hybridfree/eevblog-posts huggingface dataset:
TEK 7a29 not showing trace or waveform - Page 1
Forum section: electronics / repair

author: Eth7an
author_rank: Contributor
timestamp: April 04, 2019, 02:15:35 pm
content: When I use my Tek 7104 scope which I just got with two 7a29 modules, only one of them works. Everything is good with the mainframe and I have tried swapping in and out different modules. The working 7a29 of course works on both left and right vertical channels of the mainframe, but so do some of my other vertical modules rated for 600mhz. When the broken 7a29 is in the mainframe and I select its channel and find beam, I can see it somewhere near the top of the crt. The position adjustment does nothing, unlike the working one which moves it even when find beam is enabled. It does sweep properly, so there is a trace, but with the working module in find beam mode, I can see the cal waveform, just a little blurry and small. The defective module shows nothing.If anybody has any idea on what could be wrong or what I could fix, that would be awesome!Thank you guys,Ethan
dell inspiron 1720 overheating - Page 1
Forum section: electronics / repair

author: quadzillatech
author_rank: Contributor
timestamp: April 04, 2019, 12:26:16 am
content: Hi all,im not sure if this is the corect section but here goes,ive the above laptop,it was a 1.73ghz proc,i swapped that for a 2.5ghz one along with 2x ssd drives,it is on win7 with 4gb ram,fitted the new proc and drives about 6 months ago and its been fine,now without warning it shuts down without warning,when i reeboot it says it shutdown due to it overheating,i stripped it down and cleaned the heatsink and replaced the compound,i actualy took the cover off of the fan to clean it,the spindle fell out with the impeller,i lubed it and refitted it,still no change,i got a new fan and heatsink today cleaned it all with acetone to remove the old thermal paste and put it back together,its still the same,it runs for about 2mins max before it dies,it doesent apear to get even warm tho and the fan runs at sort of medium speed,any ideas where to go next with it,its got me puzzled,i assume there must be a iffy temp sensor somewhere?,regards m3vuv.

author: quadzillatech
author_rank: Contributor
timestamp: April 04, 2019, 12:29:40 am
content: forgot to say it has all the latest drivers and bios update.
Help to identify the value of resistor - Page 1
Forum section: electronics / repair

author: Eldi4
author_rank: Contributor
timestamp: April 03, 2019, 04:48:44 am
content: Did anyone know what is the value of this resistor, the color coding does'nt make any sense for me, it was found on Delta Electronic DPS-220UB power supply, and the resistor is open-circuited.Red-Red-Gold-Gold-Black?, what?

author: Pete66
author_rank: Regular Contributor
timestamp: April 03, 2019, 05:11:16 am
content: I had a similar situation before after a week of trying to figure it out it turned out that the black band was only there to indicate the end of the resistor. So based on that I would guess its a 4 band resistor Red-Red-Gold-Gold and the last black band is only there to show where it ends. I could be wrong though

author: Eldi4
author_rank: Contributor
timestamp: April 03, 2019, 05:23:25 am
content: Well that is pretty reasonable, so it was 2.2 Ohm probably,what is your resistor looked like, where is it placed?

author: digsys
author_rank: Unknown
timestamp: April 03, 2019, 05:42:36 am
content: Not that it looks anything like the ones I've used, but 5 band values include tolerance (not black though), and 6 band ones include tempco - 250ppmBut that ones does not look like a precision one .. can you measure it?

author: Pete66
author_rank: Regular Contributor
timestamp: April 03, 2019, 05:46:10 am
content: I don't remember I think it may have been a CFL or LED circuit. I do remember spending a while trying to figure it out and it turned out that the fifth black band meant it was a non inductive resistor.So I treated it as a four band resistor and it worked out.You could try to find a forum where someone that has that same power supply and ask them to measure it for you.

author: Pete66
author_rank: Regular Contributor
timestamp: April 03, 2019, 05:50:42 am
content: I got bored and did a quick search on here and someone had the exact same question a couple of years ago.I think this will help you out.https://www.eevblog.com/forum/beginners/resistor-confusion/

author: Eldi4
author_rank: Contributor
timestamp: April 03, 2019, 05:56:12 am
content: Quote from: Pete66 on April 03, 2019, 05:50:42 amWell, i think it's clear, thank you very much

author: Gyro
author_rank: Super Contributor
timestamp: April 03, 2019, 09:09:54 am
content: Note the comments about it being fusible - any resistor that measures open circuit, with so little apparent damage, is almost certainly a fusible type. Replace with the same for continued safety.You also need to find out why it fused, otherwise the new one will almost certainly suffer the same fate.

author: David Hess
author_rank: Super Contributor
timestamp: April 03, 2019, 10:23:54 pm
content: Red, red, gold, and gold is 2.2 ohms and 5%. I assume the black band indicates a special feature like fusible or flame proof.
PACE ADS200 - Page 1
Forum section: electronics / repair

author: SMARTMULTI
author_rank: Newbie
timestamp: March 28, 2019, 10:09:35 am
content: Hello, accidentally smokes my new 110V PACE ADS200 with 230V acWith help from the forum have found a schematic for the unit to assist in the repair, however no mention of the secondary transformer voltage.Does anyone know what it should be?Thanks in advance.

author: Shock
author_rank: Super Contributor
timestamp: April 01, 2019, 03:39:39 am
content: Eventually got around to it.I measured 240V Primary 24V Secondary RMSNo significant drop between no load (PCB power cable disconnected) and idle (with no iron connected)Between 23-24V during a quick test of heating pulses (it bounces around).

author: SMARTMULTI
author_rank: Newbie
timestamp: April 03, 2019, 10:18:31 am
content: Thanks Shock, this one here seems to have taken a beating in that case, will have a 230/24 made up to replace the 110/24. Much appreciated.

author: SiliconWizard
author_rank: Super Contributor
timestamp: April 03, 2019, 02:51:02 pm
content: Does the unit have a primary fuse?

author: Shock
author_rank: Super Contributor
timestamp: April 03, 2019, 02:59:22 pm
content: Quote from: SiliconWizard on April 03, 2019, 02:51:02 pmIt does and they include a spare fuse if required.
SOLVED: Help identify SMPS controller ic - Page 1
Forum section: electronics / repair

author: montarbo
author_rank: Contributor
timestamp: April 02, 2019, 05:21:14 pm
content: Hello,Have at hands a Harman Kardon SMPS usb adapter with 3 usb output at 5V, 5A. Model number 5v-5c-5u.The power supply is totally dead. No blown fuse. Everything on as well secondary as primary sides seems fine, all caps checked with ESR spot on, every through hole (TH) component and SMD are good. Left to be checked is the controller ic which I can't find any info about.And no, no cold joint, went over every single weld with leaded solder just to be sure.The IC is a SOT23-6 package with two markings73E48a.762aAny ideas or info about the ic would be appreciated.BR

author: frozenfrogz
author_rank: Frequent Contributor
timestamp: April 02, 2019, 05:37:27 pm
content: These can be bought from China (look for 74E48 SOT23-6) - no idea about make and model or datasheet though.

author: montarbo
author_rank: Contributor
timestamp: April 02, 2019, 05:44:18 pm
content: Yeah I've seen those few sites and messaged one of the seller since yesterday if they supply datasheet with item. As a role its last resort to buy from china coz u never know what u get.

author: amyk
author_rank: Super Contributor
timestamp: April 03, 2019, 12:15:06 am
content: OB2273AMPConfirmation:https://www.aliexpress.com/item/10pcs-lot-OB2273AMP-OB2273A-SOT23-6-package-new-original-Immediate-delivery/32902341587.html

author: montarbo
author_rank: Contributor
timestamp: April 03, 2019, 02:45:56 pm
content: Quote from: amyk on April 03, 2019, 12:15:06 amThanks a ton.
Voltage standard range switch contact cleaning - Page 1
Forum section: electronics / repair

author: valley001
author_rank: Frequent Contributor
timestamp: April 02, 2019, 09:42:02 pm
content: Hi all,I am starting a separate thread on this topic since this is a (I think) mechanical issue.It seems the range selector switch on my Fluke 332D is unstable. If I switch between 10 and 100v ranges it will not settle back to the same reading with the readout at 0.000000, I see at least a 150uv deviation. If I apply counter clockwise pressure to the switch I can get it to bounce around fairly easily. I has been difficult to separate this issue from the electrical issues on my unit since some of the problems with settling 0 are/were due to bad caps.Attached is the type of switch. It has sealed contact wafers with access holes about the contact. I assume this is not the type of device to go spraying deoxit into..but I am wondering if I applied a little with a toothpick or something? I would hate to attempt to clean these contacts only to make the problem worse, advice/ideas are appreciated.

author: dacman
author_rank: Frequent Contributor
timestamp: April 02, 2019, 10:13:15 pm
content: The way I once fixed one of those gray boxes that had a non-repeating range switch was as follows:(I'm sure I tried to use some DeoxIT from a needle bottle, but that did not work.)1) I stood the unit on its handles and leaned it back some2) I took some LPS Contact Cleaner or IPA and saturated the switch (either will work as a contact cleaner, IPA will work in this instance)3) I exercised the switch several times (IPA or Contact Cleaner will cause the switch to start to bind)4) I took some LPS PreSolve and saturated the switch and exercised it several times5) I took some LPS-1 and saturated the switch and exercised it several times6) I repeated this for about 30 minutes or more (maybe an hour)7) This was done several years ago and the last I knew the unit was still working fineContact Cleaner or IPA can cause the destruction of the switch contacts so it will need to be lubricated.LPS-1 is classified as a dry lubricant, even though it is sprayed on.https://www.lpslabs.com/product-details/560

author: feedback.loop
author_rank: Frequent Contributor
timestamp: April 03, 2019, 12:05:15 am
content: I would suggest MG Chemicals contact cleaner with PPEhttps://www.mgchemicals.com/products/cleaning-products-for-electronics/cleaners/contact-cleaners/super-contact-cleaner-with-ppe-801b

author: valley001
author_rank: Frequent Contributor
timestamp: April 03, 2019, 02:20:13 am
content: Thanks all. Ill look into those products.
Weird posts under resistors??? - Page 1
Forum section: electronics / repair

author: anewmanx
author_rank: Contributor
timestamp: April 02, 2019, 08:56:22 pm
content: A few fusing resistors before a set of MOSFETS blew when a diode punched through on a HP 6034A power supply I'm working on. They are raised off the board with these weird posts. One set are just white insulators and it won't be a problem putting those on the replacement resistor. The ones that are weird are the metal ones from the picture.What do I do with those? Should I just solder to the old legs of the blown resistor and call it good? I've never seen anything like that.

author: tautech
author_rank: Super Contributor
timestamp: April 02, 2019, 09:20:22 pm
content: They're both just different types of stand offs that power resistors use to get them well away from the PCB to allow for better cooling.The metal ones should be flared (but not always) onto the tracks/pads on the bottom side of the PCB.Just use them again.

author: anewmanx
author_rank: Contributor
timestamp: April 02, 2019, 09:28:00 pm
content: Thank you so much for the quick reply. I didn't want to screw this thing up more than it already was.
Laptop LCD display brightness issue - Page 1
Forum section: electronics / repair

author: andyred
author_rank: Contributor
timestamp: April 02, 2019, 03:25:27 pm
content: Hello All,I encountered these days an issue which I've never seen before and I've repaired a couple of computers so far.The LCD display on a Asus N76VZ laptop is always on maximum brightness. Replaced the video cable with a new one, checked if this isn't an OS issue by reinstalling the same OS, another OS (Windows 10, Win 8, Win 7), in neither the brightness cannot be adjusted. Is like the OS is seeing the LCD doesn't have adjustable brightness. There is no OS setting either which is causing this.So it remains the hardware. I know when a display or inverter are going bad, display usually gets dim not stuck on maximum brightness.Perhaps some of you encountered this before and can provide some advice how to fix it.Thanks in advance
Systron Donner 7003 multimeter repair - Page 1
Forum section: electronics / repair

author: slotek
author_rank: Newbie
timestamp: April 02, 2019, 01:05:01 pm
content: Hi! I was given an old Systron Donner 7003 multimeter. I replaced old electrolythic capacitors, cleaned contacts and replaced a broken resistance selector switch.Now the multimeter measures resistace correctly, but fails to measure voltage and current. The display just flickers and shows incorect value.I was Googling for manual or schematic, but the search didn't return anything useful.Does anybodey have a schematic or manual for this instrument?
(Newbie alert!)  TPU for replacement rubber rollers in old audio equipment?? - Page 1
Forum section: electronics / repair

author: phuzzyday
author_rank: Newbie
timestamp: April 04, 2019, 11:22:07 pm
content: Hi everybody! Been watching and learning on EEVblog for ages, but just came into forum, so there is a risk of touching on something already discussed here... a quick search shows it may have been grazed before...I enjoy (trying) to repair old audio equipment, and of course there is a lack of supply of rubber parts, which have broken down into nothingness.I now have a 3D printer, and just ordered some TPU with the idea of making some rubber rollers! Has this been tried before? I have a .2 mm nozzle and a machine that can do .01mm layers.Thanks for any replies, and I look forward to joining into the conversations!!PD

author: DaJMasta
author_rank: Super Contributor
timestamp: April 08, 2019, 03:32:33 pm
content: I've made some parts from it to good effect, but it's going to depend a lot on your application. The TPU I used printed about the consistency of hard rubber (Sunlu brand), so while parts were pliable, they were fairly rigid even with lowish infill (20% or so). You can go lower or go to single layer walls to get more flexibility, but you probably want a softer material for good vibration damping or sealing applications (though, I wouldn't expect to get a real watertight or better seal out of a printed part). The problem is, of course, that softer materials are harder for your extruder to make work, so it becomes more important to slow down print speed and really make sure the filament path between the extruder gear and the nozzle is constrained.Regardless, with my cheap Sunlu TPU, a 0.4mm nozzle and 150um layer heights, I printed a bunch of feet and bumpers for a couple different kinds of equipment as well as some anti-vibration fan gaskets and things to pretty good effect. There's a thread in the Test Equipment section that has a bunch of 3D models that include those.

author: ebastler
author_rank: Super Contributor
timestamp: April 08, 2019, 05:55:57 pm
content: When you say "roller", do you refer to the drive mechanism in a tape drive or record player? (Pinch roller for the tape, or friction wheel to drive the turntable?) Those must be among the most critical parts to make, since the roundness directly impacts wow and flutter.Unless you have averyhigh resolution printer, you would need to put the parts on a lathe to finish the perimeter surface. I would probably avoid 3D printing at all, and rather try to make a mold from an original (but hardened) part, then cast replicas.
Two 68B09EP in a Sega pinball, Q and E are in paralel? - Page 1
Forum section: electronics / repair

author: powerchisper
author_rank: Contributor
timestamp: March 30, 2019, 03:55:22 pm
content: Hello friends.Still trying to fix the Independence Day Pinball.When I turn the machine on, all the lights in the playfield flash, on and off. Everyone in the internet says this is a communication problem with the ROM, RAM , etc.I did an experiment.The main board has two 68b09EP processors, one for the audio and the other one for the game code itself.If I swap them, there are not even blinking lighs, so I suspect that the audio's 68b09 is not working.My question is...is it possible that the sound cpu being bad can keep the machine from booting the game ?I saw the schematics and Q and E clock signals are in paralel to both processors, I don´t know if this is normal.Also noticed that AVMA signal is always high, don't know if this is good or bad.Got to this point thank to your help, I don´t have an oscilloscope, only a logic probe with 3 leds.Any hints on this ?Thank you in advance and, once again excuse me for my English I learnt from Beavis and Butthead.

author: james_s
author_rank: Super Contributor
timestamp: March 30, 2019, 04:34:35 pm
content: I don't think I've ever worked on a Sega pinball but in most machines the sound board is a completely separate subsystem and the game will boot and run without it connected at all. If the two CPUs are the same and swapping them changes the behavior then that's a pretty good indication that at least one of them is bad.

author: floobydust
author_rank: Super Contributor
timestamp: March 30, 2019, 04:59:20 pm
content: If swapping the CPU changes things, then you have a bad CPU or a socket/connection issue. Be careful of ESD, so you don't zap things handling the boards.The main CPU might hang waiting for a response from the Sound CPU, and that is what you are seeing.

author: stj
author_rank: Super Contributor
timestamp: March 31, 2019, 10:53:20 am
content: i dont know about whitestar or whatever you have,but on videogames it's common for the cpu's to come out of reset in sequence.so if the sub cpu does not start the main cpu will sit in reset waiting forever.

author: powerchisper
author_rank: Contributor
timestamp: March 31, 2019, 03:09:36 pm
content: Thank you all for your response.I already ordered a new cpu ( 68B09EP ) , it is not so easy to find.As you see I'm not an expert in this specific subject, but I have read everywhere that this system is sooo delicate !!!.It seems that it goes into perpetual reset even at the minimum trace resistance, bad sockets, etc.The reset is done by a DS1232, and it needs to be constantly fed with a bank select signal which depends on the adress bus.If this signal does not oscillate at a minimum speed, it will shut down the system.I will keep you informed, any other hints are welcome.
Fluke 15B+ cal eeprom dump - Page 1
Forum section: electronics / repair

author: modulate
author_rank: Newbie
timestamp: March 31, 2019, 09:36:20 pm
content: Hi. Does anyone have an eeprom dump of the cal data from U6? I am getting "Err" for a second on startup of the 15B+ meter so I'm assuming that I have messed up the eeprom somehow. Maybe overheated it doing a repair to a trace nearby. I know that the cal data won't be perfect for my unit, but maybe it's good enough and no more "Err". I can't find my eeprom programmer at the moment, so I can't check if I can read U6 manually. Could tthe "Err" message be related to something else?
Noise at the oscilloscope use voltage generator QW-MS3010D - Page 1
Forum section: electronics / repair

author: gtr
author_rank: Contributor
timestamp: March 27, 2019, 01:24:04 pm
content: Hello everyone,Lately I bought this voltage generatorhttps://www.amazon.com/QW-MS3010D-Adjustable-Stabilizer-Supply-Standard/dp/B07GCLK1R2thinking to use it to replace 1.5V and 9V batteries on fixtures .Unfortunately here is what gives to the oscilloscope with the generator on 9V in the first image and in the second with a 9V battery.Does anyone have the same problem with this QW-MS3010D?What can I do to remedy this noise?Thank you! :-)

author: jiarui
author_rank: Contributor
timestamp: March 27, 2019, 02:02:09 pm
content: I'm pretty sure it's a switching power supply. I have a similar unit. It's very cheap, but supplies 10A. It has pretty high ripple and switching noise. Use the scope to measure the power supply directly. You'll see the noise from the power supply. You should use a linear supply. Something like this one:https://www.amazon.com/Tekpower-TP3005P-Programmable-Variable-Regulated/dp/B06XCQN82X/ref=sr_1_4?crid=OKVALYGDUIMV&keywords=linear+power+supply&qid=1553695249&s=electronics&sprefix=linear+power%2Celectronics%2C130&sr=1-4

author: LateLesley
author_rank: Frequent Contributor
timestamp: March 27, 2019, 02:27:49 pm
content: do you have any inductors and capacitors laying around? You could construct a Pi filter on the powerline, and reduce the noise that way.https://electronics.stackexchange.com/questions/302052/best-way-to-filter-dc-dc-output-noisehttps://electronicscoach.com/pi-filter.html

author: gtr
author_rank: Contributor
timestamp: March 29, 2019, 01:27:58 pm
content: Hello,Thank you both for your response. The problem is only with the oscilloscope because the generator works well apart from that. If I connect my probe to another place in the mount, the signal to the oscilloscope is much better and virtually no noise.I'm going to do so for now while waiting to buy another linear voltage generator.Thank you! :-)
can you fix a very small pad on a pcb ?  - Page 1
Forum section: electronics / repair

author: vNawar
author_rank: Newbie
timestamp: March 28, 2019, 07:50:01 pm
content: there was a button like the other one in the picture but it broke off.is there any way to fix this?

author: helius
author_rank: Super Contributor
timestamp: March 28, 2019, 08:18:28 pm
content: It can be fixed with enough finesse and skill.The adhesion between the copper pads and the PCB substrate is broken, so adhesive needs to be used to reconnect pads to the board. A quick setting epoxy such as Araldite is frequently used for this. The new pads can be cut out of thin copper foils: pre-cut foils in several shapes are available from CircuitMedic and Pace Cir-Kit. Solder mask is scraped from the remaining traces and the foils are bonded to them using pressure and heat and solder.It is also possible to re-connect the traces by micro-soldering fine wires, or using silver conductive ink. The button needs to be supported by adhesive so it doesn't come off again.

author: DaJMasta
author_rank: Super Contributor
timestamp: March 28, 2019, 08:30:10 pm
content: Definitely possible, as said, but tricky because it's such small work. You need to get replacement pads (probably easier than removing and trying to reuse the ones on it) soldered to the existing traces - probably copper foil for the pad, then scraping away a bit of the solder mask and solder bridging them to the pads - then you need a reliable adhesive to attach the switch and hold it in place. Ideally, you want it to be stronger than it was before, since it already broke once, but you can't rely on the adhesion of the new pads to do as good a job as the factory ones, so some extra glue around it or in the board cutout would help to fix it.Again, though, it's probably going to take some time spent under a microscope/jeweler's loupe with a sharp knife and a bunch of patience. The hard part is actually doing it because of the size.

author: Wimberleytech
author_rank: Super Contributor
timestamp: March 28, 2019, 09:19:24 pm
content: I would solder 30 gauge wire to the switch contacts and then epoxy the switch in place. Then connect the other ends of the wires to the appropriate locations. Trying to rebuild the pads looks like a losing battle to me.

author: coppercone2
author_rank: Super Contributor
timestamp: March 28, 2019, 10:00:49 pm
content: you can dip the wire in tacky glue too. Wait for epoxy thats kinda starting to cure.

author: eKretz
author_rank: Frequent Contributor
timestamp: March 28, 2019, 10:22:03 pm
content: Yeah you should be able to get that fixed. I was thinking like super tiny smd cap pads from the thread title. That would be tough. This should be easy as long as you have the experience to do it, but still going to be time-consuming. It's fiddly work.
Searching for this flyback transformer Midcom 31592 - Page 1
Forum section: electronics / repair

author: Wimberleytech
author_rank: Super Contributor
timestamp: March 28, 2019, 08:00:26 pm
content: I need at least one, maybe a few of them. Trying to build a SMPS from an OLD datasheet calling for this transformer. Midcom is now owned by Wurth it appears. I have attached a datasheet, which itself was hard to find.This not really for repair, but I thought this was the best place to post
Fluke 87 Backlight issue... - Page 1
Forum section: electronics / repair

author: Pete66
author_rank: Regular Contributor
timestamp: March 28, 2019, 07:20:23 am
content: Hello,I've been lurking around this awesome place and finally decided to register.I have a small annoying issue maybe you guys can help me with. I recently purchased a broken Fluke 87 on ebay. I fixed it and calibrated it and it works great but there is still one annoying issue I cannot figure out. When I press the yellow button to turn on the LCD backlight it turns on no problem. However, when I press it again to turn it off it doesn't turn off. I have to turn off the meter to get the backlight to turn off. Pressing the yellow button again does not toggle the backlight off.According to the schematics Q5 and Q7 control the backlight. I tested them and they are both good. I'm not sure what the deal is. I'm beginning to think it is a firmware issue.Any ideas?Thanks,Pete

author: coromonadalix
author_rank: Super Contributor
timestamp: March 28, 2019, 11:22:08 am
content: may help ??http://mebert.org/entry/3

author: odessa
author_rank: Regular Contributor
timestamp: March 28, 2019, 12:22:33 pm
content: The older Fluke 87's work like that ( yellow button for backlight ) and it just stays on .The newer ones ( black button with illumination logo ) you can set to two brightness's then off again pressing the button.

author: mzacharias
author_rank: Frequent Contributor
timestamp: March 28, 2019, 12:23:54 pm
content: Normal operation for a series I. The backlight times out after about 52 seconds, if I recall.Or just turn the meter OFF and back ON again.

author: Pete66
author_rank: Regular Contributor
timestamp: March 28, 2019, 04:29:55 pm
content: I guess that's how it is supposed to work.ThanksPete
The Sh!# My Wife Brings Home - Fluke Multimeter Repair #2 - Page 1
Forum section: electronics / repair

author: retiredcaps
author_rank: Super Contributor
timestamp: March 27, 2019, 06:52:31 pm
content: At 5:25. "This fuse is gone and that's why its not reading the 12V".

author: ModemHead
author_rank: Frequent Contributor
timestamp: March 28, 2019, 12:54:28 pm
content: At least he did say start with the simple stuff first. That's good advice.As for the rest, well, subject matter experts are few and far between on Youtube. At least, as of this morning, I see we can use the date filters to find this crap once again.xkcd
ikea bekant electric table power supply repair - Page 1
Forum section: electronics / repair

author: RolandK
author_rank: Regular Contributor
timestamp: January 27, 2019, 09:36:20 pm
content: My ikea bekant electric table power supply had the folliwing error:It only moved 1 cm / a half inch, when pressing up or down.Reason: to move the table, the power supply changes the voltage from 24V to 35V.The used controller TEA1716 has a control loop supervision. While changing the Voltage the control loop supervision switches the power supply off.Adding a little Offset Current to the Opto Coupler helps. The blue Resistor is 47k || 330k. 47k alone or 33k work too.The control loop supervision is no more functional after the modification.As always: unplug the power cord when working at the supply. Only do this, when you are experienced with high voltage equipment and know, what you do. Electricity can cause injury or death.

author: RolandK
author_rank: Regular Contributor
timestamp: March 28, 2019, 07:56:31 am
content: As somebody asked:The added resistor makes a non-zero offset current in the optocoupler. Now the input voltage of the regulator ic stays within the limit of the open loop supervision.To get more load from the regulator, the current through the optocoupler is reduced. If the current is to small for a long time, the regulator ic asumes that the loop is broken and stops working to prevent an overvoltage situation and restarts after some time. The added offset current helps to stay on. But if the offset current is to big, you get not enought load.
Help finding a source for a miniature drive belt? - Page 1
Forum section: electronics / repair

author: cvanc
author_rank: Frequent Contributor
timestamp: March 27, 2019, 10:10:23 pm
content: Anyone here know a source for this small no-slip drive belt? My previous vendor (last used years ago) is out of business.I've got 2 compatible part numbers, one is F24CS-190 and the other is 24GCF-190-E Datasheets below.Thanks!https://www.pic-designcatalog.com/f24cs-190.htmlhttps://www.wmberg.com/products/belts-and-chains/row-l-er/1/24gcf-190-e?pcomSession=OKhttps://www.wmberg.com/berg/media/products/pdfs/B05A010.pdf

author: texaspyro
author_rank: Super Contributor
timestamp: March 28, 2019, 04:53:23 am
content: Try Stock Drive Products.
Looking for (service) manual of Ithaco 297eo lock-in amplifier - Page 1
Forum section: electronics / repair

author: NWerner
author_rank: Contributor
timestamp: March 27, 2019, 08:58:47 pm
content: I recently found some oldish lock-in amplifier. It seems to work ok. But I would liketo retrofit some options and capabilities not found in the original devicedoes anyone have a scanned copy of the service manual of the ithaco 297eo or similar?RegardsNorman
YAESU FT100 repair of Local-Unit board - Page 1
Forum section: electronics / repair

author: rjj100
author_rank: Newbie
timestamp: March 25, 2019, 02:33:59 am
content: I could use some help. The LO output on my FT100 is 94 mv p-p not 2.2v p-p into 50 ohm (11dbm) on 145 Mhz. The VCO is working, but I sometimes lose lock and the power output is about 1/2 w. on 2 m and 1-1/4 m.There are various filters and switching circuits but the schematic or manual does not identify which path is used on 2 m and 1-1/4 m. It would be helpful to know the rf voltmeter measurements on 2 and 1-1/4 m on this board. Can anyone help? NQ5P

author: rjj100
author_rank: Newbie
timestamp: March 27, 2019, 04:09:05 am
content: There is a lot of solder resin on this board, so I am going to clean it off best I can with denatured alchohol and then dry it well before preceding.I made a measurements after the first stage (Q2014 emitter), but it looks like there is no 9 volts powering the Q2031. Wondering if that is right on 146mhz on receive. It looks like any of the following signals could turn turn on the 9 volts .... BP, H1, H2, H3. What do these mean?If the 146 mhz signal doesnt go thru Q2031, then does it go thru d2054 and d2031?I really could use a good description of the functions and switching on this board.Aside, It is extremely difficult to read the board layout much less find the probe position on the board itself.
Help needed with Hanna Potentiometer PCB - Page 1
Forum section: electronics / repair

author: deandadnaed
author_rank: Contributor
timestamp: April 01, 2019, 06:13:19 am
content: Hi everyone!I’m a newbee here and I already got help and repaired my WR3M Weller Soldering Station.I’m on a new peoject. I’ve got a Hanna Potentiometer (aka pH meter) but despite of looking good, it has never worked, not even turned on.It runs in 12VDC. If i check the input, the Voltage does get to the PCB. The tesistance across the Fuse is <2Ohm.I’ve got no clue of where to start. Enviado desde mi iPhone utilizando Tapatalk
JBC handpiece - Page 1
Forum section: electronics / repair

author: xfs
author_rank: Newbie
timestamp: March 26, 2019, 10:02:31 pm
content: I have two broken 2245 JBC handpieces. One just stopped working a couple days ago. It used to get strangely warm at the point where the cable enters the plastic part. But it did that for years and worked fine until it just stopped. I've removed the rubber part protecting the cable trying to see if there was something suspicious where it always got hot, but it looks perfectly fine.The other one I bought used years ago, but I was never able to work with it. The cartridge won't go in all the way, 1-2cm missing. It seems like there is something stuck inside.What I wanted to ask is if anybody ever opened one of these up. The JBC support was no help unfortunately. I'm not sure it's actually possible without breaking it.

author: xfs
author_rank: Newbie
timestamp: March 27, 2019, 12:33:13 am
content: Eventually brute force and impatience took over, this is what it looks like:It came apart pretty clean. The two brass pieces hold the cartridge at the two plastic rings and make the contacts, the white part is a spacer between the two. The third wire is soldered to a cable that disappears inside the handle. Like I assumed the cable broke at the spot where it used to get warm, but it was a little more inside so I couldn't see it just by removing the rubber part. Cut the part of the wires off, soldered it back on, figured out how it goes together again, et voilà, working iron. Really didn't think it would be that easy.I opened up the other one with the blockage inside as well. It is constructed a bit differently, there are three metal pins that are fixed to a piece of plastic that makes up the whole diameter. They broke off clean from that surface, so fixing them will be tricky. Also I can't really get through from that side. I tried to push it out from the other side with a cartridge, but it didn't move. But now the cartridge sits as deep as it is supposed to... Will have to resolder the three pins and see if it makes proper contact or if something is still blocking inside.
TDS210 acrylic polarising film replacement - Page 1
Forum section: electronics / repair

author: gkmaia
author_rank: Frequent Contributor
timestamp: March 26, 2019, 09:26:46 pm
content: I had an issue with that thin film that covers both sides of the acrylic sheet that protects the LCD panel.I suspect that film is a polarising film. Can anyone confirm that and possibly give me some ideas on what to search for as a replacement?I've found some on AliExpress but not sure if they are that is the right one.https://www.aliexpress.com/item/Free-Shipping-2PCS-Lot-Original-10-4inch-135-degree-4-3-214MM-161MM-LCD-Monitor-Polarized/32961218196.html?spm=2114.search0104.3.22.4cb45ca2pPaTDw&ws_ab_test=searchweb0_0,searchweb201602_5_10065_10068_10547_319_10059_10884_317_10548_10887_10696_321_322_10084_453_10083_454_10103_10618_10307_537_536_10902,searchweb201603_58,ppcSwitch_0&algo_expid=82e67cc3-8066-4d6b-b0c7-0e89dd3dc1cb-3&algo_pvid=82e67cc3-8066-4d6b-b0c7-0e89dd3dc1cb

author: shakalnokturn
author_rank: Super Contributor
timestamp: March 26, 2019, 11:25:29 pm
content: I saw a TDS210 for sale for 80€ a few days ago with exactly those symptoms (huge blind spot in the middle of the screen), didn't bother with it as I had been through that once before.Yes the problem is the polariser peeling. The further problems are that it is stuck to the glass, meaning that it is hard to clean (I used White Spirit IIRC), and that when/if you find a replacement either it must be similarly stuck or spaced away from the glass to avoid "contact patches".I sourced some polarizer from a webstore some years back and was able to achieve a usable repair although nowhere near as good as the original for contrast and viewing angle.I think that the problem is the polarizers available are more specific to colour LCD's, possibly I only replaced the front polariser.

author: gkmaia
author_rank: Frequent Contributor
timestamp: March 26, 2019, 11:57:48 pm
content: Quote from: shakalnokturn on March 26, 2019, 11:25:29 pmSimilar issue. I managed to remove the polariser from both sides. If you look at the photo bellow the left one is the one without the film. It is less bright and only readable from an angle as you mentioned.Well, I just bought a 90degree one from Ali... lets see if that works.
Troubleshooting an HX711 IC in a digital scale - Page 1
Forum section: electronics / repair

author: Yamin
author_rank: Frequent Contributor
timestamp: March 26, 2019, 08:12:37 pm
content: Hi, I've got couple of Acaia digital scales used by baristas. The person who brought in the last one said that the measurements were off and I also noticed that the numbers were jumpy too. Anyway the manufacture states that its almost always the load cell which is effected. I tried swapping the controller board with another scale which had a good load cell. It didn't work probably the controller is calibrated in such a way that its supposed to be used with the load cell it came with.Anyway going to my question - I was wondering whether it was possible to troubleshoot an HX711 IC. I could get access to an oscilloscope in college. Maybe check the serial outputs?Thanks for the help
I need help hytera pd785g  - Page 1
Forum section: electronics / repair

author: elia
author_rank: Newbie
timestamp: March 26, 2019, 08:49:43 pm
content: Hello my beloved I am your brother from IraqThe device is operated when using the power supplyIt works properly but if we use the battery it works and then turns offWhat is the problem

author: shakalnokturn
author_rank: Super Contributor
timestamp: March 27, 2019, 12:54:02 am
content: Possibly the battery itself? Often Lithium polymer pouch batteries will bulge as a sign they are defective.With caution of short circuits, try running thin wires between the battery +/- terminals and transceiver, measure battery voltage while you operate the transceiver.
Xytronic 379 solder station - broken heater element - repair or replace? - Page 1
Forum section: electronics / repair

author: OccamsShaver
author_rank: Newbie
timestamp: March 30, 2019, 03:34:21 pm
content: Hello-Brand new to the forum. I have a Xytronic 379 soldering station that I've had for a number of years. It stopped working yesterday and I just found that the heater element is physically broken. Does it make sense for me to replace the element (it would cost me $25 shipped from the one vendor I found online) or just buy a new soldering station? One thing I've always disliked about the iron is that the plastic threaded cap comes loose if a little pressure is applied with the iron.I was just browsing Amazon for soldering stations. I was contemplating this Sealody SSA51.https://www.amazon.com/Digital-Soldering-Station-Aluminum-Cleaning/dp/B07MFPYSF6/ref=sr_1_6?keywords=soldering+station+digital&qid=1553959855&s=gateway&sr=8-6Any thoughts for this amateur? I typically use the iron to do occasional modifications and repairs to my guitars, amps, and various other small projects.Thanks,OS
Leader 3220 signal generator repair - Page 1
Forum section: electronics / repair

author: bob91343
author_rank: Super Contributor
timestamp: March 26, 2019, 02:05:17 am
content: This is such a nice generator when it works that I'd love to get it going again.It has lost phase lock it seems. The output started getting intermittent and it kept getting worse until it won't work properly no matter what. I get a lot of garbage in the output, although the attenuator still works.I have made an extender cable for the modules and even think I may have isolated the defective module, but I am stuck without more info.Has anyone worked on one of these, or even have a broken one with a good module I can buy?
ATX PSU repair - Page 1
Forum section: electronics / repair

author: Heyyy
author_rank: Newbie
timestamp: March 23, 2019, 05:25:20 pm
content: Hi,I have an ATX 450w psu that has bad caps(the bigg 200v ones that probably form the half bridge together with the chocke). I have some spares but they are half the nominal value of the original ones.I put them and the psu seems to work fine but the ripple levveles are high :200mv high and switching transients are way higher.I did the mesurements under slight load at bootup.Is this fix safe or i should relly struggle to find caps of the right value that fit? I don't think i'll push it beyond 200W.My other psu is a 500w model and uses 470u in series....what my new caps are.The old ones were a pair of 820u in series.Output voltages seem to be in speck or 10mV out.PS:The new caps are 200V each so the voltage rationg is ok.My concern is about the capacitance.

author: url
author_rank: Newbie
timestamp: March 23, 2019, 05:31:41 pm
content: HiI think you have answered your own question - the ripple levels are high.Plus - it should be repaired back to how it was designed... the correct caps must be around somewhere at the right price.David

author: Heyyy
author_rank: Newbie
timestamp: March 23, 2019, 05:39:30 pm
content: I have them.But they don't fit.The only form factor i found for their original value are short and too bulky.Does anyone know any tricks to make them fit?

author: coromonadalix
author_rank: Super Contributor
timestamp: March 23, 2019, 08:46:54 pm
content: I would not try to fit them if the size dont match .. my 2 centsadd longer leads to the caps ??

author: Heyyy
author_rank: Newbie
timestamp: March 23, 2019, 09:44:19 pm
content: I'll try the leads method and use longer leads ,but it's really cramped in there.Also ATX supplys what topology do they use?Since i saw 2 power switches and 2 caps + 1 chocke i belive it is a half bridge type?This way i'll know more about what cap value does to the output characteristics.

author: PKTKS
author_rank: Super Contributor
timestamp: March 25, 2019, 05:14:00 pm
content: Yes usually a half bridge but cheap models also use a switch110/220 which short cuts the virtual ground to the bridge rectifiermaking it considerable different from the usual half bridge split cap.If you are using 110 mode you have a different layout on the splitcap half bridge virtual ground.In other words the full bridge rectifier with split cap virtual groundis valid only on 220 inputs. On 110 a by pass switch cuts that.Not considering more expensive models w/ PFC supervisors....Paul
California instruments 1501IX-230 dip-switch settings - Page 1
Forum section: electronics / repair

author: Mr-Beamer
author_rank: Contributor
timestamp: March 22, 2019, 10:07:50 pm
content: Hey guys,I have tried to contact multiple Support Service Centres of California Instruments / Ametek that are listed on there website, but unfortunately none of them are responding on my question or the e-mail addresses are not correctSo I hope you can help me with a problem that I have with my 1501IX-230 AC and DC Power SourceThe right most Amplifier control board keeps blowing op its end-stage is randomly.My suspicion is that one of the Dip-switches is set wrong.And I cannot figure out the right settings from the user-manual.Model: 1501IX-230P/N: 1501IXB0D4X0000 Rev:AI use the unit standalone.The settings I have now are:Right (top) Amplifier control board:S1: ALL OFFS2: ALL OFFS3: 1 OFF MRR2 ON SLRLeft (bottom) Amplifier control board:S1: NR 1 is on the rest is OFFS2: ALL ONS3: 1 OFF MRR2 ON SLRUser manual:https://atecorp.com/atecorp/media/pdfs/data-sheets/california-instruments-751_1501_i-ix_compact_user_manual_6005-960_revl.pdfI think dip switch S1 is set wrong on the left amplifier (top one on the picture)(these are, as far as I know, 2 identical amplifiers in the master/slave mode)Page 107 :7.6.3.1 DIP SWITCH SETTINGSDIP switch S1 selects which oscillator phase will drive each half bridge.DIP SWITCH POSITION NAME FUNCTION1 LA ON for LEFT = Phase A (LB, LC must be OFF)2 RA ON for RIGHT = Phase A (RB, RC must be OFF)3 LB OFF) ON for LEFT = Phase B (LA, LC must be OFF)4 RB ON for RIGHT = Phase B (RA, RC must be OFF)5 LC ON for LEFT = Phase C (LA, LB must be OFF)6 RC ON for RIGHT = Phase C (RA, RB must be OFF)But this manual needs a manual to read it.So does anyone happen to know the settings or how I can get this info?Thanks in advance!

author: Mr-Beamer
author_rank: Contributor
timestamp: March 29, 2019, 10:55:35 am
content: I finally got a reaction back from the supplier:-----------------------------------------------------------------------------------------If you look at the unit from the front panel side.The master module is the one on the Right side.S1: 1 is ON the rest is OFFS2: ALL ONS3: 1 OFF , 2 ONThe secondary module is the one on the left side (I repeat if you look at it from the front panel side).S1: all OFFS2: all OFFS3: 1 OFF , 2 ON-------------------------------------------------------------------------------So my settings were good in themselves except that they were mirrored. (master-slave switched around)I don't think it matters much but I have now set it up in the "factory default" way.Hopefully he won't randomly blow his final stage out again.Don't want to place the IGBT's on the outside of this power supply for easy replacement
Bose AWRCC3 problem - Page 1
Forum section: electronics / repair

author: EMUD
author_rank: Regular Contributor
timestamp: March 14, 2019, 12:40:42 pm
content: Hi,I have a base AWRCC3 on my bench. When I turn it on it starts, shows "please wait" for some second and returns to standby.I have checked the well known problems (power supply electrolytics, dc switching transistors and pcb tracks), but there is no problem.The clock function is working, and the setup by remote control, too.I have checked the main pcb and the serial signals, the peripheral devices on this board (rds decoder, eeprom ppl control) were programmeddirectly after power on. I need a schematic diagram or service manual for this unit to look further. Please help !Thanks a lotEMUD

author: Waldi
author_rank: Newbie
timestamp: March 25, 2019, 02:03:21 pm
content: Hello, did you manage to solve? If so what was damaged? I have the same problem in the same device.
Tek 492p - Page 1
Forum section: electronics / repair

author: Deepak
author_rank: Regular Contributor
timestamp: March 22, 2019, 12:21:40 am
content: I picked up a Tek 492p that's about the same vintage as I am, and it seems to have some issues. I'm getting intermittent 'Error 60' messages, the trace seems to have a discontinuity it will either stop drawing halfway across the display (the peak/avg trace continues to make it) or there's a 2 or 3 division drop on the vertical scale depending on the setting I'm in.The physical display is nice, with a strong beam, and the overall fit & finish is quite good. Opt 1, 2, and 3 are loaded.I've pulled down the user manual as well as both service manuals and will be reading them tonight. The plan of attack is to pop the case this weekend, check the voltages, check all of the tantalum caps, then the rigid coax connections. 300 odd pages of replaceable parts sounds like fun.This is my first spectrum analyzer so I don't really have any idea what I'm doing. Any traps for young players I should watch out for?

author: 0culus
author_rank: Super Contributor
timestamp: March 22, 2019, 12:26:04 am
content: Not necessarily related to the repair, but since you say this is your first SA, be sure to pay attention to the input capabilities. Some SAs cannot tolerateanyDC level on the input. Others can tolerate some, just read the specs for yours. Inline DC blocks can help you out by ensuring AC coupling. If you're wanting to do something like look at your ham rig's key up characteristics,do nottransmit directly into your SA. Use a sampling tee and a dummy load.

author: Deepak
author_rank: Regular Contributor
timestamp: March 22, 2019, 12:51:05 am
content: Quote from: 0culus on March 22, 2019, 12:26:04 amUnderstood - there's a big red '0 V DC' marking right next to the input as well as a '+30 dBm max' warning that I'll try to be mindful of. I picked up a DC block which I plan to use until my beard is greyer and longer.

author: 0culus
author_rank: Super Contributor
timestamp: March 22, 2019, 01:02:50 am
content: Quote from: Deepak on March 22, 2019, 12:51:05 amThere you go...I believe in many cases (at least with the HP SAs I'm familiar with) it will take +/- 7 Vdc without damage (despite the 0 Vdc warning), but personally, I try not to play with fire.

author: 0culus
author_rank: Super Contributor
timestamp: March 24, 2019, 10:38:44 pm
content: Bumping this for the OP. Did you get a chance to pop it open yet?