hybridfree/eevblog-posts huggingface dataset:
TENMA 72-1095 Schematic or Knowledge Needed - Page 1
Forum section: electronics / repair

author: arattig
author_rank: Newbie
timestamp: April 07, 2022, 02:36:00 am
content: Does anyone have the Tenma 72-1095 schematic? Or URL to the file? Trying to troubleshoot this for far too long and out of ideas...Alternatively, if someone has had experience with the issue i'm seeing that would great to hear from you.Issue is when Line Voltage is selected, the output as measured on a multimeter, is adjustable by the variable transformer instead of directing 120VAC to the output. When Output Voltage or Output Current switches are selected, the output is as expected, adjustable by the variable transformer. My first suspect were the switches, these were removed disassembled and cleaned, although there was no indication of wear or tarnish. Their correct switching was also confirmed on a multimeter. All resistors are within tolerance, both diodes were replaced, both capacitors were replaced, no shorted windings on the primary nor variable transformers, op amp CA3140 was replaced....not many components here to be this stumped.Note, i was unable to positively ID one diode, it was glass, with the typical black band on the cathode, but absolutely no other markings under magnification. I replaced it with a 1N4148, which was physically smaller in size, so not convinced this was the correct diode, however i dont believe that if this diode failed it would cause my issue.Schematics, guidance, thoughts and general discussion welcome!!

author: arattig
author_rank: Newbie
timestamp: September 30, 2023, 08:47:52 pm
content: Uploading my Kicad schematic for future readers. My first attempt at Kicad, but should be very close to the actual design.

author: Smoky
author_rank: Frequent Contributor
timestamp: October 01, 2023, 09:17:55 pm
content: I also own a Tenma 72-1095 and I can't imagine pressing the "Line" button and expecting full mains voltage at the output.When I press the "Line" button I only expect to see the meter reflect the Line voltage to make sure that it's there and not sagging or misbehaving.Take a scenario that you're scrolling up the voltage on a project then you accidentally touch the "Line" button and it immediately delivers "magic smoke" style full mains voltage at breaker current to the output. There is no way Tenma would design a variac that way.Looking at the picture, every button in the circle relates only to the meter not to the output. I don't think there was anything wrong with your Variac.

author: arattig
author_rank: Newbie
timestamp: October 02, 2023, 01:46:40 am
content: Appreciate the response Smokey, and directions of use. I should of thought a bit more on the intent.Will consider this repair fixed....
Tenma 72-13210 (aka Korad KEL-103) DC load repair - Page 1
Forum section: electronics / repair

author: giosif
author_rank: Frequent Contributor
timestamp: March 25, 2025, 11:18:23 pm
content: Hi,I recently purchased a Tenma-branded DC load which is really a Korad KEL-103 and which is not working.After some quick testing, I am pretty sure the transformer is toast, but I am trying to confirm beyond any doubt.Q1: As such, could someone with either a Tenma or Korad DC load please measure the resistance of the two primary windings (out of circuit)?Mine measure 41.4 Ohm and 4.6 Ohm respectively.Also, the fact that there is no isolation between the two primary windings (again, out of circuit) makes me think something really bad must have happened.Q2: Any chance someone could measure the outputs on the secondaries of the transformer (out of circuit as well)?Q3: Any chance I can find a replacement transformer to purchase from Tenma or Korad?I've contacted Korad with this question (waiting for their response), but I could not find contact details for Tenma.Thanks!
Tenma 72-2690 Damaged After Connecting it to a Car - Page 1
Forum section: electronics / repair

author: aiq25
author_rank: Regular Contributor
timestamp: November 02, 2024, 07:20:10 pm
content: Hi. I accidentally damaged my Tenma 30V / 5A 72-2690 power supply. I did something stupid…I wanted to charge my car battery and hooked it up. While it was charging (after about 10 mins) the battery I tried to start the car. I knew I shouldn’t do that but thought the power supply would just go into current limit but it damaged the power supply.The CC light is on but no current output. The voltage is set to 13.8V but it doesn’t go up to that voltage. When I restart the supply, the voltage on the output slowly goes up to about 6V but collapses when there is any load.I plan to take it apart. Does anyone have any suggestions on where to look first?
Tenma 72-450 AC Millivolt Repair help? (GW Instek GVT-417B also?) - Page 1
Forum section: electronics / repair

author: Mixographer
author_rank: Newbie
timestamp: October 28, 2020, 06:12:22 pm
content: Hi All,I have a new to me Tenma 72-450 AC Millivoltmeter (same as, or similar to a GW Instek GVT-417B) that needs help. When I turn it on, the meter bounces to mid-level and back over about half a second, and then goes to full deflection. The range switch has no effect on this behavior. Leads connected or not, has no effect. Looking inside, everything looks good visually. It is really clean and all the caps look good, again visually. The relay works correctly as far as I can tell.Does anyone have a schematic or service manual for either these units. The manual list the only troubleshooting is to put in a new input fuse. There are many test-points on the board, but without a service manual, I don't know what I'm looking for. Has anyone seen a similar issue or repaired one of these?Thanks!Jimmy

author: Mixographer
author_rank: Newbie
timestamp: October 30, 2020, 07:12:59 pm
content: This may also be a copy of a Leader 181 AC Millivoltmeter.
Tenma 72-6905 (similar GW GPS-4303) Repair and schematic - Page 1
Forum section: electronics / repair

author: Irving
author_rank: Newbie
timestamp: November 28, 2020, 08:48:37 pm
content: My 2005 Tenma 72-6905 4-channel power supply bought for £75 on eBay a couple of years back finally threw enough faults to make me consider chucking it, but instead I decided to dismantle and troubleshoot it. I found the schematic for the Tek PS280/PS283 posted elsewhere but it soon became apparent this wasn't very representative though clearly they come from the same stable. Apart from the relay fault listed elsewhere (RL503 & 504 both OC coils - though given they are both low-power 2800ohm 24v relays running off a regulated 24v rail I find that hard to fathom), i had an o/c zener and a couple of electrolytics that were leaky, plus a few dry joints.Anyway, while I had it stripped down I drew up the schematic of each of the 3 pcbs in KiCAD, a PDF of which I attach here (mods: if it should go somewhere else feel free to move/copy it). It should be good for the GW-Instik GPS-4303, though the description of the serial/parallel options are slightly different to what actually appears to happen. Enjoy.

author: shakalnokturn
author_rank: Super Contributor
timestamp: November 28, 2020, 11:42:03 pm
content: Great work!I don't need it yet but thanks for sharing.

author: Irving
author_rank: Newbie
timestamp: November 29, 2020, 12:00:00 pm
content: You're welcome. Seems popular...

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: January 21, 2024, 09:06:38 pm
content: Must have been a huge amount of work- thanks so much. Don't know if I can fix my 4303, but will give it a shot.

author: duster
author_rank: Newbie
timestamp: June 19, 2025, 12:09:14 am
content: Thank you so much, it help me repair a GPS-4303C！

author: mrjoda
author_rank: Regular Contributor
timestamp: September 06, 2025, 06:08:22 pm
content: thank you ! I got broken GPS4303 and this will definetely help !
Tenma 72-8155 (UT 603) LCR meter - bin or repair? - Page 1
Forum section: electronics / repair

author: mianchen
author_rank: Regular Contributor
timestamp: November 24, 2013, 07:00:43 pm
content: Bought 2 x cheapo Tenma LCR meters off Toploser recently. One of them working the other does not measure L/C as described.These meters are exactly same as a UT603 shown inthis thread.After opened and poked around the faulty one, couldn't find anything obviously wrong with it. The only difference is that it draws 20+mA in L or C modes whereas the working one only takes <10mA. The 6V regulated rail reads 5.8V, 200mV lower than the 6.0V in the working one.I ended up wasting a lot of time measuring most of the components in circuit and compared that with the working unit - no difference. Swapping the 'daughter board' confirmed that the fault is on the 'motherboard'...Well it's still a good deal for 1 working unit. I don't want to waste more time on the faulty one and I'm gonna bin it (well maybe 'shelf' it and re-purpose it for something else). However before I do so, I'd like to ask here to see if anyone knows that this is a common fault and maybe an easy fix.(OT: If I want to buy an LCR meter I will definitely avoid these cheapo, doesn't do much, and give no confidence what-so-ever in the results you get from them. lowest range is 2mH, terrible for any uH inductor measurement.)Attached is a schematic I found on a Chinese forum. The L/C section of the UT603/Teman 72-8155 is identical to this. Almost all of the components and their values are identical. (sorry for the picture quality, couldn't find any better ones)

author: SeanB
author_rank: Super Contributor
timestamp: November 24, 2013, 07:25:11 pm
content: Have you checked the voltage rails. there is a -6V rail, and if it is missing you will have very unhappy chips and no working. Likely the 7660 is either not generating -6V or the TLO62 on the input side is fried. Otherwise check the oscillator is working on the 7106 and the 555 timer is oscillating at the right frequency.

author: PA0PBZ
author_rank: Super Contributor
timestamp: November 24, 2013, 07:25:21 pm
content: Since it doesn't do L or C, is the R measuring correct?If so maybe there's something wrong with the oscillator, did you measure/compare the output with a scope?It looks like the oscillator is theOP62TL062 somewhere in the middle of the diagram.

author: sombat3960
author_rank: Newbie
timestamp: September 30, 2024, 08:12:09 am
content: Hi,I know this topic very old but it will help if C/L not function.follow above previous advice to repair my ut603,the issue found is IC6(TL062C) under the LCD display in mother board is dead.replace it, then the reading value of measuring a known C value is correct.but the display shows with negative sign ( Don't know why).for the negative rail -6v,before replace about -2.xx to -3v.and after -5.69v.please advice to do next if there another issue.
Tenma 72-8340a calibration procedure?  <SOLVED> - Page 1
Forum section: electronics / repair

author: CaptKirk
author_rank: Newbie
timestamp: January 06, 2017, 03:13:52 am
content: I have a Tenma 72-8340a that is out of calibration. It outputs close to the voltage you set but displays the measured voltage wrong by around a volt or so at 12v. For example, you set the output to 12v, and it displays the output voltage as 11.3v but is actually outputting 11.7v (measured by a calibrated DVM).Looking around inside, I do not see any adjustment pots on the front panel or on the main board (that I noticed but I was concentrating on the front panel at the time).The current display is way off also, often just saying output is over 6 amps (the supply only does 1.6a).I've researched a ton on the web but I cant even find schematics or a calibration procedure online anywhere. Not even at Farnell.I think there are hidden options that the "manual" (more of a spec sheet than a proper manual) does not talk about. Powering up holding down the buttons get some interesting undocumented things on the display.It is a nice little bench supply and I would really like to get it working right myself. Anyone have any ideas?? I'd like to keep the LCD so a suggestion of putting a different display on it is not what I would like to do.Thanks.

author: CaptKirk
author_rank: Newbie
timestamp: April 26, 2017, 09:03:20 pm
content: Ok, I think I figured this out at least for voltage. You need a calibrated/accurate multimeter that you attach to the output. You then push and HOLD the voltage adjust button. The display eventually will show a value like "10". Turn on the output and see if the value shown on the screen is the voltage being output, if not, turn the knob and the voltage output will change (not the display on the supply) and just match the output to the value shown on the supply screen. Push the knob and it will the supply display will show a different value and just turn the knob until the multimeter agrees again. Continue. It goes through a few settings at different voltages near min and max. When you are done, the display set voltage you set will be VERY close to the actual voltage out for any setting. I have not yet figured out if there is a process for the current setting but I am thinking if the voltage is right, the current should be close also.

author: Tom Burton
author_rank: Newbie
timestamp: May 11, 2019, 03:33:53 pm
content: Thank you so much for this!Beentrying to find any information on this on the web. Will continue to play around and see what holding the current button does!

author: Macbeth
author_rank: Super Contributor
timestamp: May 11, 2019, 04:10:40 pm
content: Sorry I didn't find this earlier. Find the proper calibration procedure attached. These 20, 36, 60V Tenma supplies are also sold by Manson.
Terminal block screws - Page 1
Forum section: electronics / repair

author: gaminn
author_rank: Frequent Contributor
timestamp: June 12, 2024, 01:18:26 pm
content: Hi,any idea where to get screws like that? They come from this terminal blockhttps://www.phoenixcontact.com/en-pc/products/pcb-terminal-block-mkds-5-3-762-1704936. I have tens of these blocks on PCBs with screws damaged or missing. Desoldering the block from PCB and replacing it completely is one way to go but much more easier would be if just the screws are replaced. Do you think they can be bought somewhere (other than buying the whole terminal blocks and harvesting screws from them)?The screw is M3, total length 9 mm, the other side of the head (where it meets with the terminal block) is conical.Thanks

author: DTJ
author_rank: Super Contributor
timestamp: June 12, 2024, 01:39:03 pm
content: Similar to this?https://www.phoenixcontact.com/en-lt/products/screw-contact-screw-m3x7-h1l-1209788

author: gaminn
author_rank: Frequent Contributor
timestamp: June 12, 2024, 01:48:39 pm
content: Thanks. Maybe. It is not shown whether it has the conical part. The length of 7 mm should be OK if they measure it without the head. Unfortunately it seems the screw is hard to get.

author: 2N3055
author_rank: Super Contributor
timestamp: June 12, 2024, 02:14:29 pm
content: Replace terminals.Damaged screws mean abuse of the block. You cannot easily tell in what shape inside is.

author: gaminn
author_rank: Frequent Contributor
timestamp: June 12, 2024, 02:22:05 pm
content: Yes, if the screw are impossible to buy, I will replace the whole terminals. But to be honest, the terminals are OK, only the screws are missing or damaged because someone can't use the right screwdriver....
Tes 6220 60v/3A power supply - Page 1
Forum section: electronics / repair

author: diag7919
author_rank: Contributor
timestamp: May 29, 2020, 02:05:44 pm
content: Hi, anyone got a circuit for this ps, it's failed and there's plenty of modern components that I feel don't belong in there, the 3 series elements are BU208A, the driver transistor, which is short a TIP41C, R23 is several power resistors in parallel, think that's all I've found.. It worked for a short time until I asked for a bit more power, that's when it decided to give me 70v++. Any help identifying these parts or better still a circuit... Oh. That would be great.Cheers...

author: coromonadalix
author_rank: Super Contributor
timestamp: May 30, 2020, 02:45:13 pm
content: Internals Photos ??Maybe it could have some ressemblance to other brands ?I had Topward in mind

author: diag7919
author_rank: Contributor
timestamp: May 30, 2020, 03:28:00 pm
content: I have removed series transistor / heatsink assembly.. All I can find on this is from...http://www.twtes.com.cn/en/product/pro72.html
Test equipment for servo motor - Page 1
Forum section: electronics / repair

author: marc.hickling
author_rank: Contributor
timestamp: April 11, 2021, 11:35:56 pm
content: Hey all. I work at a repair company and we repair servo motors we currently use a mitchell electronics test system to align and test feedback on the servo motor (encoder, resolver etc). Does anyone know of any other test systems out there? I cant believe they are the only one but they are the only one I can find. Ie how are servo motors repaired and tested in Asia?
test gear  display help - Page 1
Forum section: electronics / repair

author: m3vuv
author_rank: Super Contributor
timestamp: January 19, 2021, 09:41:13 pm
content: just came across this on one of the forums i visit,i thought it may be of use to folks here?:https://tabajara-labs.blogspot.com/2021/01/como-ligar-um-monitor-vga-no-hp-e8285a.html its in english if you scroll to the bottom.
Test individual GPU phases ? - Page 1
Forum section: electronics / repair

author: didi79
author_rank: Contributor
timestamp: May 29, 2021, 09:44:17 am
content: I'm rebuilding the GPU VRM on a GTX 970. It has 6 phases.All phases are grouped on the output (usually at the inductor end facing the GPU). How do I know that each individual phase works ? Is removing the inductors (in fact isolating each phase from the group) the only way ?Good diagram from the datasheet of the multi phase buck controller:

author: TheMG
author_rank: Frequent Contributor
timestamp: May 29, 2021, 03:54:59 pm
content: Scope the input (switched) side of the inductors.

author: didi79
author_rank: Contributor
timestamp: May 30, 2021, 07:58:59 am
content: I hadn't thought of that. Thank you.I really need an oscillocope !!
Test instruments/ Fluke 199 failure to display the signal in the CH2 - Page 1
Forum section: electronics / repair

author: azemati
author_rank: Contributor
timestamp: February 17, 2020, 11:51:33 am
content: GreetingsI have an oscilloscope (Fluke 199) that unfortunately has a second channel that is out of order and does not display any waveform.I checked and found that IC OQ0260HL from Philips was not working at the entrance to this channel,Please guide me to:Is there a replacement part for this IC?Do you know any supplier for it?Does anyone have the experience of repairing this model?please advice me

author: michal82
author_rank: Contributor
timestamp: April 05, 2020, 12:19:26 pm
content: HelloI have 196 with two damaged channels.I would like to replace the OQ0260HL integrated circuits but I don't know where to buy it.Did you buy somewhere?

author: azemati
author_rank: Contributor
timestamp: April 05, 2020, 01:02:55 pm
content: I’m looking for the integrated circuit too, but I couldn’t find it yet (OQ0260HL)
Test PROM for Philips PM5390S - Page 1
Forum section: electronics / repair

author: giosif
author_rank: Frequent Contributor
timestamp: October 08, 2020, 06:04:59 pm
content: Hi,I am trying to repair a PM5390S RF synthesizer and the manual mentions a test PROM which allows one to do several checks.Does anyone here happen to have this PROM available and willing to share, please?A Google search didn't reveal anything useful.Thanks!

author: Emo
author_rank: Regular Contributor
timestamp: October 08, 2020, 06:27:02 pm
content: Hi Giosif,I did a repair and upgrade on this synthesizer some years ago. Unless the processor or keyboard is at fault I don't think you will need the prom. In chapter 7 of the service manual a detailed checklist will bring you a proper working instrument.In my unit a lot of electrolytics inside the closed synthesizer unit were bad.Originally my unit was a regular one and using the included print layout in the service manual I build the power amplifier myself, power supply already being prepared for that, so now i have the -S version. The altered software can be switched by jumper.Eric

author: giosif
author_rank: Frequent Contributor
timestamp: October 08, 2020, 08:13:34 pm
content: Hi Eric,Fair enough.Two other questions, if I may:1. Do you know how to remove the plastic cover of the power button?Step 2 in section 4.6 of the service manual says to do that in order to get the keyboard/display unit out, but I'm not sure how and I would like to avoid breaking any plastics.2. What did you replace the SRAM battery with?Thanks!

author: Emo
author_rank: Regular Contributor
timestamp: October 09, 2020, 12:18:54 pm
content: Hi Giosif,The chrome plated outer ring on the power supply switch is actually a nut in disguise. So carefully gripping it with pliers and some protective material in between you can screw it of.The SRAM battery can be switched on and off by the jumpers on the back. It contains three NiCad cells that will be charged during use. Any 3,6 V model will work. In my case some life was left in them so I was lucky. Working without is no issue as it only stores the presets.And this is where the magic happens inside the closed box

author: giosif
author_rank: Frequent Contributor
timestamp: October 11, 2020, 09:52:52 pm
content: Thank you, Eric!I eventually unscrewed that ring, although it wasn't as simple as gripping it and turning it counterclockwise.With regards to the battery, I am evaluating the options, as I am reluctant to install any NiCd / NiMH batteries which might leak at some point.I eventually mustered the courage and opened the big & heavy box and, funnily enough, checking the electrolytic caps in there, almost all of them had less than half their rated capacity, although their ESR was ok.I replaced the caps and re-assembled the box.On to the display unit now...
Testing components on a motherboard rigol. - Page 1
Forum section: electronics / repair

author: GGMM
author_rank: Frequent Contributor
timestamp: October 04, 2023, 01:42:29 pm
content: hello,Is it possible to test components on a Rigol 1052E motherboard ( and probably others) with JTAG?For example, can we test the H57V1262GTR-75C HYNIX ram?and how to do?EX an article:https://www.xjtag.com/wp-content/uploads/xjtag-ppt_memory-testing-programming-en.pdfcdt
Testing CRT from scope ? - Page 1
Forum section: electronics / repair

author: lordvader88
author_rank: Frequent Contributor
timestamp: July 09, 2019, 01:44:24 am
content: I bought a broken vacuum tube oscilloscope scope that was dropped, (turns out the transformer is burnt out too). The CRT was knocked when it dropped, and there's even a little bit of debris of something loose inside.Actually the whole PCB cracked in have and 2-3 resistors. I fixed all that, then discovered the trans was shorting.I have DMM, LCR/ESR meter, scopes. Is there any low voltage tests I can try to determine the state of it ? I have various HV sources, but I'm not messing with any of that yet

author: Ian.M
author_rank: Super Contributor
timestamp: July 09, 2019, 02:25:42 am
content: Not really. The only things you can check for with low voltage testing is if the filament is intact or if there are any obvious inter-electrode shorts. It wont pick up if the electron gun has been knocked out of alignment, or damage or distortion affecting to the deflection plates or to the acceleration gauze if the tube is a high sensitivity deflection one. Even if you were prepared to apply the correct voltages to the gun and final anode, to check it produces a focusable beam, unless you have a full deflection system + something to drive it to produce a grid pattern, you wouldn't be able to test for geometry errors.
Testing DVI after surge  - Page 1
Forum section: electronics / repair

author: Chris2019
author_rank: Newbie
timestamp: September 10, 2019, 02:10:00 pm
content: There was some sort of transient electrical issues which appears to have damaged an LCD monitor and attached Fujitsu mini PC. DVI is dead on both, but the PC works fine otherwise (can login via remote desktop). I've ordered spare power and video boards for the Lenovo LCD and will change both to be safe.The question is, how can I test the DVI port on the PC (to determine if it is really dead or just the screen) without possibly destroying the new monitor parts? Is there a way or is there even much risk in just plugging it in seeing what happens?Thanks!

author: SilverSolder
author_rank: Super Contributor
timestamp: September 11, 2019, 12:19:55 pm
content: 1) Hook the monitor up to a known working PC to see if the monitor still works,2) Hook a known good monitor up to the PC to see if the PC still works?
Testing mosfets in an Hifi Amplifier - Page 1
Forum section: electronics / repair

author: drewt86
author_rank: Newbie
timestamp: May 15, 2019, 01:02:23 am
content: I spent the better part of a day tracking down issues in a Hafler 9505 that came in over the weekend. Most of the problems were pretty easy to spot. Burned up bias resistor on the output mosfets and a shorted driver transistor. The driver section of the board suffered from some pretty bad burn on the board so I decided to bring the bias down from 400ma to 300ma. I also whacked some TO92 package heatsinks on to the them to give the board a break from sinking all the heat. Today when I turned it on to test it out, my fuses went in the output stage. I'm starting to suspect I have a shorted output mosfet in the array. These things are hard as hell to find so I hope they're not fried.What are some techniques used to test mosfets? Is it possible to test these in circuit? Do they normal fail short or open?Thanks in advance.I've attached the schems for the 9500 as well since it's identical from the driver section on to the 9505 and the schems provided on Hafler's site are practically illegible.

author: coromonadalix
author_rank: Super Contributor
timestamp: May 15, 2019, 01:23:14 am
content: https://www.utm.edu/staff/leeb/mostest.htmhttps://www.diyaudio.com/forums/solid-state/96744-test-mosfet.htmlhope it help

author: drewt86
author_rank: Newbie
timestamp: May 15, 2019, 01:27:22 am
content: thanks for the reply. I love Allan's youtube channel. I actually came across this video. For whatever reason, I'm not getting the same results he's able to get in the video on any of these mosfets. I assumed they're something different about what they've used in this board.
Testing repaired PCB tracks for current carrying capacity - Page 1
Forum section: electronics / repair

author: ThermallyFrigid
author_rank: Frequent Contributor
timestamp: September 04, 2022, 03:54:51 pm
content: Hello,I do a fair amount of PCB repair and while most of the time the repairs are successful, I never have tested the tracks or vias I've repair for their actual current handling characteristics.I'm wondering if I should and if so, how you do this for individual vias and repaired tracks.Thanks

author: m k
author_rank: Super Contributor
timestamp: September 10, 2022, 03:35:00 pm
content: I've also done some.You should do the repair so that there are no doubts.We used flatted wires that were equally wide.Then thickness of the repair is always more than original.Flattening is obviously possible only up to a certain width.After that wires were left round, same when flattening was not suitable.But since that was pro stuff very wide situations didn't happen very often.Those were usually doomed and scrapped.High frequency is another thing.There you must start thinking how the correction affects the signal path.General rule was to follow original route.
Testo 560-1 pressure sensor  - Page 1
Forum section: electronics / repair

author: DarkZero
author_rank: Regular Contributor
timestamp: September 06, 2020, 12:14:19 pm
content: "Blue" side sensor shows wrong pressure value and when i zero the pressure values it does nothing when i switch the sensor places now the "Red" side reads wrong values (see attached pic's) so that tells me something went wrong with sensor not the main electronics.error is not linear meaning if working one reads 1 bar the other one doesn't read 1-0.4bar and error seems to change over time.anyone heaving experience how to approach fixing this? clear coating on sensor can be removed easily since its some very soft silicone or something

author: TheMG
author_rank: Frequent Contributor
timestamp: September 06, 2020, 02:27:42 pm
content: Chances are it's probably going to be the pressure sensor element itself that is defective. I'm assuming it's on the other side of the board as all I see in the picture is an instrumentation op-amp and some passives.

author: DarkZero
author_rank: Regular Contributor
timestamp: September 08, 2020, 01:08:59 pm
content: yes i was going to give up and started searching on internet for replacement sensor, but then i removed coating and measured one of the capacitors as short i checked on the other there wasnt short. it was a 10nf one which i replaced i didn't think it will work but i assembled it and tried to zero it and to my surprise it worked ....i made vacuum to check accuracy and it was working ok i don't know what to think of this repair, extreme luck.
Teufel IP 42 RC audio receiver with DC on its outputs (TDA7265) - Page 1
Forum section: electronics / repair

author: Kirkhaan
author_rank: Frequent Contributor
timestamp: August 19, 2024, 11:01:13 am
content: I have here a Teufel IP 42 RC receiver that has about 150mV DC on the loudspeaker outputs.The DC level is constant and does not change with volume settings and it is causing an irritant plopping sound when changing input source or when switching on/off.It has the TDA7265 amplifier IC embedded and I am considering replacing it, since it must come from this end-stage IC I assume.https://www.st.com/resource/en/datasheet/tda7265.pdfAnyone experience with DC offset and TDA7265 amplifier IC's?Thanks!

author: Kirkhaan
author_rank: Frequent Contributor
timestamp: August 22, 2024, 06:42:13 pm
content: Well, I have replaced the TDA7265 by a brand new one (~€4), but the DC offset of approx. 150mV is still there...Now I am a bit puzzled, because its inputs are AC coupled and there is no means (as far as I understand) to tune the power stage bias, see below application circuit, which is almost 1:1 implemented in the Teufel amplifier.Anyone advice or suggestions? Thanks!

author: DaJMasta
author_rank: Super Contributor
timestamp: August 22, 2024, 07:50:15 pm
content: You could just AC couple the output too, but isn't the popping usually due to zero crossings/spikes on the input? Maybe you can add a few ms of delay before unmuting after initialization and switching? Is the ground on pin 9 a good analog ground with your input source?

author: Kirkhaan
author_rank: Frequent Contributor
timestamp: August 27, 2024, 07:44:32 am
content: Thanks for your suggestions. They didn't make any difference unfortunately.Its even there when the inputs are shorted to ground (and I've confirmed a solid analog ground).The supply rail is perfectly symmetrical (+23.45 and - 23.44V).It seems this 150~200mV DC on the output is the best this TDA7265 can do.Quote from: DaJMasta on August 22, 2024, 07:50:15 pm

author: Xena E
author_rank: Frequent Contributor
timestamp: August 27, 2024, 08:01:59 am
content: It may* be possible to trim the output by applying a small DC offset directly to the input pins.*Never tried it, just a thought.
Teufel makes a fully repairable portable speaker - Open Source - Page 1
Forum section: electronics / repair

author: Haenk
author_rank: Super Contributor
timestamp: July 18, 2025, 09:38:25 am
content: Geman manufacturer "Teufel" decided on creating an Open Source portable speaker, with schematics and repairablity in mind:In German (use the translator of your choice):https://www.heise.de/hintergrund/Die-Entwickler-des-Open-Source-Lautsprechers-Teufel-Mynd-im-Interview-10490607.htmlSupport page:https://teufel.de/mynd-107002004#pdp-supportThey even offer the firmware as source, CAD files, PCB files etc.What a great idea, IMHO.
Texas Instrument mid-1960's germanium pnp TO5 data lookup from TI part # - Page 1
Forum section: electronics / repair

author: trobbins
author_rank: Frequent Contributor
timestamp: October 21, 2021, 03:39:09 am
content: Would anyone have either vintage TI semiconductor data from the mid-1960's, or a cross-reference handbook, that identifies two pnp germanium TO5 metal can bjt's with TI part # 650859-3 and 651236 ?Those bjt's are in a Wurlitzer organ reverb module from circa 1965. All the transistors are fine - I am just trying to locate data for them, as they don't have a Jedec part id. The NTE cross-reference app only associates both those transistors with their NTE-102 part. No googling so far has shown up any relevant reference to those part #s used in other equipment, or in cross-references, and I don't have hardcopies any more of the semiconductor reference lookups.Ciao, Tim

author: fzabkar
author_rank: Super Contributor
timestamp: October 21, 2021, 04:19:39 am
content: FWIW, this databook is from 1972:http://www.bitsavers.org/components/ti/_dataBooks/1972_TI_Power_Semiconductor_Data_Book_First_Edition.pdfI suspect that your parts are custom orders.

author: trobbins
author_rank: Frequent Contributor
timestamp: October 21, 2021, 04:38:31 am
content: Thanx - yeh I just deciphered a fuzzy part of a Wurlitzer schematic that indicates they were Wurlitzer part numbers - so that covers my request.
T/H BLE receiver - Blowed up good...Blowed up real good! - Page 1
Forum section: electronics / repair

author: DrG
author_rank: Super Contributor
timestamp: February 04, 2021, 04:36:51 pm
content: Going on ~two years ago, I built a little four channel, BLE receiver for remote humidity and temperature monitoring. The receiver is an ESP32 with a generic 4X20 LCD. It has been working like a charm and I am real happy with the project. Yesterday, however, I walked across the carpet, grabbed the unit, touching one of the four mounting screws that connects the LCD to the case and...bzzzzt...static electric shock and instantly the screen went to those tell-tale squares where other characters should be. Resetting power produced no change.After disassembly and further investigation, I determined that the 4X20 was fried and the ESP32 was fine. I happened to have another LCD and replaced the bad one and all is well.Looking at the back of the LCD board, notice J1 and J2 solder bridge jumpers (they are not bridged). Also, each of the four mounting holes are connected (obverse side of the board and not shown). Thus if I connect J2, I would connect all four mounting screws to the ground plane.Would that have make a difference? In general, is it a good idea to do so in a project with mounting to a case like this?PS: I realize that the LCD screen may still be intact and something on the I2C board may have blown. I will investigate that possibility at some time in the future.PPS: With regard tohttps://www.eevblog.com/forum/chat/i-constantly-getting-shocks-from-electrostatic-charge-what-can-i-do/I favor misting diluted liquid fabric softener and regret not having done so.

author: TheMG
author_rank: Frequent Contributor
timestamp: February 04, 2021, 04:58:39 pm
content: You also need to have a good low impedance path between the ground plane of the LCD module and the common/ground of the rest of your circuitry, and ultimately all the way to the ground/common of the power supply.ESD discharges have a very fast rise time and wires will behave as inductors, allowing potentially damaging voltage differences to occur during ESD events. So keep impedance (inductance) to a minimum. In a metal enclosure this is not a problem as the enclosure provides a nice low impedance path, but in plastic you need to bond different boards/modules with larger gauge wire or even copper braid or copper tape.

author: DrG
author_rank: Super Contributor
timestamp: February 04, 2021, 05:04:29 pm
content: Quote from: TheMG on February 04, 2021, 04:58:39 pmWould connecting GND to a large (say a five or six hole width) piece of copper tape on the circuit board help?
Thandar TG2001 Function Generator Repairs - Page 1
Forum section: electronics / repair

author: Orion63
author_rank: Contributor
timestamp: February 07, 2022, 02:37:33 am
content: Hi, I bought this Thandar TG 2001 function generator from a local garage sale. However, when plugged it up, I could see the display responding well for the changes in the Frequency, Amplitude and the Offset knobs. But I do not get an output from the Main Output BNC or the TTL BNC. I have checked the DC voltages +21V, -21V, +16V, -16V, +12V, -12V,+5.2V and the -5.2V on the board, and they are spot-on correct. I don't see any visual damage, like burnt resistors or transistors on the PCB.Any suggestions on what to look for ? Can anyone share a schematic/service manual if possible ? Regards

author: 45Overload
author_rank: Contributor
timestamp: February 09, 2022, 03:56:36 am
content: Orion,Function Generators often have d.c. coupled output stages which will blow up if the test leads are accidentally shorted or if they are accidentally connected to a voltage source. I would check the output stage parts with the schematic that I know you have!-45O
Thandar TM351 - First repair - Page 1
Forum section: electronics / repair

author: Hammie217
author_rank: Newbie
timestamp: February 26, 2020, 04:14:42 pm
content: Hi all,This is my first repair attempt, I picked up a thandar TM351 and TM355 and some Fluke multimeter for £30 for an attempt at repairs.The TM351 is in fairly good nick except for a small battery leak that seems to have damaged the screws more than anything else. The meter seems to work well on some modes but others not so much (Table of buggery below (X shows not correct)). Some of the higher ranges are taking a while to settle but I'm assuming that's normal.DC:0.2220200200020000OhmsAmpsVoltsxxxxAC:0.2220200200020000OhmsAmps(all reading the same)xxxxxxVolts(all reading the same)xxxxxxThere are datasheets online here:(https://www.kevinchant.com/uploads/7/1/0/8/7108231/thandar_tm351-workshop-manual.pdf) but any help as to what to look for would be greatly appreciatedThanks,Hamish

author: tekguy
author_rank: Contributor
timestamp: September 25, 2022, 10:53:13 pm
content: i have the same issue,no answers?.
The lights on the Xbox 360 controller are flashing, I press the sync button and  - Page 1
Forum section: electronics / repair

author: david smth
author_rank: Contributor
timestamp: March 02, 2025, 11:33:00 am
content: The lights on the Xbox 360 controller are flashing, I press the sync button and it spins but the Xbox 360 controller does not connect to the machine, the controller works, where is the problem? Is the oscillator faulty or the Eeoprem chip?

author: david smth
author_rank: Contributor
timestamp: March 02, 2025, 11:37:11 am
content: The lights of the Xbox 360 controller are flashing but it is not connecting. The lights are constantly turning and it is not connecting.
The memory holder is broken - Page 1
Forum section: electronics / repair

author: Hextejas
author_rank: Frequent Contributor
timestamp: April 28, 2020, 03:02:51 pm
content: Its a dell D510 that I am trying to repair. It was working ok with 2x512 ram chips. I bought 2 expansion chips, 2x1024 and when taking out the old chips something happened to one of the tiny connectors in the memory holder. I am not sure if you can see it from these photos cause its tiny and my cell phone camera had a hard time focusing.Anyway here it is and I was wondering if I could replace the memory holder (I am not sure what to call it and I cant see how I would remove it), or should I try and solder the broken connector back in. The soldering job scares me.

author: dicky96
author_rank: Regular Contributor
timestamp: April 30, 2020, 12:15:41 pm
content: Hard to say from those pics but it looks like you may be able to push the pin back into the RAM socket, resolder it and secure it with a bit of hot snot glue or resin.If not you can buy DDR2 SO-DIMM sockets easily and cheaply, just google for that. I htink form your pics that is what the socket is. Then it would depend on your soldering skills and equipment. If soldering 'scares' you then probably you should not be fixing laptops...
The model of NF1A PNP transistor - Page 1
Forum section: electronics / repair

author: teatime
author_rank: Contributor
timestamp: July 09, 2025, 08:33:26 am
content: This is a PNP transistor, marked"NF1A"the NPN transistor, marked"NF1C"But I can't find the real model of NF1A .This is a product made in JAPAN.I wish some one can tell me the result.Thanks
the next generation of thermal camera - Page 1
Forum section: electronics / repair

author: coppercone2
author_rank: Super Contributor
timestamp: November 26, 2023, 10:34:25 pm
content: So a while back I found a video of a pen that puts flux fumes on your PCB, so you can see hot spots.however this technology was too bloated and costly, so it looks like this new version was developed, and you can even use kief if you are in the correct area where its cheaper then flux.So they just powder flux really good and dust a PCB with it. It does have the advantage over thermal where the heat signature persists for a infinite amount of time, meaning you don't have to deal with photographs anymore.https://youtube.com/shorts/2LUEMUPlAdc?si=pz5dnMHbNtSTQLfP
the piece in the picture - Page 1
Forum section: electronics / repair

author: brkklcl
author_rank: Newbie
timestamp: December 16, 2024, 08:02:53 am
content: Hello, does anyone know what the part in the picture is? It is on a mini jet engine card

author: amyk
author_rank: Super Contributor
timestamp: December 16, 2024, 10:46:36 am
content: MOSFETs of some type.

author: brkklcl
author_rank: Newbie
timestamp: December 16, 2024, 11:42:32 am
content: Yes, I guessed it too, but I can't figure out what kind of mosfet it is

author: u666sa
author_rank: Frequent Contributor
timestamp: December 16, 2024, 11:50:54 am
content: Connect to transistor tester and you will see what kind it is. For replacement use similar.

author: brkklcl
author_rank: Newbie
timestamp: December 16, 2024, 12:02:02 pm
content: I have this LCR-TC1 Tester. Can I do it with this, how should I connect it?

author: brkklcl
author_rank: Newbie
timestamp: December 22, 2024, 01:01:31 pm
content: With the help of my friend stowAway I found what the piece is. Thank you everyone
The power cable of Agilent 41802A INPUT ADAPTER - Page 1
Forum section: electronics / repair

author: wallacetan
author_rank: Newbie
timestamp: September 08, 2022, 07:25:51 am
content: Hello everyone, I got an Agilent 41802A INPUT ADAPTER with the power cable cut off by someone.I can't find the ADAPTER's service manual except for the user manual on the Internet.I know that its power supply is -12.6V, Ground, +15V.I teardown the Agilent 41802A and the power cable is three colored wires, yellow, brown and green.I can sure that the brown wire is the ground wire, but can't figure out which of the yellow and green wires is positive and which is negative.Anyone help me?

author: tooki
author_rank: Super Contributor
timestamp: September 08, 2022, 06:02:51 pm
content: Look up the part number of the IC, find its data sheet, and see which pins are the power supply pins. Then use a continuity tester to see which one connects to which wire. (My guess is that the IC is an op-amp or instrumentation amp, which is why both voltages are needed.)

author: wallacetan
author_rank: Newbie
timestamp: September 11, 2022, 08:12:03 am
content: Yes, I did. I teardown it completely.The other side of the board knows that the yellow of the power line is positive and the green is negative.I culdn't find the power connetor, I cut the cable from the other ADAPTER and made an extra extension cable.It can be used normally now.
The right tools to handle electronics equipments and components - Page 1
Forum section: electronics / repair

author: Jasonbit
author_rank: Regular Contributor
timestamp: January 05, 2022, 09:15:48 pm
content: Hi everyone,I need gloves, brush tool and wipes to cleaning boards and electronics components. All times I need clean something on the board I has with fear to kill any component with my static electricity or static electricity I could create with the brush tool, for example.I know the anti-static bracelet but I prefer isolate totally me from electronic components.On this video (https://youtu.be/swls2yukYjs?t=273) he used the wet wipe. Exist a specific wet wipe to do this job? Or any kind wet wipe could be use?Thanks

author: tooki
author_rank: Super Contributor
timestamp: January 05, 2022, 09:56:58 pm
content: Why do you think insulating yourself is better? For ESD safety, it’s absolutely the exact wrong thing to do. (Go look at how capacitors work: two conductors separated by an insulator. Being insulated is what allows you to build up a charge that can damage the part.)I haven’t seen any wipes marketed specifically as flux cleaning wipes, but basically you want a low-lint cloth. There are synthetic ones like shown in the video, or pure cellulose ones (like Kimwipes) that are just purer, low-lint Kleenex.

author: Squarewave
author_rank: Frequent Contributor
timestamp: January 05, 2022, 10:04:10 pm
content: Post in this sectionhttps://www.eevblog.com/forum/beginners/You'll find lots of useful information.

author: BrokenYugo
author_rank: Super Contributor
timestamp: January 05, 2022, 10:28:13 pm
content: ESD safety is all about getting everything to the same potential (earth is typically used for convenience) at a safe rate (hence the very high resistance ESD mat) and keeping it there. Isolation is exactly what you don't want to be doing.I found this presentation rather informative.

author: abdulbadii
author_rank: Frequent Contributor
timestamp: January 06, 2022, 05:03:24 am
content: ground your hand a minute or so each time before working upon them on top of (tiled) groundthat's it

author: tooki
author_rank: Super Contributor
timestamp: January 06, 2022, 03:20:21 pm
content: Quote from: abdulbadii on January 06, 2022, 05:03:24 amNo, that is far from it. Yes, 90% of the time it’ll probably be OK. But it is not a reliable method. Companies don’t spend thousands on ESD protection for fun.

author: m k
author_rank: Super Contributor
timestamp: January 08, 2022, 07:00:50 pm
content: Quote from: Jasonbit on January 05, 2022, 09:15:48 pmSilicone gloves?https://en.wikipedia.org/wiki/Triboelectric_effectMy empirical study says that walking is the worst and 2nd worst is departing from a chair.