hybridfree/eevblog-posts huggingface dataset:
Repaired Metcal Mx-500 with parts laying around - Page 1
Forum section: electronics / repair

author: jonsig
author_rank: Contributor
timestamp: December 27, 2021, 08:02:35 pm
content: Good day.Bought this metcal mx-500 older version from ebay, "not tested" . Ofc broken.. It was easy repair but i replaced the IRF530(Q4) withIRF540 , increasing RDSon from 20mOhm to 60-80mOhm100µF polyester 63V (C24) replaced with one of those monolithic ceramic capacitors from ebay (brown ones) "max" 50VZTX749 (Q1) => with 2SA966 lowering Ic 2A down to 1.5A(had to cross base - collector terminals on the to92)And the mx-500 is back to life, but i´m not sure how long it will last. How bad is the monolithic cap as replacement ? i ´m hoping the to-92 wil have little headroom thou Ic capability is lower. IRF540 should generate more heat if i remember the datasheet correctly.

author: 1audio
author_rank: Frequent Contributor
timestamp: December 28, 2021, 04:38:01 am
content: The cap may be stressed in that location. It has to pass some power and those monolythic caps change value with voltage, a lot. A good polyproplyene would be a better choice. The 2W 100 Ohm load suggests that there can be significant power so a cap rated for current may be required. ideally film and foil construction or an NPO/COG ceramic however that large and expensive for a .1U.

author: jonsig
author_rank: Contributor
timestamp: March 12, 2022, 11:32:23 am
content: Yes , replaced the c24 capacitor with film capacitor. And replaced the old thermal goo with arctic mx-4 thermal paste. I have no idea if the semiconductors gain anything from that because of large contact area.
Replaced neons in Fluke 845AR - Page 1
Forum section: electronics / repair

author: EE4all
author_rank: Regular Contributor
timestamp: January 08, 2024, 12:02:16 am
content: I obtained a broken Fluke 845AR, with wild meter swings. Upon opening and inspecting the neon chopper bulbs, they were a little dim, and blackened.I replaced them with some NE2U A3C tubes that were readily available locally. This alone has brought the meter back to life and now I can zero it, with around +- 50 nanovolt noise swings on the most sensistive 1 microvolt range. Is this about normal?Some further notes:I pulled the old tubes out and made a comparison of their behavior compared to the old ones. With a 30K resistor in series, and the room darkened, the new ones ignite around 12 volts lower (104v vs 116v) than the old ones and of course have clear glass. I also noted that originals lit up the entire electrode inside, whereas the new ones light only in the center. Therefore, I measured a small amount of extra height was needed to align this Illumination with the center of the glass tubes. Pictures of old and new attached.

author: EE4all
author_rank: Regular Contributor
timestamp: January 08, 2024, 12:05:59 am
content: Another note, it is good to check the tubes before installing them. I bought a box of 10, and the first one that I tested would ignite in one spot and then flicker down to another for the solid burn. I did not use that one. The next 2 out of the box stayed lit in the same spot that they ignited from, and I used those.

author: EE4all
author_rank: Regular Contributor
timestamp: January 08, 2024, 01:49:55 am
content: I noticed some older threads digging into the noise measurements and such. I will have a read, do some of my own tests and report back anything interesting.

author: enut11
author_rank: Super Contributor
timestamp: January 08, 2024, 07:03:13 am
content: There are also threads on the Forum somewhere replacing the neons with LEDs

author: EE4all
author_rank: Regular Contributor
timestamp: January 08, 2024, 08:47:06 pm
content: I found 3 capacitors in need of replacement at half their rated capacitance, and another few borderline, so today I just went ahead and ordered a full replacement set from Mouser. I was able to find good replacements in stock with high temperature, voltage, and capacitance ratings a bit above their specification, as the originals were all rated at the typical -10 to +50% specification as a lot of axial capacitors of the era were.I will come back to checking the noise and performance after the full recap.
Repaired Sony GTK-XB5 Daughterboard - after some advice  - Page 1
Forum section: electronics / repair

author: lukehicks
author_rank: Newbie
timestamp: January 05, 2025, 06:55:06 am
content: I picked up this speaker for free off marketplace, I found the power plug had been damaged and a surge protector next to it had also been moved.I removed and re-soldered the power plug, I also heated and straightened the surge protector next to it.The board has physical damage, cracks and bending. I straightened it as best I could (you can see the original damage from the photo I've attached).I've turned it on and everything seems to be working fine.Is this ok for a repair as it is on the power board ? I'm pretty new to this, I don't want to sell a speaker which is a potential danger.Thanks for your advice!

author: Swake
author_rank: Frequent Contributor
timestamp: January 05, 2025, 11:44:20 am
content: It seems it was physical to begin with. Difficult to asses the remaining damage.So the question is now, is it fragile or not and will it break again under normal use. The PCB traces can be doubled with wires soldered on them and the PCB itself can be re-enforced with epoxy.You should inform any buyer of the repair.

author: lukehicks
author_rank: Newbie
timestamp: January 05, 2025, 12:09:59 pm
content: Thanks for the reply!The board does seem fragile. Its fixed in place with 4 scews and 2 screws on the plug itself which helps strengthen the board. Ill add some epoxy over the damaged area, that seems like a good idea.I did scratch/expose some of the copper in the pcb when I resoldered the plug back on as the area was damaged.I had it on for a few hours everything seems to be working fine.Thanks for the advice!

author: lukehicks
author_rank: Newbie
timestamp: January 07, 2025, 10:39:42 am
content: Thanks for the advice, I covered the pcb damaged area top & bottom with a clear epoxy resin and the board is now significantly stronger.

author: Swake
author_rank: Frequent Contributor
timestamp: January 07, 2025, 11:09:28 am
content: I believe that was a good choice
'Repaired' subwoofer hums from TX - Page 1
Forum section: electronics / repair

author: scottb721
author_rank: Contributor
timestamp: February 22, 2023, 12:43:07 pm
content: I was given a huge Accusound HD Series 1 subwoofer that was dead. I opened it up and found a couple of bulging 6800uf caps. They were part of four so I replaced all four.Subwoofer now works great and I might actually swap it for my Martin Logan, however, when you're within a few feet and there's no input playing you can hear the transformer humming (driver is silent).Probably speaking nonsense here but I measured the 'noise' and it's peak was 150hz with harmonics 50hz either side.Anything I should try to fix the hum before just sticking it on a smart switch so it turns off when not needed ?Thanks
Repairing a Bicycle battery - Page 1
Forum section: electronics / repair

author: fant
author_rank: Contributor
timestamp: July 01, 2024, 02:57:53 pm
content: Good morning;I am trying to repair a BMS for a bicycle battery where a component is missing.Anybody has the same board so to know the characteristics of the component or at least a datasheet of the protecting IC (OZ7714CN)?The open voltage of the battery is 48V, but no power on output.Thank you in advance

author: Greybeard
author_rank: Frequent Contributor
timestamp: July 02, 2024, 12:12:45 pm
content: Datasheet:http://www.o2micro.com/products/O2%20807&G807C%20Product%20Catalog%202023-6-26(final).pdfProblem:Your IC is SOIC24, datasheet shows QFN28, so pin numbers are not matching.

author: fant
author_rank: Contributor
timestamp: July 02, 2024, 09:12:05 pm
content: Good morning;thank you for the link, but I had already seen it and discarded due to the pin count difference.I can find some spare on aliexpress, but before changing it, I would like to make some circuit investigation.Anyway, again thank you for the search and time spent.If anybody has new info, will be very appreciatedBest regards

author: indeterminate
author_rank: Regular Contributor
timestamp: July 03, 2024, 12:31:16 am
content: At a wild guess it will be the Bat 1 pin of the ic so the missing component will be another 100 ohm resister

author: fant
author_rank: Contributor
timestamp: July 03, 2024, 08:15:34 pm
content: Thank you "indeterminate".I did it, but it begun to heat up.Tested, the voltage difference between pins is 3,7 - 3,8 V (probably the firs element of the battery pack), so I've tried with a 0,1 uF and second test with a 1 nF capacitor, but no result.I am beginning to think that that it is locked into the anti-theft function, even if the battery belongs to a friend of mine and therefore I know that the origin is legal and he assured me that there is no switch or key on the battery for this function.Continuing to dig.Thanks to everybody

author: Greybeard
author_rank: Frequent Contributor
timestamp: July 04, 2024, 08:12:34 am
content: This photo may help you (arrow doesn't mean anything):https://electrotransport.ru/index.php?topic=5439.msg2302542#msg2302542I would not invest much time and energy to find the root cause of your problem, I'd just buy a new BMS PCB.

author: fant
author_rank: Contributor
timestamp: July 06, 2024, 04:23:44 pm
content: I made some more test, but no result.So, probably I will buy a new BMS.The deadline is Tuesday, If I will not fix it, I will change BMS.Thank you to everybody for the suggestions and help.Mandi
Repairing a gtx 770 from MSI with missing caps - Page 1
Forum section: electronics / repair

author: more_stars
author_rank: Regular Contributor
timestamp: July 21, 2020, 09:09:38 am
content: I was able to get a GTX 770 for cheap and so, it was broken, it would not give any picture on the screen so after taking a look at the board, I was able to see that there ware a lot of missing caps and rezistors. Those are from the ram modules and also from the main gpu. I took an old dead gpu and started to took components from one board and solder them to the other one. (If I needed a cap fir the ram, I was loking for the same size and same aproximate placing of the cap on the other board)Now, the board kind of works but not perfectly. It tooks 10 second for the board to boot up with an image, then, it will display the image but with a lot of little white lines on sectors so it may be because of the ram, eight?. After that, when the PC boots up, checking with gpu-z, I don't get all the info from the board and so, there are three fields that don't have any info on them: Memory size, Bandwidth and Bus speed.What may cause that?

author: more_stars
author_rank: Regular Contributor
timestamp: July 21, 2020, 08:54:28 pm
content: This is a photo with the output of rhe video card.

author: Rasz
author_rank: Super Contributor
timestamp: July 22, 2020, 02:45:43 am
content: what you want is MATShttps://drive.google.com/file/d/1qq5pzhWlpmtgNf8Q5KhCupwszhrQX3fY/view?usp=sharing

author: more_stars
author_rank: Regular Contributor
timestamp: July 22, 2020, 06:11:20 am
content: Sorry. What exactly is mats and how wxactky do I supose to use it.

author: Rasz
author_rank: Super Contributor
timestamp: July 22, 2020, 10:36:33 am
content: its a memory tester, part of MODS
Repairing a Keithley 197 - Page 1
Forum section: electronics / repair

author: Zachrey
author_rank: Newbie
timestamp: June 09, 2020, 12:44:52 am
content: Please help!I just got a Keithley 197A from a seller on eBay.com and it is clearly defective! The seller will not take a return so I may have to try and fix this bugger! I have a little bit of experience with this and only have an oscilloscope and a multimeter to work with. Here is a Youtube video of what the unit is doing. Do you think there is any hope?https://youtu.be/6OrLtb9O-coThanks!Zac

author: Wytnucls
author_rank: Super Contributor
timestamp: June 09, 2020, 08:27:08 am
content: Here is the maintenance manual with schematics:https://doc.xdevs.com/docs/Keithley/197/197_901_01A.pdf

author: tooki
author_rank: Super Contributor
timestamp: June 09, 2020, 04:04:42 pm
content: One thing to check is the FETs that perform the range switching.As for it switching to dB, that’s not a default for any mode, so perhaps there’s contamination on the display PCB, which the dB button lives on, causing it to detect a spurious press of the button. Give those contacts a clean. Oh yeah, and see if there’s any difference with the backlight on or off — the high voltage supply for the EL panel is also on that PCB. I don’t know if they have any failure mode that could cause noise, but it’s easy enough to test so why not!P.S. it’s not good form to hijack an existing thread for a new question, even if it’s about the same model. It’s better to start a new thread.

author: akabek
author_rank: Contributor
timestamp: February 02, 2021, 10:33:20 pm
content: Yesterday I received a Keithley 197a I purchased from ebay. I took a gamble as it was listed as parts and not working. Today I plugged it in and the screen was showing OL and the range buttons including auto would not lock in place after pressing a button. I found a couple of repair videos on You Tube that I reviewed. I took that cover off and removed all boards so I could look over the components. Everything seemed OK except the buttons would not stay in when pushed. I applied Deoxit 5 followed by Deoxit gold. I waited 15 minutes and reassembled it. I connected a DC power supply and tested a resister and it is working now. With the wierd things going on I would not have thought cleaning the controls would make that much of a difference but give it a go.

author: Ordinaryman1971
author_rank: Frequent Contributor
timestamp: February 03, 2021, 05:39:10 pm
content: I think it's a great advice, clean the switches first. Deoxit is great, exercise them after applying the Deoxit and try to take measurements again.

author: akabek
author_rank: Contributor
timestamp: February 03, 2021, 06:13:35 pm
content: My unit was doing a lot of weird stuff. After reviewing YT videos with similar oddities that were corrected with Deoxit I am a firm believer in the product. Right after doing a visual inspection of the components I would go right to cleaning and lubing switches and dials with Deoxit.
Repairing a Keithley 6517A Voltage Source Output - Need U303 (801A08) firmware - Page 1
Forum section: electronics / repair

author: RogerioHein
author_rank: Newbie
timestamp: July 16, 2025, 03:18:31 pm
content: Hello, there!My Keithley 6517A (firmware C05) is not allowing the voltage output source to be activated because it is energizing the three relays (K301, K305 and K306) from the U303. As a result, I can't measure the voltages at the test points (+/- 12V, +/- 120V, +/- 1200V), but they are there, and correct, if I use C330 ground pin as a reference instead of the black output binding post.I've copied the program installed on my U303 (attached) and it's apparently corrupted.Would any good soul have a working copy of the program (801A08) saved on the U303 to give me, please?Thank you very much.
Repairing a Krups Nespresso XN2120 water pump - Page 1
Forum section: electronics / repair

author: jimmyc_
author_rank: Contributor
timestamp: January 29, 2022, 02:51:49 am
content: Hi all,I've got a Krups Nespresso XN2120https://www.bean2cup.org/kaffeemaschinen/krups/626_nespresso_essenza_programm/water pump that stopped functioning. It's a Sysko water pump that runs on 230V. I've checked the inputs from the PCB to the Sysko water pump and found 198V was sent to the water pump, instead of 230V. I assume that's the reason why the water pump does not pump when the Make Coffee (either espresso or lungo) button was pressed.On the XN2120 PCB I've replaced the 680uF and 220uF capacitors. I've also tested the replacement capacitors before installing them.Any ideas?

author: Renate
author_rank: Super Contributor
timestamp: January 29, 2022, 02:51:09 pm
content: I don't know anything specifics, but I worked on an espresso machine once.The pump was a simple solenoid with a metal slug and two one-way valves.It was fed line voltage, but through a diode to make it more "pulsey" and to divide (what would be the double) frequency.So any DVM voltages on the coil would be a bit misleading, whatever they were.

author: Jeroen3
author_rank: Super Contributor
timestamp: January 29, 2022, 04:50:47 pm
content: Did you download the repair manual?Krups provides them with extremely detailed instructions and schematics for their machines.For example for my machine it states the pump has a thermal fuse, where the fix is "replace pump", because it is embedded in the pump (pump has 4 wires).

author: jimmyc_
author_rank: Contributor
timestamp: January 30, 2022, 02:36:10 am
content: Quote from: Renate on January 29, 2022, 02:51:09 pmOh! I didn't know anything about that pulsey pulse... This is new to me. Did it work for you using an analog mm?

author: jimmyc_
author_rank: Contributor
timestamp: January 30, 2022, 02:37:22 am
content: Quote from: Jeroen3 on January 29, 2022, 04:50:47 pmI've looked around and found only the user manual... Do you have a link to the service repair manual for the XN2120?

author: Renate
author_rank: Super Contributor
timestamp: January 30, 2022, 10:16:59 am
content: Well, if you've got no voltage then the diode is open or the control isn't sending anything. If it looks exactly like line voltage then the diode could be shorted. If the reading looks funny, it's probably ok. You can also try your meter on a high DC range XXX.X V and see if it's DC. (Don't go to a lower range if you're not seeing anything because it could be pure AC.) Or you could just check the diode.In my case, it was that from disuse the slug had gotten all gummed up. The pump core came all apart, but I forget how.
Repairing a Lavolta BPS-305 (Rebranded Longwei PS-303D-M) - Page 1
Forum section: electronics / repair

author: Hatsuwr
author_rank: Newbie
timestamp: May 09, 2024, 12:44:50 pm
content: Found this thing corroded, dirty, and dented. 30V/5A. Don't have a whole lot of experience with these things, but it's mostly working now. Voltage is spot on, current is touchy, waiting on a replacement switch. Main thing I know I'm still missing is a replacement center binding post. Needs to have a shaft ~26 mm long and 5 mm diameter.Input voltage selector was corroded and had high resistance, so I just removed the switch components and hardwired it for 120V. Also replaced the 20 AWG neutral wire with 16 AWG.The bridge rectifier gets well over 100 °C in normal operation, and got a lot hotter than that when the power supply was overdriven accidentally. Planning on replacing it with this:https://www.digikey.com/en/products/detail/micro-commercial-co/GBJ5006L-BP/16718585I think I'll keep it mounted on the chassis, since the replacement should run much cooler. I also removed the paint from the chassis at that ground point on the bottom right. I didn't check, but I highly doubt the case was grounded previously.This 4PD2 switch was causing some interesting problems. It is supposed to toggle between high and low current modes, the latter presumably reducing noise on the output. It was failing though, especially in the high position. This could cause the current reading on the display to be lower than it should be, sometimes just zero, but it would also increase the actual current well beyond what it should be - over 11A at one point before I shut it down. It has 4 mm pitch between pins, and 6 mm between the rows. This seems to be nearly an exact match:https://www.digikey.com/en/products/detail/c-k/F4UEE/417520There are a lot of oddities and unpopulated spaces on the board. My favorite is on the bottom left - the 3 hole spot for a potentiometer that is populated with a capacitor:
Repairing a NES transformer cable - Page 1
Forum section: electronics / repair

author: Moriambar
author_rank: Unknown
timestamp: December 06, 2021, 09:40:31 pm
content: Hi,I recently have been given an NES for repair by a friend. The first issue seems to be that the power cable from the transformer to the nes is broken (I heard it's a common issue).Being an incredible noob in repair I'm needing help in what to search for as a replacement cable (I live in Italy, perhaps it matters as per the cable 'types') and also what kind of barrel jack to solder and how (and also where to find it, are normal distributors as RS fine?)thanks for the help!

author: james_s
author_rank: Super Contributor
timestamp: December 07, 2021, 12:17:30 am
content: IIRC it's a standard 5.5/2.1mm barrel connector. The cable is not critical, you just want something fairly flexible that can carry 500mA or so without too much voltage drop. Can you tell where the break is? If it's near the end you may be able to just snip off the connector and install a new one.

author: Moriambar
author_rank: Unknown
timestamp: December 07, 2021, 08:31:36 am
content: Quote from: james_s on December 07, 2021, 12:17:30 amHello and thanks for your reply.EDIT: I found out that continuity was not a property of the original cable. I luckily found a "good enough" cable in my house and made a repair. Power seems restored.Thanks
Repairing a power supply for Lecroy WaveRunner 6051A : Wordpress Repair Guide - Page 1
Forum section: electronics / repair

author: lentaja.aurinkolasit
author_rank: Newbie
timestamp: September 18, 2025, 07:55:19 am
content: Hello everyone,I have completed the repair and documentation of a Lecroy Waverunner 6051A powersupply. If it can be of help to anyone.I created a wordpress website for the occasion. Here's the link:https://unfoldingcircuits.wordpress.com/2025/09/17/repairing-a-power-supply-for-lecroy-waverunner-6051a/Have a nice dayLA

author: Swake
author_rank: Frequent Contributor
timestamp: September 23, 2025, 09:07:39 am
content: Nice write up, thanks.

author: coromonadalix
author_rank: Super Contributor
timestamp: September 23, 2025, 11:42:48 am
content: no punbut i would save all in a pdf and put / attach it to your repair thread for keepsake
repairing a powersupply for Philips led tv.  Led driver problem. - Page 1
Forum section: electronics / repair

author: Tony.T
author_rank: Regular Contributor
timestamp: March 13, 2023, 11:35:30 am
content: Have a powersupply board.https://www.ebay.com/itm/404055262298If i connect the backlight to the PS...my lamp that i have in series for protection starts to pulsate 3-4 times after ps-on. (pfc ...which seems normal) , then the tv-led-backlight turns on and then off again after one second. The PSU restarts itself as soon as I turn on the backlight. (ps-on and bl-on +3.5V). Then it tries to turn on the backlight again and same behavoiur...it shuts down. There seems to be some problem that the current is to high and therefore the switching reboots. The tv has 2 ledstripes.. if i disconnect one of them...regardless of which one. The PSU starts and works and this ledbacklight is turned on. Now i can connect the second ledbacklight again (only two cables are for backlight)...the second one lights up and the PSU works. Is seems that there is a lot of current drawn at startup that makes the PSU to reboot.BUT...the thing here. My bulb...that i use for protection () ..glows. 20% at least from full glow. Normally the bulb lights up and then turns off when working with SMPS. If it is lit...there is a short circuit. But here it is glowing at 20%.Is this the same as partial short cut? Some component that are not 100% functional. That also causes the current limit to trigger when starting up but works if i disconnect one led and then connect it back again.is this partly glowing protection bulb normal? i think if the PFC circuit somehow affects it and that it is normal or do you think that there is something wrong with led.driver part of the circuit? All other things works fine. 8V standby....12V after ps-on .... 24V output from led driver. But as soon there is a load on the ledside...the shutdown occurs.Hope someone can just confirm or comment on this . Just for mee to be able to narrow it down a bit and not chasing things that maybee are not a problem. My opinion is that there is something partial shortcutting. Thanks,.

author: Tony.T
author_rank: Regular Contributor
timestamp: March 13, 2023, 08:21:50 pm
content: Yep...it was a partial shortage....one of the leddrivers IC;S that i have changed was shorted partially...
Repairing a Rocktron GAP v1 - Replacement fuse - Page 1
Forum section: electronics / repair

author: alderfc7
author_rank: Newbie
timestamp: August 19, 2024, 09:24:45 pm
content: Hi,I have been working on an old Guitar preamp Rocktron GAP v1 (model of 1990 I think). These had issues with the Voltage regulators and caps blowing due to heat since they are next to the transformer.I have replaced the regulators and caps and looks like the fuse is also blown. I need some help identifying the right resistible fuse to replace it with (It's the first time I encounter such fuse).As I understand this is a 500Ohm 1/2Watt fuse (the rating of the preamp is 22Watt which aligns with a 500Ohm resistor).Can I have some help confirming it and get maybe some suggestions on replacement options?Thank you in advance!

author: David_AVD
author_rank: Super Contributor
timestamp: August 20, 2024, 08:54:17 am
content: It's a 500mA fuse, not a resistor. The rating (1/2 Amp) is written on the PCB.

author: alderfc7
author_rank: Newbie
timestamp: August 20, 2024, 06:11:21 pm
content: thanks for the help!yeap, i can confirm it's a 500mA fuse. first time i come across.
Repairing a Small Home Space Heater Fan - Page 1
Forum section: electronics / repair

author: DW1961
author_rank: Frequent Contributor
timestamp: November 09, 2023, 03:03:34 am
content: I've had this for winter use in our bathroom for two seasons now. The fan is starting to chirp.It's just one of those Ceramic Small Heater with Thermostat, 750W/1500W box fans that sits on the floor.I was thinking about replacing the fan in it if it is cost effective, and I can find the right size fan and voltage. Does anyone know if they have 120V fans in them? Looking at it inside the case, it looks like a 120mm fan size and 25mm thick, similar to a computer fan in size.I'll need to take it apart to really know for sure, but I haven't done that yet.It's only 21 dollars, but I hate discarding "all of it" because a 3 dollar fan went bad." Just a damn waste of materials.

author: floobydust
author_rank: Super Contributor
timestamp: November 09, 2023, 03:38:50 am
content: Just take it apart and oil the fan's bearings.Always check for recalls on these things as well. It sure looks like one of these:Amazon Recalls AmazonBasics Ceramic Space Heaters Due to Fire and Burn Hazards (Recall Alert)"Amazon received 25 reports in the United States and 5 reports in Canada of the ceramic heater overheating, burning, or sparking. Two of those reports included minor damage to power outlets. There were no injuries associated with the incidents. No incidents were reported in Mexico."

author: amyk
author_rank: Super Contributor
timestamp: November 09, 2023, 05:27:00 am
content: Quote from: floobydust on November 09, 2023, 03:38:50 amWho wants to bet those were bad outlets with loose contacts in the first place?Space heaters are one of those loads which are pretty much guaranteed to draw their rated amperage at a 100% duty cycle. Those say PTC on them but I suspect something else is going on as true PTC heaters are intrinsically safe:

author: DW1961
author_rank: Frequent Contributor
timestamp: November 09, 2023, 05:52:40 pm
content: Quote from: floobydust on November 09, 2023, 03:38:50 amI'll have a look, but I'll bet they are sealed bearings.
Repairing a T2 Bluetooth Speaker  - Page 1
Forum section: electronics / repair

author: gg23
author_rank: Newbie
timestamp: June 01, 2020, 05:03:47 am
content: Hi all,Im new to the forum so I hope I am posting correctly.I have a T2 Bluetooth Speaker that looks like this:https://www.amazon.com/gp/product/B07RWSR3M7/The USB Micro B socket is damaged so it will not charge. Ive opened the unit and the socket sits on a single circuit board labelled as follows:SW_H_JL6925_T2_Main_V2i think it would be easier to replace the whole board as the USB socket would be very difficult to remove and replace.Any ideas if it is possible to replace the board and where I could purchase?Any advice greatly appreciatedGreg
Repairing a tire changing board. Combining transformers output - Page 1
Forum section: electronics / repair

author: Oxmstr
author_rank: Contributor
timestamp: February 16, 2024, 05:31:24 pm
content: I've got an "urgent" fix request of his tire changing machine main board. I couldn't find any pin compatible local transformers, and I don't know much about transformers. I didn't have the board till today and I'v ordered the transformer yesterday, didn't know that it's outputs are combined.My question, should I solder together pins 8 and 11 of the new transformer and wire it like the old one? The 0-115-230 V is no problem, just solder in the 0-230 V, but got no clue about the secondaries.

author: Jwillis
author_rank: Super Contributor
timestamp: February 16, 2024, 09:38:49 pm
content: Did they send a Datasheet with the transformer? I'm guessing that it's the one that can be downloaded here.https://alfaelektro.pl/produkt/tez-10d-2309-9v-transformator-zalewzywica.html#downloadIt shows the pin out of the TEZ10D 2X secondary. So combining 8and 11 will give 18V from pin 12 to pin 7. Pin 8 and 11 also become Centre tap 0V so between 7pin and 8+11pins makes 9v and pin 12 and 8+11pins makes 9V.

author: MarkT
author_rank: Frequent Contributor
timestamp: February 17, 2024, 10:09:45 am
content: Why did the transformer fail though? Without figuring that out there's a risk you replace it and the new one blows too because something has shorted and caused the original problem.

author: EHT
author_rank: Frequent Contributor
timestamp: February 17, 2024, 11:21:20 pm
content: Wait, how do you know the original has failed - what did you observe? (e.g. open circuit, short circuit, sign of heat damage). Its just a lump of iron and copper wire.. not likely to fail even if mistreated and as MarkT says, if it has failed then there is probably something else wrong
Repairing an Agilent U1065A digitizer card - Page 1
Forum section: electronics / repair

author: Trax
author_rank: Regular Contributor
timestamp: September 23, 2021, 06:53:12 am
content: Hi have in my lab a Agilent U1065A digitizer card which recently died,it does not produce any errors but it always measures junk,channel 1 is randomly fluctuating between 0 and 127, channels 2,3 and 4 show mostly 0 with the occasional skipe.Input does not mater... output looks always the same.There was no identifiable event that would be suspected to have broken it, it was working we put it in storage for half a year or so than we wanted to use it again and it did not want to.I already talked to a Agilent representative in my area but the card is to old for an official repair,so first is there anyone here with experience with diagnosing such equipment and could help me to find out whats broken and if its even repairableand or second: are there any 3rd party services that would repair such a card for a reasonable price?CheersTrax

author: Kleinstein
author_rank: Super Contributor
timestamp: September 23, 2021, 10:56:29 am
content: The 4 channels are to a large part seprate. A failure that effects all 4 channels could be something like a supply problem. So the point to check are the supplies and maybe clock. If there is really somerthing broken in the actual amplifier or ADC part, it is likely a lost case, at leat for the effected channel, as these are kind of custom / old parts that are likely hard to get.
Repairing an AKG 414 mic with NLA FET - Page 1
Forum section: electronics / repair

author: mkiijam
author_rank: Regular Contributor
timestamp: July 03, 2025, 11:35:14 pm
content: I'm trying to replace T1 SK30 with a 2n5457 which supposedly is an okay sub? The drain and source resistors need to change, but I am completely lost as to how to make it work or what values I need to put in there. Right now I have installed the 2N5457 and it seems to work, but the gain seems low. I have 2.5V on the drain and the source which makes me think that it isn't doing much?

author: Jeff eelcr
author_rank: Frequent Contributor
timestamp: July 03, 2025, 11:59:07 pm
content: 2SK30A replacement part. Still available. Look for gain group "R".Jeff

author: mkiijam
author_rank: Regular Contributor
timestamp: July 04, 2025, 12:50:46 am
content: Not too sure about that... I believe there are a lot of counterfeits, but original?

author: floobydust
author_rank: Super Contributor
timestamp: July 04, 2025, 01:14:35 am
content: I think the voltage readings indicate IDSSfor the replacement JFET is just too high. Pinout is different too. Don't trust a stompbox forum for such info lol.2N5457 IDSS1-5mA2SK30A(R) IDSS0.3-0.75mA (the part's last letter gives a range i.e. R: 0.3-0.75mA, O: 0.6-1.4mA, Y: 1.2-3mA, GR: 2.6-6.5mA).Replacement I would consider:J201IDSS0.2-1mA andJ/SST201 SeriesThere are other specs to consider Cissas well for selecting a JFET for condenser mic use. TIJFE150has very high Ciss24pF, too much would not use.2SK596 is super common but a bit too low current.Linear Systemsmanufactures replacements for old JFETs but use different prefixes like LSK. Use the root part number.Interfet.Both at Mouser and Digi-Key has some. Can be expensive.Aliexpress JFETs are rarely in spec and sometimes seem to be a different part altogether.

author: mkiijam
author_rank: Regular Contributor
timestamp: July 04, 2025, 04:40:18 am
content: Here is a comment from a world renowned mic guru "I would (and have) use(d) a 2N3819, a in U87. Same function, just needs to be properly biased." Any thoughts about this?
Repairing an old IBM Laptop Power Adapter - Page 1
Forum section: electronics / repair

author: jaxbird
author_rank: Frequent Contributor
timestamp: June 05, 2020, 04:25:59 am
content: My old IBM power adapter stopped working and I have a go at getting it up and running again:

author: Gyro
author_rank: Super Contributor
timestamp: June 05, 2020, 09:22:52 am
content: Nice explanation that therearealternatives to just stuffing mains into an SMPS to test it!

author: z01z
author_rank: Regular Contributor
timestamp: June 05, 2020, 11:29:06 am
content: Great tip for troubleshooting, thanks!One comment though, in an educational video it might not be the best idea to start touching the board, without discharging the mains capacitor. You know what you are doing and probably took precaution, but someone inexperienced might get the wrong idea.
Repairing an RS PSU knob - Page 1
Forum section: electronics / repair

author: sylvanoMTL
author_rank: Contributor
timestamp: March 06, 2025, 02:29:02 pm
content: I am repairing this PSU, that has a faultty voltage knob: the tactile press is not functionning anymore.https://uk.rs-online.com/web/p/bench-power-supplies/1757367?cm_mmc=UK-PLA-DS3A-_-google-_-CSS_UK_EN_PMAX_RS+PRO-_--_-1757367&matchtype=&&gad_source=1&gclid=CjwKCAiArKW-BhAzEiwAZhWsIK5Th_SlQ08oj8b5eqNNSH1Htb3CskMJi1Ve5HCuduNXpbq18HzUeBoCDrQQAvD_BwE&gclsrc=aw.dsI was able to disassemble the front panel, but the rotary/tactile switch has no reference. I took a picture of it. Does anyone would be able to provide some information, replacement part?I might be able to take more pictures on Monday if neededMany thanks

author: benj38
author_rank: Frequent Contributor
timestamp: March 06, 2025, 02:34:43 pm
content: Before looking for a replacement, maybe you want to try and fix this part instead. If you remove it from the PCB, you can easily "unfold", using a small flat screwdriver, the four metal tabs that hold its two major parts together.

author: Ian.M
author_rank: Super Contributor
timestamp: March 06, 2025, 03:30:38 pm
content: Get better pictures, inline with its shaft and from the back of the board, with a ruler next to it for scale, and use a DMM to find out whether its a quadrature encoder or a potentiometer. Miniature mechanical quadrature encoders with a push switch are a common commodity part, so you may just be lucky!

author: inse
author_rank: Super Contributor
timestamp: March 06, 2025, 04:23:30 pm
content: If it’s still ‘clicking‘ there is a chance it’s only a matter of dirty/oxidized contact.Then you could unsolder and cautiously disassemble it.If the contact spring is bent or the shaft deformed, you need to replace the encoder.
Repairing Anko AO8606 air fryer. - Page 1
Forum section: electronics / repair

author: LeWidget
author_rank: Regular Contributor
timestamp: March 17, 2022, 09:22:44 am
content: Hi all,We have an ANKO AO8606 air fryer that suddenly no power. I pulled it apart and probed the AC-IN, but wasn't getting voltage (or continuity from the plug to the PCB in the air fryer).I dug further and found a thermal fuse in the middle. No continuity on the fuse (but continuity on the plug > fuse, and fuse > pcb. but no beep on the fuse itself.)Now looking to buy a replacement fuse and heat-resistance sleeve to see if that fixes things.Anyone know if this fuse will be ok?https://www.ebay.com.au/itm/184832449980?hash=item2b08df5dbc:g:zaYAAOSw7I9hK0S5^ I can get 3x fuses (couple of spares) for $7, otherwise cheapest I've seen is 1x for $7.50 (Australian dollar)Also, the heat resistant sleeve. Are these ok,https://www.jaycar.com.au/high-temperature-basalt-fibre-sleeving-6mm-x-1m/p/WS5511?pos=1&queryId=d4b73cc6941c60e66a64f279c5f98d68&sort=relevancehttps://www.ebay.com.au/itm/324922546709?hash=item4ba6e49a15:g:ks0AAOSw6i1hsaA-

author: FIXITNOW2003
author_rank: Regular Contributor
timestamp: March 17, 2022, 12:18:48 pm
content: the thermal fuse in link should be ok as they do the 172 deg version you needthe sleeve is good to 200 deg so should also be ok

author: LeWidget
author_rank: Regular Contributor
timestamp: March 17, 2022, 01:01:47 pm
content: Thanks FixitQuote from: FIXITNOW2003 on March 17, 2022, 12:18:48 pmI might order a couple of them then, so I have a spare just in case. I didn't check, but do these fuses go in a certain way, or can they be installed in either way (like normal fuses) ?There was another sleeve too that I link but link seems broken. Would the one from Jaycar be better?https://www.jaycar.com.au/high-temperature-basalt-fibre-sleeving-6mm-x-1m/p/WS5511?pos=1&queryId=d4b73cc6941c60e66a64f279c5f98d68&sort=relevance

author: FIXITNOW2003
author_rank: Regular Contributor
timestamp: March 18, 2022, 07:50:58 am
content: Jaycar better as higher tempfuse either way should be ok ,but if you want and they look the same just do same way as original
Repairing APC UPS - sourcing obsolete chip - Page 1
Forum section: electronics / repair

author: PaulAm
author_rank: Frequent Contributor
timestamp: December 19, 2018, 12:00:15 pm
content: I had a small UPS that I put in place to backup my wireless modem. A couple of weeks ago it died with the overload light turned on. I just bought a battery for this thing, so it was worth opening up for a look.On the battery charging circuit two things were immediately obvious: a large electrolytic was leaking and the switching power IC had blown itself to pieces. Fortunately, it had blown the entire top of the IC so the number was still visible. Unfortunately it was a TNY255g which is listed as obsolete by Mouser and Digikey. The only source I could find was through ebay either in China or Hong Kong. After looking through the listings and reviews, I picked some from a vendor called Chipsgate. Six for USD $4.70 + 3 s/h seemed worth a risk. I figured on a 40% chance that I would get something that worked. However, the vendor offered a 60 day warranty and they seemed professional, so what the heck.They showed up the other day, I installed a chip and replacement cap and now I have a working UPS.It's only one data point, but I would try Chipsgate again if the need arose. Anyone else have experience with them?

author: t1d
author_rank: Super Contributor
timestamp: December 19, 2018, 05:03:58 pm
content: Given the value of the unit and the narrow parts supply chain, I can see taking the risk on a China IC that might be a counterfeit. Other options include sourcing a compatible part. Go back to the Mouser site and look up the obsolete part. Sometimes there is a similar part look up feature. Try that. Download the data sheet and match up specs, to something else, too. Got pictures?

author: PaulAm
author_rank: Frequent Contributor
timestamp: December 19, 2018, 11:40:14 pm
content: Well heck, the tny255gn-tl is available from Mouser for around $2. For some reason that didn't show up during my initial search.The G version was not RoHS.Oh well, it's still working now. If it blows up again I'll go back to Mouser.

author: MadTux
author_rank: Frequent Contributor
timestamp: February 15, 2020, 09:32:08 pm
content: Stay away from ebay chipsgate (Fengye Chen), got fake shit from them the 2th time by now.A batch of supposed GAL22V10, of which only about 40% are programmable and some relabeled power mosfets, with double RDS(on) of the real devices, for which I needed replacement.That scammer probably picks up whatever crap is available on Shenzhen markets for cheap and happily relabels it to whatever he wants as long as the specs are vaguely similar to the real thing, so the dumb buyer doesn't spot it immediately.Don't worry, btw, I'll get my money back, time is still lost, though
Repairing blown inputs on an Anritsu MS420K VNA (lost beginner)  - Page 1
Forum section: electronics / repair

author: cincin
author_rank: Regular Contributor
timestamp: August 26, 2024, 04:10:33 am
content: I have a sweet Anritsu MS420K Network Analyzer that has, I suspect, blown inputs on both channels.I cannot find a service manual or schematics for this unit, and Anritsu no longer has them either. If you know where I might find them, please let me know.I popped it open, and I'm trying to get an idea of where the problem might be. The fuses are good, unfortunately, I wish it had been that simple hehe.Both input modules are the same in the front section, and so far the damage appears to be identical in both circuits.At the very front, near the input jacks, there's a diode and 4 relays, segregated by a ground plane, that lead to a post connected to a signal wire (top right in the photo). I'm assuming this is the signal leaving the front section. However, the post is shorted to ground. And, the input BNC jack's center pin doesn't have continuity to the diode (top left in the photo), or to the post (top right). So I'm a little confused.I was suspecting one of the relays may be damaged or stuck to ground, so I disconnected the post from the wire coming out of the front section, but to my increasing confusion the 4 relays and diode are not what's shorted to ground, the wire that connects to the post is. So the short to ground is downstream from there? Yet there's still a problem with something here since the signal doesn't make it through to the post. Or are the relays supposed to be keeping the input jacks disconnected when the unit is off?This is all based on the assumption that the post in question IS the signal path, and not actually that circuit's ground. I'm assuming that to be the case because the post and wire connection are carefully isolated from that unit's chassis, which it currently has continuity to. But I am a beginner, and I suppose this could be a ground connection, and it is isolated from the chassis at that point so as to maintain a single path to ground. Especially since there's no continuity between the input port center pin and the post, or the input port center pin and ground.Schematics (or, you know, experience, or actual knowledge) would make all of this so much simpler...I'm hoping someone here with more experience with VNAs can shed a little light on all of this, or kick me in the right direction.I'd really love to get that unit going.Thanks!
Repairing broken silver ink traces on a mombrane keyboard - Page 1
Forum section: electronics / repair

author: ciccio
author_rank: Frequent Contributor
timestamp: July 20, 2020, 06:53:05 am
content: I' trying to repair the keyboard of an industrial controller.It's one of those keyboard made with domes fitted between two flexible circuits with printed silver ink cpnductive tracks.One of the tracks seem interrupted.Does somebody knows how to repair the tracks?I've seen that the adesive is stronger than the ink, so separating the two layers result in broken tracks ..Any idea?Best regards

author: Whales
author_rank: Super Contributor
timestamp: July 20, 2020, 07:07:00 am
content: Conductive epoxy, I've used it for exactly this purpose. Typically silver bearing. You only need a tiny amount.I got mine from eBay. General cautions:mine arrived in the form of syringes + hypodermic needles. Standard postNot what I was expecting and probably not safe to post like that.Difficult to use more than once or twice, epoxy sets in the needle/outlet.(Next time I'm checking how they send it before buying)

author: edpalmer42
author_rank: Super Contributor
timestamp: July 20, 2020, 07:53:11 am
content: Our cars have copper traces across the rear window to melt ice or frost in the winter. At the auto parts store you can buy repair kits that consist of a liquid that you use to paint across a gap in one of the traces. I've used that kit to repair a keyboard where one of the traces just disappeared.
Repairing broken turns on an AC motor winding - Page 1
Forum section: electronics / repair

author: Saco
author_rank: Contributor
timestamp: February 18, 2023, 11:29:10 am
content: Hello, my question is twofold so I didn't know exactly to type on the subject and whether to post it here or on the Beginners section but here's my situation:My de-humidifier's fan stopped working so I set on a journey to fix it. I immediately found out that the start capacitor was bad and since I didn't have a proper replacement at hand, tried one with a higher capacitance. Low and behold, the thermal fuse blew.The fuse is inside the motor's enclosure so I had to take it apart and while doing so broke off 5 turns of the winding.1 - Since it's only 5 turns out of a 1000+ turns winding I was considering just shorting them all together, but then realized, worst case scenario I could be actually shorting the entire winding in case I was unlucky enough to break off the first and the last turns. Am I correct?2 - As hard as it may be given how thin and short the tips are, I'm trying to solder the broken turns. As I understand it, I have to determine which ends correspond to the "start", "middle" and "end" sections and can solder them together in whichever order as long as the "start" and "end" are not solder together. Am I still correct?

author: WattsThat
author_rank: Frequent Contributor
timestamp: February 18, 2023, 03:52:08 pm
content: Yes, you cannot reconnect without first identifying where it starts and where it ends, otherwise you’ll short turns, which would be bad. I think this is what you’re proposing but I’ll repeat the way I see things:Identify the “middle” isolated, individual loops and then the ends that represent the start and end turns connected to the supply. The starting turn will be on one side of the break, the finishing turn must be on the opposite side. Move the start/end turns to the side.Connect remaining isolated loops in series, order not important and you’ll be left with two tag ends that then connect to the start/end turns.Don’t be afraid to separate the turns, peeling them away from the varnish dip and cutting lacing if you have to. Use short jumpers inside small heat-shrink. Difficulty depends upon where the break is, closer to the slots will increase your pain. In the middle of an end turn, well, that’s the best you can hope for.