hybridfree/eevblog-posts huggingface dataset:
BK Precision 8500 Repair Attempt - Doesn't draw current - Page 1
Forum section: electronics / repair

author: Shay
author_rank: Regular Contributor
timestamp: August 26, 2023, 10:05:24 am
content: Hello,I am trying to repair a BK Precision 8500 DC electronic load.The load powers up just fine and passes a self-test; it measures the correct input voltage. I am able to access the menu and set any mode I'd like without any issues.However, as I set up CC mode or any mode, choose any current, and click on the ON/OFF button, the unit just does not draw any current at all.I tried resetting the config in the menu to default, and I just couldn't get the unit to draw any current.Upon further investigation, here is what I have come up with so far:The control loop for the mosfets is working well.The supply voltages are good.I am able to make the unit draw current and show the drawn current only when I move the encoder constantly. Otherwise, it just sits at 0A.Upon testing the DAC (https://www.ti.com/lit/ds/symlink/dac7631.pdf), I've noticed it does produce output voltage when playing the encoder fast, which means the DAC is probably working OK and the control loop for the mosfets is fine.Probing the SDI pin (serial data input) on the DAC shows that there is some communcation and there is a CLK signal on the CLK pin. However, on the CC/CV Mode I only get those pulses of communcation when rotating the encoder fast. on the CW/CR I constantly get bursts of data, but no current at all (no output on the DAC)Could it be a faulty DAC?I would appreciate any help in investigating the problem.Shay.

author: Swake
author_rank: Frequent Contributor
timestamp: August 28, 2023, 05:55:46 am
content: Is there only one DAC? If so, is it used for the input voltage too, because then it is working.You might have a look a the remote sense inputs. Potentially there is some fault here.Would there be some external input/trigger required? This machine can likely be commanded with signals on the back.

author: Swake
author_rank: Frequent Contributor
timestamp: August 28, 2023, 06:03:38 am
content: There is a short FAQ in the manual with a question about your situation. They suggest to verify some specific settings.https://bkpmedia.s3.amazonaws.com/downloads/manuals/en-us/85xx_manual.pdfPage 73

author: Shay
author_rank: Regular Contributor
timestamp: September 02, 2023, 10:03:22 pm
content: And as always.. when repairing something, do the easiest thing first. No, its not measuring the PSU rails.. it's reading the manual.Thanks @Swake, that was the issue. Although I tried resetting the config settings, its not related to the "system" settings.
BK Precision 9129B Serial - Page 1
Forum section: electronics / repair

author: jgrossman
author_rank: Regular Contributor
timestamp: April 08, 2024, 09:59:31 pm
content: note: throughout, "not working" means "I can see UART on the scope, but no response from the unit"Hey eevblog forum, I recently acquired a used BK Precision 9129B power supply. I am trying to use the serial interface. Neither I nor the seller knows if the interface was working at the time of purchase. I was trying to use the DB9 connector with a USB-RS232 bridge but missed the probably 5 warnings that the DB9 is a TTL level interface, not a standard RS232 level (nice prank, BK. This is my error, but who does this???)I quickly realized the mistake and fashioned an FTDI serial to USB converter to try instead, but that did not work either. I sucked it up and bought the original IT-E312B adapter, thinking there may be some special sauce I was missing since it never actually states in the documentation that you can actually use anything else. No dice on that either, and cracking it open I didnt see anything special, just a PL2303TA serial-USB bridge and an isolator.I'm starting to suspect I have (unsurprisingly) damaged something while trying to use the USB-RS232 bridge. Buzzing out the DB9 comm. pins, they are in series with a 10 Ohm resistor, then straight into an STM32... great. I installed the debug header and dumped the contents of the STM32, but before I just go for broke and replace the STM32, I was hoping somebody could either point me towards a service manual or advise some additional troubleshooting I can do to narrow down where the issueactuallyis.Has anybody actually used the serial interface on this? The manual says that the display will show "RMT" when successful connection is made over the serial, but I have no idea how it can even determine that, since it supposedly does not have flow control (or at least, the manual claims so)

author: jchw4
author_rank: Regular Contributor
timestamp: April 09, 2024, 10:00:06 am
content: I had never have any experience with this particular model but earlier BK power supplies of the same class suggested using IT-E131 USB to RS-232 cable. If you google it you will find that it is ISOLATED conveter.This was important because connecting anything to RS-232 effectively made the first channel USB-referenced.IT-E131 is not explicitly marked isolated but I would not be surprised that it is in fact isolated.> DB9 is a TTL level interface, not a standard RS232 level (nice prank, BK. This is my error, but who does this???)I think it is reasonable to assume that modern "RS-232" ports are always TTL.
BK Precision 9130 Triple Power Supply resistor values for repair - Page 1
Forum section: electronics / repair

author: ahebert
author_rank: Newbie
timestamp: January 28, 2023, 06:20:55 am
content: I have a BK Precision 9130 that I hooked up backwards to a batteryand now I a want to replace the burnt parts, but I'm having trouble identifying one resistor value on the main analog board. Labeled #3 in the picture below, does anyone know the correct value?In another post (https://www.eevblog.com/forum/repair/bk-precision-9130-triple-power-supply-(identify-component)/msg3750955/#msg3750955), @jchw4 posted the following picture of the same board from the top view, but I cannot read the resistor colors from that view.Does anyone have a schematic?Or photo of a resistor where the color codes can be seen?Or other suggestions?Any help is much appreciated.

author: jchw4
author_rank: Regular Contributor
timestamp: February 03, 2023, 12:08:17 pm
content: Sorry for missing your post, I was away from the forum for a few daysI don't have specific photos of these resistors, but I attached a few that you could use as a reference. I was focusing on the MOSFETs and rectifiers, so resistors are a bit blurry.Let me know if you need more. I stuill have it, but disassembly was a bit painful as I remember

author: jchw4
author_rank: Regular Contributor
timestamp: February 03, 2023, 12:13:13 pm
content: BTW, could you take a photo of the main IC like I did here:https://www.eevblog.com/forum/repair/bk-precision-9130-triple-power-supply-(identify-component)/msg3745804/#msg3745804?It would be useful to get more photos and finally identify it

author: ahebert
author_rank: Newbie
timestamp: February 04, 2023, 10:12:16 pm
content: Awesome! Thank you so much! Looks like my resistor #3 is 1-ohm, based on your picture. Now I can order the parts and try the repair.I'll take a pic of the main IC from my unit and post it later tonight.

author: ahebert
author_rank: Newbie
timestamp: February 05, 2023, 03:00:23 am
content: I managed to get a clear shot of the IC, and this one isn't obscured as thoroughly. See attached.Looks to be an SST89E516RD2https://ww1.microchip.com/downloads/en/DeviceDoc/25093B.pdf.The markings on the bottom-left of your IC photo look distinctly different than this chip. I suspect they are different parts, but since this is an 8051-compatible MCU, I'm guessing that there are a bunch of interchangeable models from different manufacturers.

author: jchw4
author_rank: Regular Contributor
timestamp: February 05, 2023, 05:37:17 am
content: Quote from: ahebert on February 04, 2023, 10:12:16 pm"Brown" "Grey" "Black" "Black" "Brown" - seems more like 180 Ohm to me.You are probably right, it looks more like "Silver"

author: jchw4
author_rank: Regular Contributor
timestamp: February 05, 2023, 05:37:56 am
content: Quote from: ahebert on February 05, 2023, 03:00:23 amThank you very mich! This is interesting.
B&K Precision Model 1431 - Page 1
Forum section: electronics / repair

author: DJ_1898
author_rank: Newbie
timestamp: December 16, 2023, 10:07:22 pm
content: Just recently bought this scope off of eBay for a good price and was wondering if anyone has/knows where to get a service manual for it? I have searched this forum and many posted websites and could not locate this scope. Thanks!

author: BlownUpCapacitor
author_rank: Frequent Contributor
timestamp: December 17, 2023, 10:14:37 pm
content: I can't find a service manual either. But I don't think you need one. Looks like you have AC noise on your trace, This is usually attributed to bad AC line filter caps.Also here's a very general flow chart I have created in 5 minutes for power supplies.
BK9801 AC Power Source - Page 1
Forum section: electronics / repair

author: svcguy
author_rank: Newbie
timestamp: June 05, 2025, 04:18:00 pm
content: Hey all,Long time lurker, first time poster! I happened to come across a BK9801 for repair and snatched it up. Symptom is no power at all. Started simple and followed the AC input and found an open on the primary of the first transformer it hits. Primary side has 3 wires coming off - red, black, white. Red<->black is open as well as red<->white. Black<->white reads about 44ohm. This of course may not be the only issue but wondering if anyone knows of a replacement for this guy. There is a sticker that says P/N 101742, but Google turns up nothing. I did email ITECH's support (I believe they OEM this for B&K) but not holding out hope.

author: coromonadalix
author_rank: Super Contributor
timestamp: June 06, 2025, 10:26:10 am
content: have you asked BK directly they can sometimes be of good help

author: ITECH Izabel
author_rank: Newbie
timestamp: July 08, 2025, 02:14:21 am
content: You may contact BK for service directly,good luck if it is still under warranty.

author: Kean
author_rank: Unknown
timestamp: July 08, 2025, 12:20:42 pm
content: I have a working IT7321 which I think is pretty similar if not identical.So if you don't get any useful response from ITECH or BK then I could maybe open it up and take some measurements.I'm not likely to have time in the next couple of weeks, and my unit is for 230V AC supply if that makes any difference.
Black and Decker 20V DC Lithium Sweeper Circuit Board Repair - Help. - Page 1
Forum section: electronics / repair

author: cajoromi
author_rank: Newbie
timestamp: July 26, 2019, 05:06:21 pm
content: Hi,my leaf blower stopped working and upon taking it apart I discovered burn marks on the circuit board. The marks were around what appears to be two solder dots as outlined in the photo's I've attached.Can anybody please help to identify this specific part and tell me, if possible, how to repair it? My electrical knowledge is limited but I'll do my best to assist with any inquiries.Sorry in advance for the quality of the pictures.Any instructions or suggestions would be greatly appreciated.

author: rvalente
author_rank: Frequent Contributor
timestamp: July 26, 2019, 07:23:14 pm
content: Try to take better pictures, these a blury.

author: cajoromi
author_rank: Newbie
timestamp: July 26, 2019, 07:31:32 pm
content: I posted on another forum and was able to find a solution. Thanks, anyway.
Black and white CCTV monitor loss of V sync - Page 1
Forum section: electronics / repair

author: aberco
author_rank: Contributor
timestamp: September 15, 2023, 11:49:05 am
content: Hello all,I have a pair of video monitors, no name brand, which I have purchased to use on my Apple 1 build. They are both PAL, since I'm in Europe, and they work with the Apple1 NTSC output.Monitors both showed issues that I thought were coming from my Apple 1 build, as I had horizontal (pixel clock) jitter on the video signal. This jitter is dependent over what the computer is doing, it's not visible when the CPU does nothing (held in reset) but it is quite visible when running a program. Then I tried 3 other monitors from friends, CCTV monitors and vintage TVs, and none of them are showing the jitter, which had made me think that the issue was coming from my monitors instead.I can live with the jitter issue, but I tried to replace the electrolytic capacitors in one of them to potentially solve it and it now does not lock on V sync. The V sync adjustment pot makes the image scroll up or down and is very sensitive, I can get it sometime to stop scrolling but the start position can be anywhere on the display, not necessarily in the upper left where the image should start.The inside shows what is probably a very typical 1980/1990 CRT circuit using a TDA1170 for vertical and a TBA920 for horizontal drivers. I do not have the schematics, but it seems that they have followed the reference design for the TDA1170 and TBA920. I have attached a photo of the inside of the monitor.I'd appreciate any lead that would allow me to recover the lock on the V sync. Thanks in advance for the time!

author: Psi
author_rank: Super Contributor
timestamp: September 15, 2023, 11:54:07 am
content: QuoteThis seems somewhat contradictive.

author: BrokenYugo
author_rank: Super Contributor
timestamp: September 15, 2023, 02:29:55 pm
content: As I recall, monochrome NTSC/PAL50 are close enough they're sorta interchangeable IF you can get the vertical to lock on the display in question.

author: aberco
author_rank: Contributor
timestamp: September 15, 2023, 05:47:05 pm
content: Most PAL monitors will indeed work with NTSC signals, the color information is not needed. Then it's a 60Hz scan instead of 50Hz, but as said above it is fine if the monitor can lock on that V sync frequency. Many old monitors do.Maybe changing the capacitors did improve the tolerance in a way that prevent the monitor to lock onto the signal? as of now the V sync oscillator is free running. The TDA1170 receive the sync signal on pin 8, I checked with an oscilloscope and it is there and looking fine.
Black & Decker charger - Page 1
Forum section: electronics / repair

author: Dasypus
author_rank: Contributor
timestamp: August 13, 2022, 01:12:50 pm
content: Hi. I left my BDC2 36v battery charger charging the battery and noticed after a while the Green LED was no longer lit. The battery was fully charged. On opening the charger I found that the 3.15A input fuse had blown, so got another and replaced it. Now the fuse does not blow, but the LED does not light when the battery is inserted, as expected. I am not an expert in electronics, and being very careful, noticing some 340V DC and AC being stepped down to around 42V which (I think) is the charging voltage for the BL20362 battery, and this appears at the battery charging terminals. There is a PIC16F microcontroller on what appears to be LV side, but no DC voltages anywhere. There are no visible signs of damage that I can see, including inside the battery itself (apart from a burning smell on my fingers after battery disassembly, but this may be due to overheating?). I still can't tell if the charger is at fault, or the battery. Does the LV side of the circuit get its power from the battery, I know that may sound silly, but it would explain why the LED does nothing until one is plugged in, or did when it was working). I want to avoid messing too much inside due to the nasty voltages present (everything is also 115V above ground, double insulated device, etc...). There is also a TOP264-271 power supply chip, and the HV circuit roughly follows the example given in its data sheet to the point where the 42V exists after a twin diode rectifier, and that's as far as my limited knowledge goes... Regards.

author: Dasypus
author_rank: Contributor
timestamp: June 21, 2025, 01:27:52 pm
content: Wow, posted this ages ago, got no replies whatsoever. Anyways, I took a chance and bought a replacement (non B&D) half the price charger, been going well since. Shame I threw the original in the dumpster when I had to move home, would love to have had a go at finding at least why it failed. Be well.
Black goo on solder points - how to remove? - Page 1
Forum section: electronics / repair

author: ledshok
author_rank: Newbie
timestamp: February 09, 2021, 05:38:59 am
content: My son's Logitech G332 gaming headset had its cable chewed through by our cat so I thought I'd have a crack at replacing the cable.When I look at the PCB that the cable is soldered to, the solder points seem to be covered in some sort of black goo:Any idea what it is and (most importantly) how I could remove it so I can solder a new cable in?Thanks

author: ImABeginner
author_rank: Contributor
timestamp: February 09, 2021, 06:13:28 am
content: snot epoxy. Acetone does an OK job, but will also strip other plastic.

author: ledshok
author_rank: Newbie
timestamp: February 09, 2021, 07:09:11 am
content: Quote from: ImABeginner on February 09, 2021, 06:13:28 amThanks for that!This may be a dumb question, but if (aside from the epoxy) the acetone only touches the PCB and solder points - wouldn't that be okay?

author: jpanhalt
author_rank: Super Contributor
timestamp: February 09, 2021, 07:17:41 am
content: Is the goo hard or somewhat soft like hot melt glue?If it is flexible like hot melt, try isopropyl alcohol. I have best results with 91%, but 70% may also work. Wick a little on, and hot melt releases. It does not noticeably dissolve hot melt, so there is no residue to clean up.As for the PCB and other components, they are not affected by isopropyl alcohol and most likely not affected by acetone. Acetone is more aggressive and will affect plastics like ABS and styrene.

author: ledshok
author_rank: Newbie
timestamp: February 09, 2021, 07:48:58 am
content: There is some 'give' to it if I push a flathead screwdriver into it.If I only have access to 100%, would that be okay?

author: ledshok
author_rank: Newbie
timestamp: February 09, 2021, 08:10:51 am
content: Wow, it's working really well!Thanks heaps for your help!

author: S. Petrukhin
author_rank: Super Contributor
timestamp: February 11, 2021, 07:49:25 am
content: This is a common chinese B704 sealant. You can just tear it off gently with tweezers.And it is enough to heat the epoxy resin with a heat gun to a temperature of 90-120 degrees Celsius and it will crumble like clay.

author: perieanuo
author_rank: Frequent Contributor
timestamp: February 11, 2021, 08:09:07 am
content: hi,viewing the price for epoxi, you can just cut the wires 2cm next to pcb and solder the new cable, put shrink tubes instead. you have all the space in the world to do itregards, pierre

author: jpanhalt
author_rank: Super Contributor
timestamp: February 11, 2021, 11:08:15 am
content: Quote from: ledshok on February 09, 2021, 07:48:58 amIf you are talking about isopropyl alcohol (IPA), yes, 100% is better. Some people have problems getting 98% or more IPA. It seems to have just the right polarity (hydrophobic) and viscosity to seep between the hotmelt and whatever the hot melt is on. 91% is the lowest concentration I tested.
black line on tv plasma - Page 1
Forum section: electronics / repair

author: tornedoar
author_rank: Newbie
timestamp: August 18, 2019, 07:54:29 pm
content: i found 3 transistors in X-main board has short circuit so i changed them and now my samsung plasma tv work but has black line on screen and that line not moving at all it is just stay on same place and when the tv off i cant see any lines, so could anyone help me to do and if that because panel or some board or ics?after i finish i will share my experincess with you or as video on youtube.

author: tornedoar
author_rank: Newbie
timestamp: August 18, 2019, 07:56:24 pm
content: this the screen

author: tornedoar
author_rank: Newbie
timestamp: August 25, 2019, 02:24:45 pm
content: mm none can help?

author: shakalnokturn
author_rank: Super Contributor
timestamp: August 27, 2019, 10:35:37 pm
content: I've had a similar case before, single black line, without the multiple thin ones you have.In my case it was one of the line drivers gone defective (usually spread out over 2 PCB's on one side of the TV) sometimes they will burn a small hole in the top of the TQFP package, sometimes the PCB will fuse a power supply track leading to the defective driver IC, otherwise you'll just have to deduce which one is the culprit from the number of drivers and the position of your blank line.In my repair notes I found that I had replaced a defective AN16021AA by a SN755866, a couple of years later the same TV came back with another dead AN16021AA.Some PCB preheat is useful when replacing these IC's the PCB's usually have large ground planes to dissipate heat.

author: tornedoar
author_rank: Newbie
timestamp: August 30, 2019, 11:53:53 am
content: Quote from: shakalnokturn on August 27, 2019, 10:35:37 pmthanks bro you are right, I just check some lines and i fixed it and now the tv work well without high temperature, it is high but it is normal.but I just saw that black line turn to red lines when tv working you will not notice that, but if you focus well on it you can see it, so what the problem do you think? I am thinking seriously about buying new y-buffer, is it could work?
Black screen lg 4k tv - Page 1
Forum section: electronics / repair

author: Fuzz
author_rank: Newbie
timestamp: September 09, 2022, 02:29:45 am
content: HiI have a curious intermittent problem with an lg led TV.Turns on work fine then randomly goes blank. Only remote works no display. Tried a flashlight to check if it's a backlight issue. Could not see any image. Switch off and back on works again for sometime.It's not a timer issue.The tv is 6 years oldAny guess what could be failing?Thanks
Black smoke but cant find damage? - Page 1
Forum section: electronics / repair

author: HobGoblyn
author_rank: Unknown
timestamp: August 09, 2021, 01:55:30 pm
content: Hi all, I did a stupid thing, plugged in a cable into the wrong place while my printer was on (plugging in single pin and got the wrong one)Smoke started to come out and I immediately pulled the cable out (literally started to put it in, saw smoke and pulled it straight out).Board happily remained on but I turned it straight off , removed board and placed under the microscope.In the first pic, the yellow circle is where smoke damage was on the board before I cleaned it, and the red arrow is where I saw the smoke appear.The F3 fuse hasn't blown, the smoke wasn't near R41 etc (but checked them anyway and they're OK)Second pic shows a more zoomed out pic of the board, and RP1 seems to test similar to RP2, RP3 and RP4.Common sense tells me if I saw and smelt smoke and had to clean it up, something must have gone, but I can't find it?Any suggestions?Thanks

author: Manul
author_rank: Super Contributor
timestamp: August 09, 2021, 03:26:51 pm
content: It could be capacitor C3 or something under the heat sink. We dont know what exactly was wrongly connected, description is lacking details.

author: HobGoblyn
author_rank: Unknown
timestamp: August 09, 2021, 04:09:02 pm
content: The touch screen cable has a single pin for +5v, I plugged this into ground. It's a serial cableThinking about it, I probably had the rest of the cable in wrong too.Underneath the heat sink is a TMC2208 stepper driverDon't worry, I'll use it as an excuse to upgrade to a better main board.

author: fzabkar
author_rank: Super Contributor
timestamp: August 09, 2021, 04:58:54 pm
content: Fuse F3 is resettable (polyswitch or polyfuse).Part number = nanoSMDC110Fhttps://www.littelfuse.com/~/media/electronics/datasheets/resettable_ptcs/littelfuse_ptc_nanosmdc_datasheet.pdf.pdf

author: TheMG
author_rank: Frequent Contributor
timestamp: August 09, 2021, 06:10:55 pm
content: I've seen resettable (polyfuse) fuses emit a bit of smoke when subjected to a short circuit or large overload, then with the short removed, the fuse reset and worked fine.They are essentially a special type of PTC thermistor, so they do get quite hot once they trip, sometimes hot enough to burn off any flux or other residue that might be on or under the part.If the board is working fine I would just use it and not worry about it too much.
Blaupunkt BS723 bluetooth speaker - Page 1
Forum section: electronics / repair

author: tjfs
author_rank: Newbie
timestamp: December 24, 2024, 03:34:23 pm
content: I am trying to fix this item, it works except I can't get it to pair. Searching online hasn't found a manual for it. I am wondering if the Bluetooth module is faulty as it works in analogue audio mode.The module has two rows of castellated pins for a total of 24. It uses the CSR 57F68 chip together with a flash chip for storage. The main board has an amplifier chip, stereo mixer, power supplies and a microcontroller which seems to have no markings. I think the microcontroller is working correctly and sends commands to the Bluetooth module via SPI although I don't know the protocol used.It's also possible that it's working correctly but I just don't know how to put it into pairing mode. The usual hold the button methods don't seem to work. I've checked the power rails and they look good.Any help gratefully appreciated.Tim

author: u666sa
author_rank: Frequent Contributor
timestamp: December 24, 2024, 04:56:25 pm
content: It's super hard with the picture you provided. But the chip does not look aligned, at least from your picture and to me personally.
Blaupunkt CR-4096 motor cross reference - Page 1
Forum section: electronics / repair

author: jcoda95
author_rank: Contributor
timestamp: May 10, 2024, 11:09:05 pm
content: I’m looking for a blaupunkt motor part #EMD-58 in an am/fm/cassette unit.Anybody know if there is a cross ref chart for alt motors?It looks like Sankyo was a big source at one time.Thanks,Jeff

author: David_AVD
author_rank: Super Contributor
timestamp: May 11, 2024, 02:36:12 am
content: Is it faulty? If so, in what way?

author: wasedadoc
author_rank: Super Contributor
timestamp: May 11, 2024, 09:17:30 am
content: Quote from: David_AVD on May 11, 2024, 02:36:12 amContinuation ofhttps://www.eevblog.com/forum/repair/blaupunkt-cr-4096-amfmcassette-playing-speed-too-fast/msg5485756/#msg5485756

author: David_AVD
author_rank: Super Contributor
timestamp: May 11, 2024, 12:03:13 pm
content: Oh, so one thread abandoned and another started. Sigh...

author: jcoda95
author_rank: Contributor
timestamp: May 12, 2024, 03:16:23 am
content: Appreciate the response.The motor is playing back at a faster speed.I tweaked the pot to slow I down by ear and then noticed a bit of wow and flutter.Just located a new belt to see if that resolved things a bit. Waiting on delivery.My concern is the speed adjustment is close to the max, so wanted to lTry to find a compatible motor.Thanks,Jeff

author: wasedadoc
author_rank: Super Contributor
timestamp: May 12, 2024, 05:45:50 am
content: Running fast is not a failure mode or aging consequence of dumb motors (those with no integral speed control). If the only provided speed control is the voltage, the fault is with that.
Blaupunkt Frankfurt TR US car radio amp ID - Page 1
Forum section: electronics / repair

author: Jeff eelcr
author_rank: Frequent Contributor
timestamp: July 30, 2022, 12:50:07 pm
content: This antique car radio and seperate amplifier is of coarse 6V not 12V (not + ground at least).The radio part is similar to Sams Photofact 393-7 (tube unit) the amp part is transistor.It is not listed in any Frankfurt models service manuals but I bet it is in some other models.Its visiable features are 3 transistors mounted to the heatsink (rear) and the 4 holes for 2speaker plugs on the side.This was proably built around 1960 it is not switch selectable for power and ground butis selectable by rewiring at least for voltage.JeffUnless someone has a manual for the TR US version.

author: Roehrenonkel
author_rank: Frequent Contributor
timestamp: July 31, 2022, 11:08:27 am
content: Hi Jeff,have a look here:https://www.radiomuseum.org/r/blaupunkt_frankfurt_tr_us_30471_ser.htmlhttps://www.radiomuseum.org/r/blaupunkt_frankfurt_us_ab_q_890001.html.....maybe you have to click on "Schaltpläne".

author: Jeff eelcr
author_rank: Frequent Contributor
timestamp: July 31, 2022, 01:08:18 pm
content: Roehrenonkel, Thank you, that should work perfectly.Nice to know some of the old information is still around.Jeff
blewup my old psu - Page 1
Forum section: electronics / repair

author: ME
author_rank: Frequent Contributor
timestamp: June 01, 2025, 03:32:32 pm
content: I have this old bench psu, it originaly used all transistors from the 60's era ,I am looking to build a lm723 based guts for its case, I want to etch a pc, has anyone a link to a lm723 pcb artwork so i can make new guts for it using the original pass elements etc ? .Thanks.

author: ME
author_rank: Frequent Contributor
timestamp: June 04, 2025, 09:20:09 am
content: anyone?.

author: Kean
author_rank: Unknown
timestamp: June 04, 2025, 11:06:28 am
content: Not surprising you didn't get a lot of replies - you provided very little detail.You say you want to reuse the original pass elements, but also the title states you blew up the PSU. Typically it is the pass elements that are first to go, but if not and you want to reuse them you might need a specific schematic to suit those parts.In any case, a quick Google search for the terms "lm723 pcb artwork" brings up a bunch of designs and articles. Maybe select something and ask questions if you need help in customising it to suit your application. I might not be able to help, as it has been far too long since I last considered using an LM723.

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: June 04, 2025, 12:42:23 pm
content: Yes, more detail. Kean is correct, usually the pass transistors are the first thing to go on PS.What sort of transformer does it use, how many windings? What voltage is required? How many pass transistors and how many amps? Perhaps just a picture and hopefully the schematic of the unit.

author: MathWizard
author_rank: Super Contributor
timestamp: June 05, 2025, 01:11:59 am
content: How many channels does the PSU have ? I just got an old 3-CH supply, maybe from the late 90's, it only used 3 op-amps per main channels, and a uA723 for the 5V CH.I'm figuring out some stuff about how it works, I should put it back together and try it out, but I wanted to check some caps, and made a schematic since I couldn't find 1.I have a couple of ideas to upgrade it a bit, but I don't really know any good linear PSU design's yet, I'm just getting used to the basic's of them.But I already have some new uA723, I'm have to start researching the best design's.

author: ME
author_rank: Frequent Contributor
timestamp: June 05, 2025, 05:33:43 pm
content: The 2 TO3 pass transistors have no markings due to rust,it is 0-50 volt 0-1amp supply,was left charging a battery at 18v 1a overnight and had no output and no drive to the pass transistor bases so i want to make my own innards with what i have some L146 regulators to use so need a pcb same as 723 layout,i need shematic+artwork.

author: coromonadalix
author_rank: Super Contributor
timestamp: June 06, 2025, 10:23:53 am
content: as written you have plenty of schematics floating on the web, 723 designs are well known ... L146 etc ...and once again you provide little ... you have to do your home work at some point ...
Blotchy LCD on my E1 receiver - Page 1
Forum section: electronics / repair

author: najrao
author_rank: Regular Contributor
timestamp: September 29, 2019, 11:54:58 am
content: Eleven years old, and works wonderfully well. Prized possession.The dot matrix display has developed whitish blotches which seem to grow further over the months and years. I have checked that they are under one or other layer of polarizer(?), and not the outer plastic protector. When lighted up by the backlight, the blotches are less obvious.Would there be any way I can clear them up?Group yahoo offered no response.Thank you for any suggestions.

author: najrao
author_rank: Regular Contributor
timestamp: October 12, 2019, 09:07:13 am
content: There was no response, but I showanotherE1MX which has developed comparable display blemish. This time it seems someone used sandpaper to clean it off, but in reality no one could have, it was never taken apart once assembled in the factory. Ignore the crack in the external protective plastic.Thereisa yahoogroups post which suggests peeling off thethreelayers of polarizer, conductive film and another which they put on originally. Apart from defeating the RF screening needed, such surgery is difficult and pretty drastic. Still, if inevitable, ---.Do help me, please, if you know better.

author: najrao
author_rank: Regular Contributor
timestamp: November 21, 2019, 10:13:44 am
content: Well, I did peel off thethreevery thicklayers of plastic film, on both receivers. Took a lot of dismantling, and careful wielding of a new sharp knife.The result isfantastic!Thereissome rf interference from the display, feeding back to the internal telescopic antenna, but this existed even before. Nothing you can't cure by adding a wire antenna to push the signal up to above S5 or so.I write this only to provide a closure to the topic.
Blowing fuses - Page 1
Forum section: electronics / repair

author: tmuropa
author_rank: Newbie
timestamp: May 22, 2019, 09:32:50 pm
content: My Telefunken TV keeps on blowing fused.How do I rectify the problem.

author: Kwakerman
author_rank: Regular Contributor
timestamp: May 22, 2019, 09:38:05 pm
content: Replace the broken bits! Seriously I think you need to give a bit more detail before you will get any worthwhile answers

author: DaJMasta
author_rank: Super Contributor
timestamp: May 23, 2019, 02:04:22 am
content: Something in it is drawing too much current. Look for hot spots, burned marks, charred components, etc., and that's your starting point. Just replacing the fuses won't fix it and could, with time, do more damage.

author: Simon
author_rank: Unknown
timestamp: May 23, 2019, 06:43:33 am
content: Please don't double post, it is very annoying for everyone. If this is a modern TV you have slim chances of repairing it.
Blown 5v Rail - Page 1
Forum section: electronics / repair

author: ajp8868
author_rank: Regular Contributor
timestamp: October 02, 2025, 07:56:18 am
content: Hi All,I've been trying to find an issue with a moving head light fixture, as the pan motor was jittery when moving slow. To do this I was probing around with a scope and DMM to check voltages and PWM on the board.While I was doing this, I accidentally shorted the 28v to the 5v rail when I probed a voltage regulator and slipped 🤦🏻‍♂️After this, almost all chips on the 5v rail (including the stm32 controller), heat up very quickly with voltage applied (current limiting PSU)I've removed the voltage regs and some nearby electrolytic caps, but the measure ohms to gnd are around 8.8.How likely is it that I've blown every chip on this 5v rail? Or, could it still just be one component that's causing the chips to heat?What should I try next?Thanks!

author: ondraN
author_rank: Regular Contributor
timestamp: October 02, 2025, 11:45:07 am
content: The MCU is probably defective, since the inscriptions on it are already dark in the middle (due to severe overheating of the chip inside). If you don't have FW for the new MCU, there's no point in dealing with it further.

author: ajp8868
author_rank: Regular Contributor
timestamp: October 02, 2025, 11:56:06 am
content: Sorry, I should have said this photo was before there were any problems, just for reference. I think that's a shadow from the cable above it

author: Ian.M
author_rank: Super Contributor
timestamp: October 02, 2025, 12:05:49 pm
content: Every chip that gets hot on the current limited PSU is probably dead and will need to be removed and checked for low Vcc to Gnd resistance. Additionally other chips connected to them may have damaged inputs or outputs. Its probably BER, but you might get lucky . . . .

author: ajp8868
author_rank: Regular Contributor
timestamp: October 07, 2025, 10:17:52 pm
content: Thankfully, after removing the chip that was getting the hottest (an op-amp) everything came back to life. Very lucky this time!Thanks for your replies

author: digsys
author_rank: Unknown
timestamp: October 08, 2025, 12:00:12 am
content: Had similar incidents over many years - In MOST cases, the most "vulnerable" semi went first, saving all the others. IF the protection system? kicked in, all else saved. Else, if the shorted component could withstand the heat, also ok. Natural selection :-)
Blown Agilent 11667A 18 GHz power splitter photos - Page 1
Forum section: electronics / repair

author: RAQU_PL
author_rank: Contributor
timestamp: August 22, 2025, 04:25:45 pm
content: I' recently purchased Agilent 11667, 18 GHz power splitter as propably not working. Indeed it is blown.I was wondering if soldering ultra small 50 Ghz resistors on top can result in semi decent frequency response.I do know it won't be full 18 GHz, parasitics compensations etc. but who knows.Any advise will be appreciated.

author: Swake
author_rank: Frequent Contributor
timestamp: August 23, 2025, 08:52:42 pm
content: Quote from: RAQU_PL on August 22, 2025, 04:25:45 pmI believe you meant Ohms. I'm not an RF guy, actually at these frequencies it is somewhat voodoo science for me. However I don't think soldering anything on there is going to make that thing work again at or near those GHz frequencies.

author: EggertEnjoyer123
author_rank: Frequent Contributor
timestamp: August 24, 2025, 07:00:29 am
content: You can try your luck with 01005 resistors but it will probably be way out of spec.

author: ftg
author_rank: Frequent Contributor
timestamp: August 25, 2025, 03:14:41 pm
content: Quote from: EggertEnjoyer123 on August 24, 2025, 07:00:29 amIMO worth a try with some nice RF resistors from AVX (like UBR series) or Vishay. As it's broken and useless as is.Another potential option, if it fits would be ready made resistive power splitter chips.For example Knowles Dielectric Labs PDR06380, which might not be solderable to that spot.But their PDR06390 might.Susumu PS1608GT2-R50-T1 also has a chance of fiting.DigiKey carries both.
Blown cap value - Page 1
Forum section: electronics / repair

author: R-1125F
author_rank: Regular Contributor
timestamp: June 26, 2025, 08:29:04 pm
content: I need to replace a capacitor like the one in the photo. I don't know how to read the code on it. It is a 3528 size tantalum capacitor marked with a capital E and another character that I don’t recognize. I am guessing that it is a 15 micro Farad 25V. Could someone tell me the value of this cap and how to read the code in case I run into another one?

author: indeterminate
author_rank: Regular Contributor
timestamp: June 27, 2025, 08:49:21 am
content: Without knowing the manufacturer it could mean anything.even knowing who made it it could just be a batch number.Find another of the same component on the board and remove / measure it is the only way.chances are that its just a filter cap on a power rail so as long as the voltage rating is high enough for the rail then sumthing around the same size should be fine.

author: coromonadalix
author_rank: Super Contributor
timestamp: June 27, 2025, 11:20:51 am
content: mmm the pc17 marking does not generally fit a capacitor placement ?

author: wraper
author_rank: Unknown
timestamp: June 27, 2025, 11:31:19 am
content: What kind of device is it, on what power rail it sits?

author: R-1125F
author_rank: Regular Contributor
timestamp: June 27, 2025, 01:21:21 pm
content: This in an MSI laptop. I think the "P" designates that the cap is on a power rail. I beleive this is on the 20V power circuit in the GPU area. There is no schematic available for this model, but I compared it to another similar model and it uses 15 microfarad at 25V. I resisted pulling a good one out, but I may have to do that to be sure.

author: wraper
author_rank: Unknown
timestamp: June 27, 2025, 01:47:13 pm
content: Very unlikely that it's a regular tantalum capacitor. Most likely it's either LOW ESR polymer tantalum or polymer aluminum. Anyway, putting 25V regular tantalum capacitor on a 20V rail is a no go. They need at least 30% voltage derating and 60% for actually good reliability. On other hand polymer tantalum and polymer aluminum do not require huge derating.

author: R-1125F
author_rank: Regular Contributor
timestamp: June 28, 2025, 02:35:54 am
content: I think I figured out what it is. It was made by KYOCERA AVX, part number TCOB1E156M8R. According to the datasheet, the code for a 25V 15 microfarad conductive polymer tantalum cap is Ee. The datasheet did not make this easy to find.
Blown Capacitor in Afterglow PL-3702 Xbox 360 Controller - Page 1
Forum section: electronics / repair

author: BrokenXboxController
author_rank: Newbie
timestamp: July 06, 2021, 05:15:47 pm
content: A little silver component on the PCB of this controller seems to have self-destructed and oozed schmoo all over the place. After a bit of googling around, I can't seem to find any spec sheet or circuit diagram for this controller that names this part. I just want to know what it's called so I can buy a suitable replacement. A picture of said component is included in this post. Thanks for your time!

author: flolic
author_rank: Frequent Contributor
timestamp: July 06, 2021, 05:37:47 pm
content: That's quartz crystal glued to the chip. Most likely nothing wrong with that component.

author: BrokenXboxController
author_rank: Newbie
timestamp: July 06, 2021, 05:47:31 pm
content: Oh wow, you're totally right. Guess I'll try and see if the cable is the problem. Thanks!

author: Manul
author_rank: Super Contributor
timestamp: July 06, 2021, 09:33:19 pm
content: Crystal will be fine, but the glue is suspicious. From appearance it reminds me the infamous degrading glue, which degrades with time and starts to get corrosive and electrically conductive. Such glue caused quite a lot if trouble in some consumer products. My friend once gave me a failed subwoofer to fix. It was that glue shorting pins and making the preamp go crazy. Can't tell from picture, but if it is somewhat soft and realeases a liquid when pushed, clean that stuff.

author: MathWizard
author_rank: Super Contributor
timestamp: July 07, 2021, 02:46:15 am
content: OP if you have the a computer/internet and the the controller has USB, you can go to a website that shows all the raw data from your controllerhttps://gamepad-tester.com/or in windows10 just type and run "joy.cpl", thats the little joystick/controller windows, you click properties and then can see what does what and if u can calibrate it.I have 2 broken controllers, 1 has mechanical wear and maybe a worn out poteniometer, and the other seems to have an ADC, or processor, or driver problem, if only I could hack inside it's MCU

author: BrokenXboxController
author_rank: Newbie
timestamp: July 07, 2021, 08:28:41 pm
content: The website shows no response, but that doesn't surprise me. I lopped off the cable and soldered it back together, because the wire was extremely frayed around its connection to the controller. Before I did that no lights would turn on when I plugged it in. After I did that, no lights would turn on when I plugged it in. I'm fairly certain all the four wires are making good contact now, so I'm starting to thing something else is the problem. Maybe the xbox-usb conversion cable thingamajig I'm using, or maybe another component on the PCB. Kind of out of ideas for troubleshooting.
Blown component  - Page 1
Forum section: electronics / repair

author: abdolah
author_rank: Regular Contributor
timestamp: July 31, 2023, 12:05:29 am
content: guys what is this component . and what can I replace it with?! . and is Thier an AC version or DC ?!Component name is TVR . Component on board symbol Z

author: abdolah
author_rank: Regular Contributor
timestamp: July 31, 2023, 12:07:47 am
content: https://drive.google.com/file/d/1hh-5FBtNjLxp0nAT7OR_A0MTu5IXwa8g/view?usp=drivesdkComponent image

author: Vovk_Z
author_rank: Super Contributor
timestamp: July 31, 2023, 12:24:48 am
content: You didn't give access to your file.I can guess 'TVS Z' is possibly a varistor.

author: abdolah
author_rank: Regular Contributor
timestamp: July 31, 2023, 12:26:18 am
content: Try again. I fixed it

author: fzabkar
author_rank: Super Contributor
timestamp: July 31, 2023, 01:02:32 am
content: Many choices ...https://www.google.com/search?q=filetype%3Apdf+tvr0724107 = 7mm diamater241 = 24 x 10^1 = 240V

author: abdolah
author_rank: Regular Contributor
timestamp: July 31, 2023, 01:15:59 am
content: Can I replace it with ZNR . Or VDRAnd what is the difference. BTW thanks for the datasheet 😊

author: fzabkar
author_rank: Super Contributor
timestamp: July 31, 2023, 01:22:46 am
content: Quote from: abdolah on July 31, 2023, 01:15:59 amTo me, they're all the same.https://en.wikipedia.org/wiki/VaristorVaristor = voltage-dependent resistor (VDR)https://industrial.panasonic.com/ww/products/pt/surge-componentsQuote

author: Vovk_Z
author_rank: Super Contributor
timestamp: July 31, 2023, 09:51:06 am
content: Yes, that's 7 mm 240 V rated varistor (150 VRMS). Any 7mm 240 VDC rated varistor should do it (marked as '241').

author: abdolah
author_rank: Regular Contributor
timestamp: August 04, 2023, 01:32:58 am
content: Thanks so much for your helpHow can I know the rated voltage for it . Datasheet?!

author: abdolah
author_rank: Regular Contributor
timestamp: August 04, 2023, 01:35:53 am
content: Thanks 🙏👍
Blown fuse on LK-OP2060-003 rev: 1.2 power board - Page 1
Forum section: electronics / repair

author: Bumblebee001
author_rank: Newbie
timestamp: July 03, 2019, 11:42:35 am
content: Hi guys,I have a 22" TV widescreen by DGM. Model: LTV-2261WCR - PB10PT4. It just keeps blowing one fuse after another meaning there are other components that are bad and need replacing or perhaps - better still - a change of the whole power board.The power board carries these details: LK-OP2060-003 rev: 1.2. I saw one for sale at ShopJimmy but it is Rev 1.1.I am no electronic genius and need guidance on how best to get this TV working again. It has been repaired twice by a local technician and the result is always a few months of use then - pop - the fuse blows again. The guy may have been economical with the repairs yet charges an arm and a leg.I would appreciate some help from this forum.

author: shakalnokturn
author_rank: Super Contributor
timestamp: July 04, 2019, 11:21:11 pm
content: If it is "only" blowing it's own power supply fuse and supposedly the TV repair place are doing their job (not just replacing the fuse), there are a few points you may want to check to start with.Is your mains supply suitable? Bad contacts in plugs, switches, leads? Usually listening closely will give you a clue.Is mains voltage much too low or too high? Running on a generator?

author: Bumblebee001
author_rank: Newbie
timestamp: July 06, 2019, 11:39:31 am
content: There should be no issues with mains supply. Plug checked. I tested TV after replacement of fuse in another house and using another cable. Fuse blown again. It must be the board components.

author: tunk
author_rank: Super Contributor
timestamp: July 07, 2019, 07:12:19 pm
content: I don't know what your problem is, but if you disconnect all output from thepower board and it still blows the fuse, then the power board is the problem.

author: Bumblebee001
author_rank: Newbie
timestamp: November 14, 2022, 11:14:05 pm
content: Any suggestions as to where I could source this power supply?Regards