestamp: November 30, 2017, 04:59:14 pm
content: Quote from: Decoman on November 29, 2017, 09:41:59 pmYou can power LEDs from it in constant current mode (set the current limit to e.g. 10mA) but do not turn the supply and off with the LED connected. Otherwise you are risking that the diode dies before the output voltage stabilizes if there is any overshoot. It is a decent supply for the price but certainly no high end, so some overshoots and what not are to be expected. Better safe than sorry.Re 230V - that should be safe, the 220V mains voltage comes with +10%/-6% tolerance, so anything meant to be used with it has to be able to deal with at least 242V. So no worries there.

author: Andreas
author_rank: Super Contributor
timestamp: December 01, 2017, 09:42:12 am
content: Hello,10-20mA LED?I wouldn do that without a series resistor for the LED (on any power supply which can deliver more than 50 mA).Especially as the KORAD has a 330uF output capacitor.What happens if you connect a 100R resistor (instead of the LED) to the output when the voltage is set to 15V and current limit is set to 20mA can be seen in the screen shots. (voltage measured across the 100R resistor).Peak current reaches nearly 150 mA and current declines with a time constant (30ms) corresponding to the 330uF capacitor.So if you dont care your LED (50mA max peak) may be destroyed here.Steady state current is 22.8mA (measured with DMM). But this may vary dependent on device and room temperature.It will be better if you use the off/on button on the KA3005.(The cheaper KD3005 devices dont have it).On my device I have seen no overshoot in this setting.with best regardsAndreasAndreas

author: janoc
author_rank: Super Contributor
timestamp: December 01, 2017, 10:24:50 pm
content: Quote from: Andreas on December 01, 2017, 09:42:12 amI have obviously meant using the output on/off button on the Korad or disconnecting the leads, not toggling the main power switch. That would be a terrible idea, indeed - both because of the capacitor charging currents and the potential transients when turning the supply on and off.Are there variants that don't have this button? I have only seen variants that don't have the 5th preset LED (that you get to by selecting 4th preset and then turning the knob) and have some other function instead of it.

author: Decoman
author_rank: Regular Contributor
timestamp: December 10, 2017, 07:38:52 pm
content: I ordered the KA3005D variant (without usb), and I thought some might find it interesting if I opened it up (without killing myself ofc) and shares some photos of its innards. I am anxious to learn if there might be any loose items inside.The one I ordered seems to maybe have the four memory buttons, and hopefully this is a newer variant. The unit I ordered should arrive within a week I would think.I will definitely feel more comfortable knowing what the insides looks like on this unit of mine, before using it, presumably I am receiving a fairly newly manufactured unit. I ordered mine from sra-stores on ebay, if it is any good, I don't know yet. Ofc, I am not qualified to judge, but I suppose there are some basic things i can check.

author: Mr. Scram
author_rank: Super Contributor
timestamp: December 11, 2017, 01:09:41 am
content: I opened up my dual rail variant and was surprised to find one massive transformer, instead of the two discrete units tied together I expected. It makes sense to do it this way, obviously, but I understood the units to be constructed differently.

author: Fkossy
author_rank: Newbie
timestamp: February 21, 2018, 11:58:09 am
content: Hi all,In my country supply voltage 220V, typically around 210V-230V.My power supply is meant to work with 220V, but his transformer hums and heats up at even no load.This is my problem, or typical quality for this power supply?

author: ProBang2
author_rank: Frequent Contributor
timestamp: February 24, 2018, 02:17:34 am
content: Hello.My KA3005 is declared for 220V mains voltage, too.Actual mains voltage: 235.2V (measured right now).When powered on, then there is for less than asecond a strange sound from the transformer. Afterthat: There is no hum. The sole noise is the air ventilation.And the unit does not heat up. Even not with a small load.It seems, there is a problem with your specific device.Sorry.

author: chaoticmayhem65
author_rank: Contributor
timestamp: April 07, 2018, 06:56:20 pm
content: Does anyone have a link to the control software other than v2.6 that is available on the SRA website? Possibly v2.4?

author: HoracioDos
author_rank: Frequent Contributor
timestamp: April 07, 2018, 07:17:07 pm
content: Quote from: chaoticmayhem65 on April 07, 2018, 06:56:20 pmBy chance I posted what you might need a few minutes ago.https://www.eevblog.com/forum/testgear/korad-ka3005p-software-update/

author: chaoticmayhem65
author_rank: Contributor
timestamp: April 07, 2018, 10:46:37 pm
content: Quote from: HoracioDos on April 07, 2018, 07:17:07 pmWell thanks for the link, but unfortunately it still has the problems I was having with the other software. The graphs are way too small and the program won't let you maximize the window to full screen. I've tried v2.5 and the window is physically bigger, along with larger graphs, but the program still wont let you maximize the window to view it in full screen.

author: HoracioDos
author_rank: Frequent Contributor
timestamp: April 07, 2018, 11:12:18 pm
content: Quote from: chaoticmayhem65 on April 07, 2018, 10:46:37 pmI think that I have V2.3 somewhere. I'll let you know if I can find it. Meanwhile you might try these:http://www.sprut.de/electronic/soft/korad/ka3005p.ziphttps://github.com/crapp/labpowerqt/releases/download/v0.1.3/labpowerqt_setup_0.1.3_x86_amd64.exe

author: bitwelder
author_rank: Super Contributor
timestamp: April 08, 2018, 07:02:56 am
content: Is it possible to find anywhere only the USB control board for the KA3005P ?Just wondering if it would be possible to upgrade a D version into a P version

author: ProBang2
author_rank: Frequent Contributor
timestamp: April 08, 2018, 08:29:33 am
content: If I remember correct: That was tried already.The firmwares of the PSU with and without USB connection are different and the Korad KA xxxxDdoes not support the interface.

author: chaoticmayhem65
author_rank: Contributor
timestamp: April 08, 2018, 04:39:20 pm
content: Quote from: HoracioDos on April 07, 2018, 11:12:18 pmSo does your version not let you maximize the window as well?

author: HoracioDos
author_rank: Frequent Contributor
timestamp: April 08, 2018, 08:55:44 pm
content: Quote from: chaoticmayhem65 on April 08, 2018, 04:39:20 pmI don't remember but you can check it. I sent you a PM with download links.I hope this could help.

author: chaoticmayhem65
author_rank: Contributor
timestamp: April 09, 2018, 12:52:14 am
content: Why is it that none of these Korad software revisions will let you maximize the window to fullscreen? The voltage and current graphs are absolutely pointless if they are too small to see without the ability to make them bigger. The software would be much more useful if you could just view it in fullscreen just like every other program out there under the sun.........but yet you can't. And why is this software so hard to find? It's not even available on the official Korad website! And to top it off, the software disc that came with my unit was blank. Good thing SRA had software download links posted on their website.

author: Mr. Scram
author_rank: Super Contributor
timestamp: April 09, 2018, 01:05:37 am
content: Quote from: chaoticmayhem65 on April 09, 2018, 12:52:14 amCan you post a screenshot? That way we can maybe help.

author: HoracioDos
author_rank: Frequent Contributor
timestamp: April 09, 2018, 11:21:48 am
content: Hello!I forgot to mention that you could write your own program to generate graphs without dealing with interface problems if you use sigrok. It's a command line program to control many lab devices. There is a windows version. You can get a text output with a simple script that you could read and plot if you code a little bit. These are some examples for linux.sigrok-cli --driver=korad-kaxxxxp:conn=/dev/ttyACM0 --scan (Scan device)sigrok-cli --driver=korad-kaxxxxp:conn=/dev/ttyACM0 --show (Show device options)sigrok-cli --driver=korad-kaxxxxp:conn=/dev/ttyACM0 --config "voltage_target=3.3" --set (Set output voltage)sigrok-cli --driver=korad-kaxxxxp:conn=/dev/ttyACM0 --config "enabled=on" --set (Enable output)sigrok-cli --driver=korad-kaxxxxp:conn=/dev/ttyACM0 --continuous (Get countinuous readings)sigrok-cli --driver=korad-kaxxxxp:conn=/dev/ttyACM0 --continuous -o readings.log -O csv (Get readlings to a text file)I hope this can help to think other options if software doesn't meet your spectations.

author: HoracioDos
author_rank: Frequent Contributor
timestamp: April 09, 2018, 12:58:12 pm
content: HiI also forgot to mention. Did you try to maximize the window using a shortcut/keyboard. Windows key + up?

author: chaoticmayhem65
author_rank: Contributor
timestamp: April 10, 2018, 09:08:19 pm
content: Quote from: HoracioDos on April 09, 2018, 12:58:12 pmYes I did. It did nothing. The maximize tab was also greyed out and you could not resize the window whatsoever.And thank you so much for uploading those different versions of the software for me. They solved my problem. You gave me v2.4 and v2.5. And they both let me view the program fullscreen. I decided to go with v2.5 since v2.4's current graph was not functional. Weird how out of the many versions I tested out, only your two let you view the program full screen. And even stranger yet, your version of v2.5 is somehow different than the version of v2.5 i was using. Yours lets me maximize, mine would not.

author: HoracioDos
author_rank: Frequent Contributor
timestamp: April 10, 2018, 10:05:19 pm
content: Quote from: chaoticmayhem65 on April 10, 2018, 09:08:19 pmPerhaps I'm wrong but I guess that Korad gave license to third ones to build and sell their PSUs. May be that's why there are so many software versions and there are small changes in hardware. This issue made me want to play a little bit with sigrok and gnuplot.Any way, I'm glad that worked and your problem was solved.

author: lt_cdr_data
author_rank: Newbie
timestamp: May 22, 2018, 01:55:09 pm
content: Hi, the light blue resistor R3 is blown on my device (mounted on the upper edge of the board, close to the fan connector) could anybody tell me it's value, so i could replace it.﻿ TIA

author: wasyoungonce
author_rank: Frequent Contributor
timestamp: May 24, 2018, 06:50:53 am
content: Well blow me down. Show on stargazing on ABC in Australia with Brian Cox, Australian physicist Allan Duffy etc.They showed a clip of them st radio telescope Parks I think i electronics processing room and ....wait for it...are you ready.... looks to be a Korad PSU on top of station supplying pwr to some station part.I think it’s the ubiquitous 5 memory version in question here... here’s the money shot:HahahaSent from my iPhone using Tapatalk

author: Peter63
author_rank: Contributor
timestamp: June 17, 2018, 11:32:53 am
content: Quote from: lt_cdr_data on May 22, 2018, 01:55:09 pmI have a Velleman PS3005D 30V 5A unit. Have you replace the R3 resistor? Can check R3 resistor in my unitPeter

author: helltron
author_rank: Newbie
timestamp: April 03, 2019, 05:22:40 am
content: Hey guys, i hope you can help me with an strange issue i have with my KORAD KA3005D. (board label KR1025) It stops showing the current on the lower 7seg in ON mode. I've checked the schematics, measured the voltage at Anode of D5 and it reflects the current flow in millivolts (e.g. 80 mA gives 80 mV), but the display stays at 0.000 :-(Maybe the AD input broke, but how can i replace the uC ? It is labeled "KORAD01" but i am pretty shure it is just an Atmega8 or such. Also i would need the firmware to flash a new one.Any hints?

author: iMo
author_rank: Super Contributor
timestamp: April 03, 2019, 11:21:25 am
content: Could we see the schematics?

author: helltron
author_rank: Newbie
timestamp: April 03, 2019, 02:32:52 pm
content: Oh, yes, of course :-)

author: iMo
author_rank: Super Contributor
timestamp: April 03, 2019, 06:47:58 pm
content: None schematics in your .pdf..

author: helltron
author_rank: Newbie
timestamp: April 04, 2019, 05:09:06 am
content: Sorry, here they are.I also managed to get may device back to function again. A recalibration healed it!

author: lewiss66
author_rank: Newbie
timestamp: April 30, 2019, 05:23:31 am
content: Hello, I just received my Korad KA3005P PSU and after some teardown I realized that the USB COM board looks like an old version with no opto couplers:But on the other hand the pwr board looks rather new:Any idea if the PSU they sent me is a new model or a mix of old and new?BTW I checked the control of the PSU with a program software found on the net and it works. The OEM software I got in the CD is in true Chinese...Though this USB com board doesn't feels like it is a protected one. How can I check if I can trust it? ThanksA large view of it:

author: pete1zed
author_rank: Contributor
timestamp: May 16, 2019, 07:14:07 am
content: Here is the manual for the dual channel version, marked up with corrections and warnings about bugs in the user interface and behavior:https://ufile.io/drsjx09jThis applies to models:- TENMA 72-10495 (Korad KA3005D-2S): 30V-5A x 2 Channels- TENMA 72-10500 (Korad KA3003D-2S): 30V-3A x 2 Channelsand probably also- TENMA 72-10505 (Korad KA3003D-3S): 30V-3A x 2 Channels & 5V-3A x 1Important notes to avoid damage:● Do not allow power supply to sink current. Use diode when charging battery.● For sensitive circuits, see Avoiding overshoot and excessive in-rush current :○ Inside the power supply, there is a capacitor near the output terminals for stability. The current limiting and over currentprotection (OCP) cannot control current from this capacitor.○ There is some overshoot on turning a channel on.○ There is a spike when turning mains off while the channel is on.● In parallel mode, connect load to CH2 (right hand) channel. (When mains power is turned on, the power supply defaults toindependent mode, and CH1 to whatever voltage and current settings are in CH1 memory recall M1, with the load turned off.Therefore, avoiding CH1 could prevent mistakenly applying wrong settings to the load.)● OCP and OVP do not work in serial and parallel modes.● If you recall a CH2 memory in SER mode, only CH2 is updated from that memory and only CH2 turns off. At this time, CH2output terminals have up to -1.2 V (i.e. reverse polarity) on them, with a short circuit current of up to -2.8 A.This also happens when the channels are independent but you have wired them in series.● When using the power supply in SER mode, or wired in series, you may have to ensure the supply is working in CV mode toavoid instability.Important notes to avoid confusion:● There is a small negative voltage and current when the load is switched off (50mV, 100 uA)● OCP/OVP:○ CH2 OUT LED stays on after CH2 OCP/OVP trip disconnects the load.○ OCP and OVP do not work in serial and parallel modes○ CH2 OVP/OCP buttons also control CH1 OVP/OCP○ CH1 OVP/OCP buttons only control CH1 OVP/OCP○ The OCP and OVP LEDs apply to whichever channel last updated them. Pressing either the OVP or OCP button updates both theOVP and OCP LEDs with that single button push.● An OCP/OVP trip for one channel does not trip the other channel

author: Xenoamor
author_rank: Regular Contributor
timestamp: June 04, 2020, 09:24:27 am
content: Quote from: lewiss66 on April 30, 2019, 05:23:31 amAren't U3 and U4 the optocouplers there?

author: electronx
author_rank: Regular Contributor
timestamp: September 02, 2020, 07:53:21 pm
content: I bought a redesigned version of the product about 6 months ago, I see quite a lot of improvements in pcb, they have replaced some capacitors with smd capacitors. I've tried programming from the computer, vertical linear triggering can be done, even if it's not millisecond precision. They've fixed the sound problem and the fan runs quieter. Soon I will measure and share the results with a 200Mhz oscilloscope and a 5.5 digit multimeter.

author: Photolunatic
author_rank: Contributor
timestamp: November 14, 2020, 11:07:02 pm
content: Quote from: electronx on September 02, 2020, 07:53:21 pmWhere did you get it from? I am having a hard time to find one.Welectron says more than 30 days for delivery!https://www.welectron.com/Korad-KA3005P-Benchtop-Power-SupplyThere are some on Amazon US but with all fees, it comes close to £140

author: nightfire
author_rank: Frequent Contributor
timestamp: November 14, 2020, 11:55:58 pm
content: Reichelt in germany marks both D and P version as available for 106 Euros incl. sales tax for the P version.

author: Photolunatic
author_rank: Contributor
timestamp: November 25, 2020, 02:31:47 pm
content: Quote from: nightfire on November 14, 2020, 11:55:58 pmThanks.I found that Reichelt and Welectron are both selling units with safety terminals at the moment.Is it a deal-breaker for anybody else or is it just me?I was decided to get one with screw-in terminals that the majority of KA3005 had.I couldn't find a cost-effective source with shipping to the UK so eventually, I may get one with safety terminals from Welectron (pictures attached)

author: gimpo
author_rank: Contributor
timestamp: January 05, 2021, 01:07:17 pm
content: Just bought the Korad 3005D (without USB) fromReichelt-Germanyfor 89,00 EUR + delivery. I hope it is the redesigned version...Terminals are different, so it should be the "new" version. Any other detail that I could check without opening it?

author: midix
author_rank: Contributor
timestamp: June 17, 2021, 09:57:06 am
content: So, I now have a choice among these "Korad clones" by a company called RND:320-KD3005D (two knobs, no buttons)320-KA3005D (one knob, with buttons)320-KD3005P (two knobs, no buttons, with USB)velleman LABPS3005D, replaced by LABPS3005DN, (one knob, with buttons, with USB)and completely different models from UNI-T:UTP1305UTP3315TFLUTP3315TFL-II(not sure, what they have actually changed for the II version).What do you think? Which, in theory, should be a more reliable choice - the Korad clones or UNI-T?At least, we now know what to expect from these "Korads", but UNI-T models are a total unknown for now.

author: Andreas
author_rank: Super Contributor
timestamp: June 18, 2021, 06:24:28 am
content: Quote from: midix on June 17, 2021, 09:57:06 amNo: (from a "RND" datasheet)"RND is a trademark of Dätwyler Schweiz AG, Gotthardstrasse 31, 6460 Altdorf, Switzerland, info@rnd-electronics.com"I can only speak for the Korad / RND devices:I personally like them (and the RND devices have the better pole terminals instead of "security sockets")They are cheap (so dont expect too much)you have to be prepared that after 2 years you have to exchange the rotary encodersAs I usually work with "standard voltages" (5V 12V 15V 18V) programmed to the knobs or use them in automated measurements by RS232 interface I rarely use the rotary encoders.with best regardsAndreas