$200 power supply: New KORAD or used HP, Tektronix, or similar?  - Page 1
Forum section: electronics / beginners

author: MaxBishop
author_rank: Contributor
timestamp: April 07, 2024, 08:59:10 am
content: Hello. I trust your experience more than my research. I’m going to spend in the neighborhood of $200 on a power supply. I need/want dual output, up to 30v, not sure about amps. I don’t mind servicing older stuff and actually like vintage stuff that is reliable but need it to work from the start as my project has a timeline. Based on past experience would you buy two KORAD KA3005’s (or comparable) or would you purchase a used, dual output HP, Tektronix, BK or similar off of eBay. I’m new with limited knowledge so if you have other suggestions please feel free to share other possibilities. Any help is appreciated.

author: aliarifat794
author_rank: Regular Contributor
timestamp: April 07, 2024, 02:52:57 pm
content: These brands have a reputation for reliability and performance.Look for models that meet your voltage and current requirements.

author: donlisms
author_rank: Frequent Contributor
timestamp: April 07, 2024, 03:06:24 pm
content: I have bought several used Power Designs, one HP, and one Lambda supply, and had pretty good luck with all of them.The HP needed the most attention - the power switch crumbled; the smoke came when I turned it OFF! Confusing. Not a typical fail, I think. It also has old stiff wiring that needs replacing.The PD's just seem to work; I love them, and would like more, just because I like 'em, not because I need 'em!

author: coromonadalix
author_rank: Super Contributor
timestamp: April 07, 2024, 03:08:23 pm
content: I'm not impressed by Korad .... i would choose any reputable brand well before that one, and if you don't find a dual one, buy two identical models,if it's the case you'll have to fiddle, serial and parallel mode ..Some Mastech and clones had better reliability in the pastDo note, you pay cheap, you'll get cheap

author: Electro Fan
author_rank: Super Contributor
timestamp: April 08, 2024, 08:22:09 am
content: Quote from: coromonadalix on April 07, 2024, 03:08:23 pmWhat problems did you have with your Korad?

author: voltsandjolts
author_rank: Unknown
timestamp: April 08, 2024, 08:31:08 am
content: Buy your test equipment second hand, preferably broken (and repairable).You'll lose much less money that way, learn something doing repairs and likely make a small profit when you sell it on.

author: psysc0rpi0n
author_rank: Frequent Contributor
timestamp: April 08, 2024, 09:01:52 am
content: I have 2 Korad KA3005P. For what I do I cannot complain.From what I could check when I purchased them, they are accurate and the only thing that is on the cons is the confusing OCP and OVP buttons and their functions. I recently watched a video of someone trying to figure out how to deal with these 2 buttons and the guy was also quite confused!From minute 18, it starts the struggle with these functions! Other than that, I'm happey with both of them!

author: BILLPOD
author_rank: Frequent Contributor
timestamp: April 08, 2024, 12:39:50 pm
content: Quote from: psysc0rpi0n on April 08, 2024, 09:01:52 am

author: MaxBishop
author_rank: Contributor
timestamp: April 09, 2024, 05:26:30 am
content: Quote from: donlisms on April 07, 2024, 03:06:24 pmWhat PD models would you recommend for dual output and up to 30V? Also, is Power Designs and Power Designs Precision considered the same quality?

author: donlisms
author_rank: Frequent Contributor
timestamp: April 09, 2024, 10:07:35 am
content: There are several dual and triple versions, e.g. the TW4005 is a twin 40 volt 0.5 amp model. I don't have one but want one. I have a 6050, single output 60 volts or 5 amps, but not both at the same time!The Precision models, always with those nice four-digit dials, are probably about an order of magnitude more precise. Single output. Specs are 100uV noise and regulation and such; I usually see around 10uV or less, including watching the oven heater switch on and off. (Newer models used LM399.)The precision models are good enough that you start expecting them to be a reference; not to metrology standards, but sub-millivolt easily.Quality... well, I guess... the designs came out of the same brain, but for different purposes. They're all nice.All the PD's are old, no doubt. A little control cleaning might be in order; I keep thinking I should do that someday. Mine just work, except some of the meters. Which I should fix someday, but... no big deal.I should say this: the current limiting adjustment is intended as a safety net, not as a CC supply. The limit is a little vague. In those days, CC wasn't such a normal thing. As best I understand it, you want an infinitely high output impedance for CC and zero for CV, so supplies that try to do both must compromise a little somehow in their output circuitry.I suspect the HP's are similar to the PD's in most ways, including their precision versions (uhm... 6111? 6112? Others?).

author: MaxBishop
author_rank: Contributor
timestamp: April 09, 2024, 12:37:33 pm
content: Quote from: donlisms on April 09, 2024, 10:07:35 amThank you! This is helpful. They've come up in my searches. I like the old school look and assumed (but didn't know) the build quality matched the appearance. I'll include them in my list of options. Gonna have to pull the trigger within the next week or so. I appreciate your input.

author: Electro Fan
author_rank: Super Contributor
timestamp: April 09, 2024, 12:48:35 pm
content: Quote from: MaxBishop on April 07, 2024, 08:59:10 amHave you built or repaired power supplies?What other test equipment do you have?What is your project and timeline?

author: MaxBishop
author_rank: Contributor
timestamp: April 10, 2024, 05:38:31 am
content: Quote from: Electro Fan on April 09, 2024, 12:48:35 pmI haven't built any but I'm gathering parts. I have a few laptop battery packs. I'm intimidated by the thought of it. Is there a build you would recommend? This is all new to me. I don't have anyrealgearother than a couple of voltmeters and an old, currently misplaced oscilloscope that my dad used to use many years ago. My project is already late, lol. I sent a message to an eBay seller tonight on an HP 3620. We'll see what comes of it. If that doesn't pan out there are a few other brands/models I'm watching

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: April 10, 2024, 12:05:35 pm
content: About old PS, some of them have an IC that is very hard to find. This chip is the thing that blows, without the chip it is very hard to fix. I have a Lambda like this, I redesigned the control circuits for it but this is a hard thing to do. This is an old Lab Grade Supply with analog meters.I do not know if any of the more modern PS with Digital Meters have this same problem with hard to find reference chips.This is too bad because these old PS have good transformers.

author: mr ed
author_rank: Regular Contributor
timestamp: April 10, 2024, 09:25:03 pm
content: I got fed up with cheap chinese switchers and went with used hp 6236 (6v 2.5a and +/-20v 0.5a ) and 6284 (20v 3a) when the half amp wasn't enough. Get the more recent ones, not the real old ones by Harrison with the colored hp logo. The 6284 has a safety crowbar too. They can be stacked in parallel or series so in principal I can get 60 volts if needed at 0.5a. No fans.

author: Electro Fan
author_rank: Super Contributor
timestamp: April 12, 2024, 02:59:44 am
content: Quote from: MaxBishop on April 10, 2024, 05:38:31 amOKStill not sure what your project is but it sounds like you have something in mind that needs a power supply. Some people like to build a power supply, others are into refurbishing/repairing power supplies - both approaches can be good ways to learn and/or keep the budget down.Having said that, if everything is new to you then I think you might be better off starting with a few pieces of reliable and reasonably accurate pieces of test equipment. If you have a decent power supply and a decent DMM then when you measure V, I, and R you will have some confidence when your measurements and calculations agree, or some reason to relook the measurements and/or calculations if they don’t agree.It depends on how much adventure and experimenting you want to do - but if you are new to electronics and you want to learn and build stuff I’d recommend starting with a few decent tools. Along these lines, a used power supply might save some budget but for about $110 you can get a 30V 5A Korad that will be fairly accurate. Starting with a new working PS from a reliable seller is probably going to be a better experience than starting with a used PS but YMMV. A KA3005D from Amazon can be returned if it isn’t working or doesn’t meet your expectations. I’ve had one for about 10 years and it’s been rock solid; I bought a 2nd unit a couple years ago, and I gave another one as a gift to a new EE. Until you know what else you expect from a PS it’s likely all that’s needed.If you start with one Korad and you really need another PS you can buy a second unit. Sometimes it’s nice to have two of the same pieces of test equipment. You can compare measurements, you will be familiar with the UI on both, and if one is used in another location or is unavailable you have a spare.

author: MaxBishop
author_rank: Contributor
timestamp: April 12, 2024, 05:18:49 am
content: Quote from: Electro Fan on April 12, 2024, 02:59:44 amI appreciate you taking the time to provide this feedback! I agree that I should get something that is known to work and go from there. Before I came to that conclusion, I bid on an HP PS on eBay but did not get it. It was kind of the (most recent) final straw for me.My project is simple, but I lack experience and knowledge. I want to make a simple machine surveillance system. Once the initial phase is working well, I’ll add phase two and so on. I’m starting with a Raspberry Pi, some simple diffuse reflective sensors and a bit of coding to count input vs output to get a solid waste count. I didn’t know how to power the sensors, so I Googled it, and it led me here.The power supplies listed here are overkill for what I need to do but now I have the bug and, need it or not I want a capable power supply for future projects. To your point on the Korad, I agree. Yet, I haven’t pulled the trigger because I’m envious of all the cool gear I’ve seen here!As far as my project goes, I was gifted an Allen Bradley 1606-XLP yesterday. It was in a junk pile at work. It is doing what I need for now and it’s affording me time to be picky on my future power supply. The power supply was simply to bench build the system. Acquiring the Allen Bradley was a surprise that, lucky for me, will work for the completed system. The search continues.

author: Electro Fan
author_rank: Super Contributor
timestamp: April 13, 2024, 08:22:27 pm
content: Read Reply #5 and#6 in this thread:https://www.eevblog.com/forum/testgear/are-premium-scope-brands-still-justified/msg5448176/#msg5448176The thread and Reply #5 and #6 are about professional use but the concept applies at some level to enthusiast use also - if you can’t reasonably rely on measurements it can be extra confusing and time consuming.

author: MaxBishop
author_rank: Contributor
timestamp: April 13, 2024, 08:32:23 pm
content: Quote from: Electro Fan on April 13, 2024, 08:22:27 pmThank you. More data points for me to consider. There just is no simple path. Well, I guess if funds are abundant that would be a game changer.Maybe, I should be asking the experienced folks here what investment amount is reasonable.

author: Electro Fan
author_rank: Super Contributor
timestamp: April 13, 2024, 09:50:44 pm
content: It’s always good when asking questions here to give context. How much knowledge, experience, skill, budget, etc do you have to apply? What are the objectives, short term and long term? Test Equipment is like a tool - it can help a person solve problems, learn, and have a very enjoyable journey - but it can sometimes be like a drill to make rabbit holes.The question about a “reasonable investment” is a good one - but give some thought to that not just for a power supply or two, but for a bench full of test equipment that might surprising populate like rabbits. There are threads here you can find by searching that give advice on what new enthusiasts should consider with respect to various types of test equipment, tools, parts, consumables, etc.The forum members here are super helpful and will try to answer your questions but you will get the best answers when you frame the questions well with your context. Otherwise you might get a lot of enthusiastic answers from someone else’s context. Checkout a thread called “TEA”; there might be at least a couple - one short and one long. If you read thoroughly you might find, for example, some people will say you haven’t reached par on oscilloscopes until you have 19.After ~10 years of thoroughly enjoying EEVblog I’m about 15 short of par on oscilloscopes but I’ve made due with just (2) Korad power supplies. That doesn’t mean Korads are right for you - but I’m sure a person can learn a lot and get a lot done with <30 volts and <5 amps if the PS is easy to use, reliable, and accurate to a few hundredths of a volt and a few milliamperes - which the KA3005D is. It will probably be fine out of the box but there is a calibration routine you can use to dial it in with a DMM. But here you see the beginning of the rabbit hole. What if your DMM isn’t accurate?My suggestion would be start with a Korad PS and a couple decent DMMs (so you can measure voltage current at the same time), and climb in the rabbit hole.Once you see voltage and current on your two DMMs agree with the voltage and current readouts on the Korad and all four readouts agree with the calculations you made before hand for your Device Under Test you will be certified to climb in and out of the rabbit hole under your own power - just watch out for TEA symptoms.

author: Jwillis
author_rank: Super Contributor
timestamp: April 13, 2024, 09:53:45 pm
content: Mastech power supplies are now VOLTEQ.https://www.volteq.com/. The design has been around for years and are robust, reliable and very easy to repair and calibrate.

author: Electro Fan
author_rank: Super Contributor
timestamp: April 13, 2024, 10:08:33 pm
content: fwiw, I think you want a linear PS and one with a DC output on/off button, not just an AC on/off button. And then you will want to see how cleanly the output turns on and off - which will be the sound of the rabbit hole telling you maybe you need to buy an oscilloscope to see and measure the waveforms.edit: and then you can post your scope’s screen captures of the PS output on/off, at which time you will realize you might need some different probe grounding techniques and accessories to avoid ringing, etc and help you confirm your PS has relatively low ripple, and so on and so forth….

author: MaxBishop
author_rank: Contributor
timestamp: April 14, 2024, 06:05:47 am
content: Quote from: Electro Fan on April 13, 2024, 10:08:33 pmWhat in interesting coincidence. Your timing is spot-on. I've been picking through this post tonight.https://www.eevblog.com/forum/beginners/oscilloscope-training-class-(long)/Mind blown.I can see the rabbit hole ahead, lol. I don't have a good power supply or oscilloscope, that I can find, anyway. I have my dads old scope around here somewhere. Regardless, already I can't seem to settle on just one of either. I have to remind myself this is what I do, jump in with both feet, usually with a fair amount of regret later. So, all the feedback I'm getting is most welcome! So, I have a Fluke, I believe it's a 17B or similar and a Klein Tools CL210. Hopefully, that's a decent set of starter DMM's. i can't seem to settle on the vintage power supply I want to purchase so I'm good with the KORAD. Quick question on that... I'm assuming the difference between programmable vs non programmable is well worth the $24 difference. Any thoughts on that are welcome.

author: Electro Fan
author_rank: Super Contributor
timestamp: April 14, 2024, 01:05:15 pm
content: Given your questions and comments I don’t think you will regret jumping into the rabbit hole - but to get the best experience I suggest using a good ladder.The trick to getting a ladder that will enable an ee (non-degreed electrical enthusiast) to safely and enjoyably climb in and out of the rabbit hole, imo, is to get well grounded (haha) in Ohm’s Law. This means doing enough simple math to understand and reasonably predict the relationships that result from V=IR.Print the wheel and post it near your bench.https://www.formulacalculators.com/ohms-law-calculator/DC is a good place to start, then when you get to AC you can build on the foundational concepts and math learned with DC. AC will add things like RMS. Along the way you will start to recognize the concept of reactance as you distinguish impedance from simple resistance. The oscilloscope can help you visualize some of this and if it has useful math or measurement readouts the scope can help you connect the wave form insights to measurement insights. Things like Peak to Peak vs average vs RMS and 50 ohms vs 1 M ohms will start to show up over and over like markers on your rabbit hole ladder. This is a long way of saying you don’t need an expensive DMM but I’d get one with TRMS vs average RMS. When you see numbers like .707, 1.414, and 2.828 in your dreams you will know you are making progressAnd when this chart makes sense you will be another ladder rung proficiently into the rabbit hole.https://www.minicircuits.com/app/AN40-012.pdffwiw, from an early rabbit hole journey:https://www.eevblog.com/forum/testgear/fluke-17b-rms/For high voltage stuff, get a Fluke or Brymen. For low voltage stuff get one or two Aneng 8008 (save money and get good features with surprisingly good accuracy).The KA3005P adds the programmable PC interface and won’t cost much more than the KA3005D (but you might find the software a tad primitive). Both the D and P offer excellent value for the price.As for scopes, just take the elevator into the rabbit hole, get off on the Siglent floor marked HD.This advice is intended to save you time and money. Enjoy the journey, it is likely to be fascinating.edit: Maybe add one Aneng 8008 from Amazon to your Fluke and Klein collection and you are set on DMMs.

author: MaxBishop
author_rank: Contributor
timestamp: April 15, 2024, 05:12:31 pm
content: Quote from: Electro Fan on April 14, 2024, 01:05:15 pmThis is all a bit intimidating... SOOO much information! I downloaded the charts. Thank you. After looking closer at the Fluke 17b I am wondering if that is actually the model I have. If it is I didn't realize it is so capable. When I return I'll have a look. As for the scope, I just don't know if I can manage something new in the budget. Even the 804 @ $439 is steep for my (initial) plans. And, it is out of stock, currently. When watching the Oscilloscope training vids I had myself convinced a used Tektronix would suffice. Is that not a good route to take? I'm a bit weary of buying used for such an important tool but I feel if I wait for the perfect tool at the perfect price I may never get started. Thoughts?* This advice is intended to save you time and money.Your consideration is much appreciated! Thank you.

author: donlisms
author_rank: Frequent Contributor
timestamp: April 15, 2024, 07:47:39 pm
content: There are many people who can't imagine relying on an analog Tektronix scope; it's not even digital! It does depend a lot on what you're doing, of course, and there are many people who *do* rely on them. I prefer my 485 as daily driver, unless or until there is some feature I need on the cheap digital scope.As to the fear of the unknown... you'd want to try and get as good a sense as possible of how well it's working before you buy, though there is always risk. I have a couple that were in great shape, and a couple that need work. The nice thing about it is the manuals are readily available and amazingly helpful. And while there may be obscure parts that fail, my guess is that you'd mostly need standard things like... capacitors. Plus there is a helpful community of experience out there. And videos. IOW, my view is once again "don't be scared." :-)I also very firmly believe that your projects in your bench will tell you when it's time to get more gear, as opposed to trying to predict the future and what you might need someday. This is not necessarily a popular view, and doesn't always line up well with the Joy of Acquisition of New Shiny Baubles!

author: wizard69
author_rank: Super Contributor
timestamp: April 16, 2024, 12:49:44 am
content: Quote from: MaxBishop on April 07, 2024, 08:59:10 amThat really isn't a lot of money to buy new. In fact I wouldn't bother with a lab supply.QuoteTimelines imply a project that is for money in most cases. As such it might make sense allocating more money for new hardware. On the flip side a project implies that you might know the exact voltages and currents required. If so fixed voltage industrial/commercial supplies are very cheap. You can literally find hundreds of such supplies from the regular distributors and they can be cheap.QuoteThere are numerous suppliers of lab type variable voltage supplies and they often come up for sale or auction. You can also go a bit upscale and get supplies used in test and measurement systems, often surprisingly cheap on auction or used. However the lack of information related to what makes this a pressing need really means we can't offer ideal advice.

author: Electro Fan
author_rank: Super Contributor
timestamp: April 16, 2024, 02:36:27 am
content: Quote from: MaxBishop on April 15, 2024, 05:12:31 pmStill not sure what your project and overall objectives are but I’d recommend making it fun and educational.One easy low cost way to do that if you are just getting started is to stick with DC circuits until you get comfortable with Ohm’s Law. For this you can postpone an oscilloscope.Just get the Korad and use your existing DMM(s). Get a couple breadboards, a package of LEDs, and an assortment of resistors, plus some 22 gauge solid wire, and a wire stripper - all easy to get on Amazon. Make simple circuits in various combinations until you can predict (calculate) what voltages and resistances will result in what current as shown on the Korad readouts and as confirmed on your DMM(s).Watch some youtubes and post your breadboard layouts and test results and questions here. Total investment less than $200 including the power supply. (Or to really save on the budget just use a 9V battery - but I think the flexibility and functionality of the power supply will speed up the learning process and make it more fun).When you get Ohm’s Law working as expected you can move on to capacitors or maybe transistors or other components, or maybe try an Arduino if you are interested in digital and software. Lots of cool and useful stuff can be learned and built without an oscilloscope. If you go this route and decide you need or want a scope you can revisit the used analog vs new digital vs bothdiscussion. Enjoy the journey.

author: MaxBishop
author_rank: Contributor
timestamp: April 19, 2024, 05:31:13 am
content: Quote from: wizard69 on April 16, 2024, 12:49:44 amThank you for the feedback, wizard69. My initial plan was to buy all used gear but it is looking like I may buy the KORAD for future testing but, for this project I'm using an Allen Bradley power supply.It isn’t something I’ll get paid for. Not the work I’ll put into it, anyway. It is something I want to use at work, though. Specifically, I want to prove there are other options than cost prohibitive industrial surveillance systems. I’ve considered using a PLC but I don’t know anything about the programming languages typically used.It’s only pressing because I’ve put a tentative completion date on it.

author: MaxBishop
author_rank: Contributor
timestamp: April 19, 2024, 05:39:52 am
content: Quote from: Electro Fan on April 16, 2024, 02:36:27 amThank you, Electro Fan. This sounds like a great plan for me. I'm going to utilize many of your suggestions. As far as my project, it's embarrassingly simple. I want to make a production machine surveillance system. The first step will be to count production pieces, input with one sensor and output with the other. Then, with some basic programming I can determine the % waste (raw material). If that all goes well, I’ll add another sensor at a different location in the process.

author: Electro Fan
author_rank: Super Contributor
timestamp: April 19, 2024, 12:24:53 pm
content: Maybe just learn/experiment/prototype with an “Arduino sensor kit” fromAmazon. An alternative to the oscilloscope would be a low cost (~$20) logic analyzer from Amazon or eBay plus free Pulseview software. The Arduino or Rasberry Pi are excellent platforms for learning the intersection of electronics hardware and software; Arduino is a notch easier if you haven’t done much/any coding. You can power the Arduino from a computer USB cable as you program it, so even the Korad could move to Phase II. If you get TEA syndrome you will probably recognize the symptoms.https://sigrok.org/wiki/PulseView