hybridfree/eevblog-posts huggingface dataset:
Spectra-Physics laser communication problems - Page 1
Forum section: electronics / repair

author: Somethind
author_rank: Newbie
timestamp: July 04, 2025, 07:00:24 pm
content: Hello everyone, I honestly don’t even know where else to turn, so I’m writing here. I have a power supply with a built-in laser from Spectra Physics J20-5540 Rev A. At first, it had a boot error: “Bad relay state.” I managed to fix that, but now I’m facing the question of how to control and turn on this laser. There’s no information about my unit online, and although similar manuals had some information (about communication via Serial-Com), I wasn’t really able to get anything working. I know the device doesn’t require a handshake, and I tried sending commands through HTerm, but got no response. I also tried different baud rates, but that didn’t help either... (all interlocks are enabled and the laser is in standby mode, waiting for a command—what should I do?).Recently, I got lucky and managed to get a remote control head for these lasers (called TREM-Q2), but unfortunately, the cable was cut off and I don’t have the pinout, so I can’t really do anything with it. However, if someone could provide the pinout for it, that would be extremely helpful.So, that’s my situation. I hope someone has advice for my problem.P.S. The serial-to-USB adapter is fully functional and there are no issues with it. What I need is either a list of the correct commands, or maybe I need to send a specific command to let the device know it can communicate via COM.

author: ApertureScience
author_rank: Contributor
timestamp: July 04, 2025, 07:12:58 pm
content: Hi Somethind,You could maybe open up both units and check the internal wiring to the transceiver chip. The datasheet should give you clues as to which is connected where.

author: Somethind
author_rank: Newbie
timestamp: July 04, 2025, 07:18:03 pm
content: Hi, the terminal, well... it goes direct to the motherboard, in the cpu/fpga, it also uses D-Sub 9 connector, so there is not right way to identify, also there is a lot of logic on the motherboard(srr it can not be seen, but the connector for the external terminal is right under text spare

author: ApertureScience
author_rank: Contributor
timestamp: July 04, 2025, 07:25:59 pm
content: Hi, I mean the remote. The pinout can probably be deduced from the internal connections to the IC. From that you can figure out what the loose cables are supposed to be. Do you know the pinout on the laser side?

author: ApertureScience
author_rank: Contributor
timestamp: July 04, 2025, 07:31:31 pm
content: Which connector is it on the board? Next to J9 there are two RS232 chips:Max250,max251

author: Somethind
author_rank: Newbie
timestamp: July 04, 2025, 07:36:23 pm
content: Yes, you saw the isolation rs232 chips, i also cheked them and the voltages across them, they are fine, and therRemote goes in J13 (out of the picture but there is no much to see, the traces are on another side of pcb which go into some logic and then in the cpu, the remote is also does not use rs232
Spectracom 9183 Firmware? - Page 1
Forum section: electronics / repair

author: Whaleback
author_rank: Contributor
timestamp: April 12, 2023, 02:40:17 pm
content: Hi folks,I've just acquired an older Spectracom9183 netclock. It appears to have a very early build of FW/SW.I'm looking for a more recent version of the binary, as mine is running ver 1.20, and the "newest" version this old potato runs is 2.3.1. A lot of features are missing in 1.20.A copy of the binary is stored on the device in the /sys/bin/ folder. The binary can be downloaded from the device via FTP over the serial config port, or via the network interface.I'm hoping for assistance from anyone who owns and operates a 9183, my super long-shot request is for a copy of the 2.3.0 or 2.3.1 bin file.Thanks folks.Patrick

author: Leo Bodnar
author_rank: Frequent Contributor
timestamp: May 04, 2023, 08:59:40 am
content: Code:--------------------------------------------------Spectracom Corp. Model 91XX--------------------------------------------------Application Name: 91XXRevision: 2.3.1Date: 01/05/2006Boot Monitor Rev: 2.3.0--------------------------------------------------PCB Test -> PASSED (PCB rev: 21)PCC test -> PASSED (PCC rev: 3)CSL test -> PASSED (CSL rev: 14)--------------------------------------------------Temp Sensor Test -> PASSEDRTC Test -> PASSEDData Port 1 -> PASSED (rev: 2.03)Data Port 2 -> PASSED (rev: 2.03)Data Port 3 -> PASSED (rev: 2.03)Data Port 4 -> PASSED (rev: 2.03)Data Port 5 -> PASSED (rev: 9.02)Data Port Test -> PASSEDLCD 1 Selftest -> PASSEDLCD 2 Selftest -> PASSED--------------------------------------------------Executable -> 91XX (0x00a5)Product Type -> 9183 (0x0003) EEPROM (0x0003)Product Name -> 9183Options -> (0x18010dfd) EEPROM (0x18010dfd)Executable Test -> Supported Product TypeOptions Test -> VALID--------------------------------------------------Rubidium Selftest -> PASSEDGPS Selftest -> PASSED--------------------------------------------------Code:ftp> ls -al200 PORT command sucessful.150 Opening ASCII mode data connection for '/bin/ls'.dr-xr-xr-- 1 500 500 0 Jan 6 2006 .drwxr-xr-x 1 0 0 0 Jan 1 2000 ..-rwxrwxr-x 1 0 0 40220 Jan 6 2006 ls-r-xr-xr-- 1 500 500 1716220 Jan 6 2006 specapp226 Transfer complete.ftp: 240 bytes received in 0.00Seconds 80.00Kbytes/sec.ftp> get ls200 PORT command sucessful.150 Opening BINARY mode data connection for 'ls' (40220 bytes).226 Transfer complete.ftp: 40220 bytes received in 0.06Seconds 638.41Kbytes/sec.ftp> get specapp200 PORT command sucessful.150 Opening BINARY mode data connection for 'specapp' (1716220 bytes).226 Transfer complete.ftp: 1716220 bytes received in 1.81Seconds 948.71Kbytes/sec.ftp>

author: Whaleback
author_rank: Contributor
timestamp: September 29, 2023, 06:23:09 pm
content: Leo - THANK YOU!I hadn't even checked back on the post, as I hadn't expected to see anyone ever respond.
Spectroline Eprom erasers Models PE-240T and PE-265T missing drawers needed. - Page 1
Forum section: electronics / repair

author: Paceguy
author_rank: Regular Contributor
timestamp: January 04, 2022, 04:06:53 pm
content: Hi, Would anyone happen to have the drawers for Spectroline eprom erasers PE-240T and/or PE-265T's that they can part with. I contacted Spectroline and they want crazy prices plus there is a minimum order clause. Thanks !
Speed control for AC fan - Page 1
Forum section: electronics / repair

author: Bryan
author_rank: Frequent Contributor
timestamp: December 18, 2020, 05:04:01 am
content: All:Does anyone know what type of AC motors these types of fans use. I doubt a light dimmer would work to control the speed and one has to vary the frequency. Motor speed controller etc.

author: amyk
author_rank: Super Contributor
timestamp: December 18, 2020, 08:07:37 am
content: Likely some sort of induction motor - depending on power output, could be shaded pole (lowest power), split-phase, capacitor start, or permanent split capacitor, among others. Without changing the frequency, limited speed control is possible by varying the voltage. Otherwise it is as you say, a VFD will be necessary.

author: Bryan
author_rank: Frequent Contributor
timestamp: December 18, 2020, 05:46:07 pm
content: There is a controller on the line cord but it only varies the fan speed by maybe 10%, I didn't want to crack the case to void the warranty, might do it anyway to see what it is doing, suspect just a pot and a cap.

author: pbarton
author_rank: Frequent Contributor
timestamp: December 18, 2020, 10:15:04 pm
content: Same fan with a speed controller....https://www.amazon.com/VIVOSUN-Inline-Ventilation-Variable-Controller/dp/B01CTM0JF2/ref=sr_1_17?_encoding=UTF8&c=ts&dchild=1&keywords=Household+Ventilation+Fans&qid=1608330416&s=hi&sr=1-17&ts_id=5446824011Depends if the AC motor has one winding (two leads), or two winding's (3 or 4 leads).There are several AC motor speed control circuits if you Google “ceiling fan speed controller”.Strange, the Amazon listing fails to mention that its 110V and 60Hz.

author: Bryan
author_rank: Frequent Contributor
timestamp: December 19, 2020, 09:21:35 am
content: Exact same fan I have. Did a bit of disassembly. Controller uses a Triac (BT138), will try and draw the schematic out from the PCB. I think with different values, potentiometer... maybe one could lower the speed further.

author: Ed.Kloonk
author_rank: Super Contributor
timestamp: December 19, 2020, 11:24:11 am
content: Fine looking soldering job on the black wire there.

author: Bryan
author_rank: Frequent Contributor
timestamp: December 19, 2020, 11:41:57 am
content: Lol, true on that. The one on the output side of the line is worse.

author: NiHaoMike
author_rank: Super Contributor
timestamp: December 19, 2020, 05:38:22 pm
content: At that price, might as well just get a 120mm Delta server fan, print some adapters to mate it to a 6" duct, and build a simple 555 circuit to vary the speed. It would be way more efficient, similar or lower total cost after adding all the parts, and the speed control will actually work over a good range.
SPEEDMASTER Inverter - Speed Motor Problem - Page 1
Forum section: electronics / repair

author: 2X
author_rank: Frequent Contributor
timestamp: December 14, 2023, 08:13:11 pm
content: Hello,I have a SPEEDMASTER Inverter "SM SERIES SUB-MICRO INVERTERS". I put another "Electronic Programming Module (EPM)" from a unit that didn't work to test the EPM module and then my good inverter shown in the display the code "cF". So according to the manual I made a factory reset (Parameter: 48 - RANGE OF ADJUSTMENT: 04). The motor that is connected to the inverter is controlled via a PCB where takes commands from a PC. The problem after the reset is that whatever speed if I select on the program the motor always run with the same exactly speed and the inverter shows always (independently of whatever speed is selected on the PC) 20.0 (I believe this is the output hertz. I changed the “parameter 27” but the same again (my power supply is 230V/50Hz).Do you know what parameter I have to change in order the frequency output of the inverter not to be constantly at 20Hz?

author: 2X
author_rank: Frequent Contributor
timestamp: December 17, 2023, 11:32:01 pm
content: One weird thing. I copy all the settings from an inverter that is in a similar machine and doesn't work again except If I touch the oscilloscope probe on the pins of an optocoupler the motor start works flawlessly in whatever speed I will set for the PC program but if I stop the motor then doesn't start again except If I touch it again with the oscilloscope probe on the pins of the optocoupler.I have the same inverter on another same machine but the password of the invert isn't the factory, so I can't copy the settings. Do you know if I try one by one all the numbers until, I will find the right password the inverter has limit on the tries of wrong password that I can insert and then will lock (like smartphones)?I didn’t read something in his manual (page 41).

author: m k
author_rank: Super Contributor
timestamp: December 18, 2023, 07:29:17 pm
content: Are you sure something else is not controlling that speed, or that you actually changed the speed?Getting an effect with scope probe indicates that touched input is floating.

author: 2X
author_rank: Frequent Contributor
timestamp: December 18, 2023, 07:48:32 pm
content: Quote from: m k on December 18, 2023, 07:29:17 pmHello, I am sure because the other machine is the same and works fine. Do you know something about the password tries?

author: m k
author_rank: Super Contributor
timestamp: December 19, 2023, 05:50:35 pm
content: No.From where you got that wrong password is locking the device?P27 is base frequency, V/Hz ratio.What other settings you have changed from the default?Default speed selection is buttons.How PC is connected to inverter?
Sphero spiderman - Wifi/bluetooth - Page 1
Forum section: electronics / repair

author: Marcel84
author_rank: Newbie
timestamp: July 26, 2021, 09:04:20 pm
content: Hi everyone,I hope someone can help me further with my repair project. Relatively new to it so its a learning curve for me. I'm trying to repair a spiderman bot made by Sphero. If i turn it on, the music plays (so it does something) but it requires wifi/bluetooth to continue and that is where it stops in the app. It gets stuck as in nothing happens and remains trying to find a signal. Hence my guess was a faulty realtek chip (RTL8723CS which are not easy to find) or the antenna. Replacing the antenna did not work unfortunately.Sadly, after replacing the chip with a new one the problem also remained the same and just to be sure with yet another chip still the same problem. So i looks like its not the chip or just very unlucky?What I have noticed and don't understand is the following (see the attachment).At A. The pin at the chip at A (the RFIO) is grounded. I measure continuity between that pin and groundpin. I have checked it for shorts (none) and also measured it using another but same chip that is not mounted on the pcb. Just directly on the chip itself and got the same result. Its shorted on the chip itself (by design since multiple chips indicate the same?) but i don't understand it. Is that normal for a RFIO?At A. Because the pin (chipside) at A is grounded the capacitor is shorted at both sides. Its a 2.2pf capacitor.At B. I think its a kind of coil. Looks like a capacitor but has a bar in it. The datasheet it is mentioned as a coil with value 2n2H. Am I correct to assume that?At C. Shorted because of the pin at A. It should be a 1.8pf capacitor.At D. I dont measure ground at either side. Replaced the capacitor with a known working one. Same result. Its a 22pf capacitor.If i measure continuity from pin A it only goes to D. Not further. If i measure continuity from the antenna it also stops at D. Replacing the capacitor did not had any affect unfortunately.Hence I'm lost. Is it normal that the RFIO is shorted to ground? Has anyone an idea how i can approach this problem further or is it unrepairable?Hope someone can advice me to try something new or share a new thought.Regards,Marcel
Spot welder battery high self discharge - Page 1
Forum section: electronics / repair

author: 7AudioBB
author_rank: Contributor
timestamp: February 08, 2025, 03:02:16 pm
content: I've got a BifRC small spot welder which works great when fully charged but when I store it for a month, it fully discharges (down to around 1V). Is this normal with high C LiPo batteries or is something wrong with the circuit?

author: squadchannel
author_rank: Frequent Contributor
timestamp: February 08, 2025, 03:28:28 pm
content: Is the battery voltage 1V?If that is true, you are over-discharging the battery beyond the 2.5V cutoff voltage and should not charge it.If it goes down to 1V, then it is not equipped with over-discharge protection, etc.Such gadgets should be thrown away as soon as possible. It will burn your house down.

author: 7AudioBB
author_rank: Contributor
timestamp: February 08, 2025, 04:17:07 pm
content: Yes, the battery was at 1.1V when I opened it up and checked. You are right, it's dangerous and I don't trust it. I'm gonna get rid of it.
SPS-9400/MP3090/BK-1692 15V 40A Power Supply Repair - Page 1
Forum section: electronics / repair

author: ZigmundRat
author_rank: Regular Contributor
timestamp: April 04, 2023, 02:59:58 am
content: Having acquired a good BK-1692 supply, I then picked up one that was nonfunctional, figuring I could repair it using the available service manual and schematic, and using the good one as a guide. Unfortunately those docs are for the Ver 1 of the supply and it’s changed a bit since then. If anyone has any newer version schematics they would be appreciated. I asked BK Precision but have no answer yet.Anyway, I was able to effect the repair without much difficulty. It turns out the soft start resistors were both open. These white ceramic resistors can be seen at the upper left side, next to the bridge rectifier (metal square thingy) in the attached photo. They are in parallel in series with the one side of the AC line before going to the rectifier. They get shorted out by the relay just below when it pulls in. I’m trying to get my head around the failure mode here. These are switched out of circuit almost immediately after turn on. So why would they BOTH be open? There’s no sign of heating on them or elsewhere for that matter. Any ideas?Thanks!

author: apefoot
author_rank: Newbie
timestamp: November 08, 2024, 07:38:16 am
content: I have the same BK-1692 variant with the same problem (open soft-start resistors). Was replacing the resistors a permanent solution? Did you ever determine the failure mechanism? Did BK Precision provide a schematic?

author: rfengg
author_rank: Regular Contributor
timestamp: November 08, 2024, 03:03:58 pm
content: Hi there,Try emailing "support@bkprecision.desk-mail.com".......I had contacted them once and they digged out a SM for a power supply that was discontinued since 1992.Pretty helpful folks imo.

author: apefoot
author_rank: Newbie
timestamp: November 23, 2024, 05:47:34 am
content: I replaced the resistors, turned the unit on, and got fireworks in the high-voltage section. Off to Silicon Heaven for that one!

author: aeg
author_rank: Regular Contributor
timestamp: November 25, 2024, 12:57:05 am
content: Maybe it's a shorted switching transistor? It could still be possible to repair.

author: apefoot
author_rank: Newbie
timestamp: December 04, 2024, 05:19:32 am
content: Too many blackened parts for my skill level!

author: Harry_22
author_rank: Frequent Contributor
timestamp: December 04, 2024, 07:07:51 am
content: Hi!Make a photo of fire area from top and bottom.
SRQ annunication on LCD display HP3457a - Page 1
Forum section: electronics / repair

author: pe2ben
author_rank: Contributor
timestamp: May 14, 2023, 06:33:03 am
content: Hello,After power on the SRQ annunciation on the LCD is marked.Also a a double beep sounds. After a while even 3 times this double beep.There is also a ERR annunciation but that is caused by empty battery (already replaced).I have to send out for calibration but first i will try to solve the SRQ annunciation otherwise i could be the case that these calibration is useless.Regarding the SRQ annunciation:The STB? command (reading the status register) turns with 104 (weight i think) but in the manuals i can not find clear explanation.The operational manual (V3) should clarify these but at that way i can't find a reasonable indication.It is a little bit confusing.Also the other manuals leads not to a solution.Maybe someone can clarify things regarding this to me?Thanks Ben
ST W80NE06-10 replacement for RC charger - Page 1
Forum section: electronics / repair

author: Northy
author_rank: Regular Contributor
timestamp: April 04, 2021, 09:34:47 am
content: Hi,I'm trying to fix an RC charger which was pretty cutting edge 20 years ago! I think the main FET is blown, but I can't find any info on it:ST W80NE06-10Does anyone recognise the part number and have any information on it so I can choose a suitable replacement?Thanks,G

author: ogden
author_rank: Super Contributor
timestamp: April 04, 2021, 09:58:32 am
content: Can't find any? Really?https://www.google.com/search?q=W80NE06-10

author: Northy
author_rank: Regular Contributor
timestamp: April 04, 2021, 11:02:49 am
content: I have no idea why my searches earlier found nothing, but I was just about to come here ans say I was having some more success when I saw your reply! Sorry.G

author: ogden
author_rank: Super Contributor
timestamp: April 04, 2021, 01:02:54 pm
content: Do not forget to come back and tell how did repair go.
ST92163 Microcontroller reset stuck on low. - Page 1
Forum section: electronics / repair

author: gkmaia
author_rank: Frequent Contributor
timestamp: August 23, 2019, 07:02:44 am
content: I got a ST microcontroler that is stuck in low.If you look at the attached image pin 36 seems to connect to the base of an NPN transistor and at the same time connects to ground.Pin 35 is the reset, seems to connect to the emitter.The NPN collector if feed from a 5v rail.If I momentarily short the reset pin to the 5v rail then disconnect it the IC boots up.The transistor circuit itself cannot boot the IC but manually I can do it.Anyone out there with some ideas of what could be going wrong here?

author: fzabkar
author_rank: Super Contributor
timestamp: August 23, 2019, 07:26:59 am
content: An NPN transistor in that position makes no sense, but a reset supervisor IC would.

author: gkmaia
author_rank: Frequent Contributor
timestamp: August 23, 2019, 07:30:45 am
content: Quote from: fzabkar on August 23, 2019, 07:26:59 amYes, I agree. Struggling to make sense of that too. I will do some research on a reset IC and see if I can find anything.

author: fzabkar
author_rank: Super Contributor
timestamp: August 23, 2019, 08:09:43 am
content: What are the markings on the "transistor"?There are hundreds of candidates with the correct pinout:http://www.ti.com/lit/ds/symlink/tlv803.pdf

author: gkmaia
author_rank: Frequent Contributor
timestamp: August 23, 2019, 09:19:35 am
content: I researched all over for the marking. Nothing no where.Fzabkar was right. It is a microcontroller reset monitor. TCM809 is probably the right part.The output of my faulty one is not holding the voltage low for the first μsecs.I added a 4.7uf capacitor between the RESET and GND and a 10k resistor between the 5v rail and RESET.Now as the voltage raises slowly the microcontroller detects the raise slope on RESET and the thing booted up just fine.
stabilok 4015  - Page 1
Forum section: electronics / repair

author: ME
author_rank: Frequent Contributor
timestamp: April 30, 2025, 07:13:49 am
content: I brought this,any ideas where i should start?.

author: DeepLink
author_rank: Regular Contributor
timestamp: April 30, 2025, 10:59:19 am
content: First find the service manual for itRead it (just kidding - who reads the manual first anyway)Usually a chapter about trouble shooting / repairCheck power supply, possible in need of a total re-cap

author: Aheld
author_rank: Regular Contributor
timestamp: April 30, 2025, 06:36:25 pm
content: Hi,Recap is necessary. Not only PSU also all ALU Elkos of every modul. I would guess you'll find some of them are wet.Service is relatively easy, because of the modular setup. So, clear statement to buy it.My experiances are based on a complete service of a Stabilock 4032.Service manual with schematics for 4031 and 4032 are available in web for free. 4015 I'm not sure.Br. Axel

author: ME
author_rank: Frequent Contributor
timestamp: May 01, 2025, 01:00:12 am
content: First thing will be look at every cap with uv and look for stains,I am thinking an sm cap pissed itself and munched tracks,its this one.https://www.ebay.co.uk/itm/205440758912

author: Aheld
author_rank: Regular Contributor
timestamp: May 01, 2025, 01:45:10 pm
content: My 4032 had many wet cap's and I would guess that this 4015 is comparable manufacturing date.That was 1 week of recaping and mean while over 7years with no trouble.Br.Axel
Stag Zm3000 Eprom Programmer - Page 1
Forum section: electronics / repair

author: Paceguy
author_rank: Regular Contributor
timestamp: October 31, 2022, 11:16:01 am
content: I have a vintage Stag Zm3000 eprom programmer and I'm looking for a light pen, manuals, and plug-ins for it. YES, I have already been in contact with Matthieu Benoit and given him some photos of mine that are now posted on his site. Please let me know what you have if you have anything related. Thanks in advance!
Start-up Issue of Kenwood/Texio PW18-3AD Power Supply - Page 1
Forum section: electronics / repair

author: heize0
author_rank: Contributor
timestamp: December 07, 2023, 11:42:08 am
content: Has anyone come across the Start-up Issue of Kenwood/Texio PW18-3AD Power Supply?My one was stuck in 'IF- ----' when start-up and had no output.

author: vinovino
author_rank: Contributor
timestamp: December 03, 2024, 07:45:01 am
content: Did you resolve your problem?

author: heize0
author_rank: Contributor
timestamp: December 14, 2024, 05:05:49 am
content: The problem stays unresolved.
Static crackling noise with iDSD Nano DAC - Page 1
Forum section: electronics / repair

author: haizaar
author_rank: Regular Contributor
timestamp: July 24, 2023, 03:07:56 pm
content: G'day forum!I have my good oldiFi iDSD Nanothat I use about once a year nowadays; otherwise it sits plugged into USB ready to go, but switched off.Its battery has been long gone, but otherwise it's been working just fine. Today I switched it on and noticed static, crackly noise. It's very pronounced and, of course, disturbing.I pulled it out of the case. The battery is very "pregnant". I disconnected the batter - didn't help. I powered it from my lab power supply with 4v and indeed it consumes up to 0.2A when playing, but didn't help with the issue either.The board looks clean - no leaks, oxidation, etc.The issue is the same both with RCA and 3.5mm jack (can't test digital output though). Happens the same regardless if I plug the USB into phone or computer.Is there any obvious quick fix to this?Board pictures are attached

author: haizaar
author_rank: Regular Contributor
timestamp: July 27, 2023, 02:45:25 pm
content: After giving DAC an off-grid rest for the night, the problem started to reproduce only when plugged into (any) laptop that is connected to my docking station. After bisecting analysis turned out the source of the issue was my recently installer powerline adapter, which caused this static noise even when there was not RJ-45 cable plugged into it. I.e. somehow that noise it generated on the mains managed to to get through dock power supply -> dock itself -> thunderbolt 4 cable -> laptop motherboard -> my DAC.Go figure....
Static on Pioneer SX780 - Page 1
Forum section: electronics / repair

author: cardoTheCat
author_rank: Newbie
timestamp: January 17, 2021, 06:51:49 pm
content: Well, I don't know exactly how to describe it. It's not the usual "scatchy" pot problem. With the input shorted (I'm using the tape and aux to route the TV through the receiver) it is dead quite. If I plug plug in the TV and mute it, then crank the treble all the way up, on one channel, there is static like between stations static, not hissing. And, as I turn up the volume it get louder and eventually it affects the other channel.I've tried the tape inputs and the aux channel. Somewhat surprising is that the aux channel is affected, it is affect much less. For instance, with the tape input, the static is loud and interfering with the normal audio at 1/4 volume or so. The aux channel is very quiet at 1/4 volume and doesn't degrade until about 1/3 volume.The unit has never been refurbished. I realize that's probably contributing and may be the a good thing to just go ahead and do anyway instead of trying to isolate the exact issue. Cart then horse I suppose.

author: bob91343
author_rank: Super Contributor
timestamp: January 17, 2021, 07:32:10 pm
content: It seems at first thought that the noise is coming from the source, the television receiver. It's gone when you disconnect that.If the noise is generated in the receiver, my first suspect might be those cute 2SC945 transistors, or possibly a bad tiny electrolytic capacitor. Don't 'recap' unless you have a real reason. It's a lot of work and fraught with possibilities of error. At the maximum, replace the power supply filter capacitors but even then I wouldn't unless they show signs of age.
Steinberg CC121 short to ground at USB 5V 5D rail - Page 1
Forum section: electronics / repair

author: tbegal
author_rank: Newbie
timestamp: April 22, 2024, 06:31:16 am
content: Hello my fellow Electronic friends.We have a short to ground on the 5D rail of the PCB. Unit will not start.I have replaced regulator BD6524.Removed C86, it was a little discolored.I have lifted one side of Capacitor C42 and IC13. Components test fine.Short to ground remains.Any ideas anyone? Before I need to remove more components to find the short?Much appreciation in advance.

author: fzabkar
author_rank: Super Contributor
timestamp: April 22, 2024, 06:57:31 pm
content: As much as I hate them, you could use a thermal camera to see what gets hot. Otherwise, use IPA to see which component evaporates it, or a simple touch test may suffice.
Step-down regulator - Page 1
Forum section: electronics / repair

author: ltktomas
author_rank: Contributor
timestamp: June 25, 2021, 09:15:31 am
content: Hi, does anybody know what chip it is? I've tried searching R8110, E6883ERT etc. but without success.I need to lower the current that the IC feeds into those LEDs but without datasheet I'm not able to find out which resistors set the current.

author: Zero999
author_rank: Super Contributor
timestamp: June 25, 2021, 10:10:50 am
content: Quote from: ltktomas on June 25, 2021, 09:15:31 amTry reverse engineering the schematic. Even without the data sheet for the IC, it's normally fairly easy to figure out, which resistor is used for current sensing.

author: bborisov567
author_rank: Regular Contributor
timestamp: June 25, 2021, 11:13:03 am
content: If the leds are wired in series you can just add a resistor to limit the current.

author: voltsandjolts
author_rank: Unknown
timestamp: June 25, 2021, 11:44:38 am
content: R1 and R2 look like they might both be 560 milli-Ohm.Perhaps they are wired in parallel to make a 280 milli-Ohm shunt.In that case, removing either R1 or R2 should half the current.

author: esepecesito
author_rank: Regular Contributor
timestamp: June 25, 2021, 11:56:25 am
content: I've seen same question in reddit. Seems a custom chip. Probably better to reverse engineer the circuit and use an alternative.

author: ErwinsCat
author_rank: Regular Contributor
timestamp: June 25, 2021, 03:46:56 pm
content: my guess is one the resistor near u1, probably r1IIr2

author: ltktomas
author_rank: Contributor
timestamp: June 25, 2021, 04:22:49 pm
content: I tried reverse engineering the schematic and here it is.Rest of the board is a horn circuit.

author: Zero999
author_rank: Super Contributor
timestamp: June 26, 2021, 01:09:38 pm
content: Quote from: ltktomas on June 25, 2021, 04:22:49 pmThere are errors in the schematic, but R1 & R2 are low value resistors and will be used for current sensing. If one of them is removed, it will halve the current.

author: ltktomas
author_rank: Contributor
timestamp: June 27, 2021, 12:05:03 pm
content: Yes, that did the trick.I replaced both resistors for one 0.47R and it's much better. Thanks for help
Steve Ward's DRSSTC Interrupter shuts down when adjusting pulse width - Page 1
Forum section: electronics / repair

author: Verliebt_in_München17
author_rank: Newbie
timestamp: June 08, 2024, 11:27:21 pm
content: Don't know if this is the right place to come to, i suspect it might be about damaged **equipment** but here I amSo early today I've built this DRSSTC Interrupter for my upcoming Tesla coil project and I've ran into a little trouble, the circuit was operating fine the first time I hooked it up, everything was working normally so i hooked up a small 5mm LED with a 330 Ohm resistor to pin 3 of the rightmost 555 timerwhich is the output and is also responsible for adjusting the pulse width with a 5K potentiometer, up until not even 5 mins, mind that the circuit ran for for 5 whole minutes with no problems, the output of the interrupter started spazzing out uncontrollably (which is most likely a curse since that happens with any circuit that i build), i double checked my wiring to no avail, now hooked up the circuit again where everything is working semi-fine again EXCEPT the 555 timer IC which is responsible for controlling the pulse width is somehow not fine, adjusting the pot even a tiny bit causes the interrupter to shut down and seize working and noticably heats up THAT single 555 timer,Any help on clarifying me on how I should troubleshoot this circuit would be gladly appreciated,I will provide my sloppy wiring if anyone specifically wants to see that

author: fzabkar
author_rank: Super Contributor
timestamp: June 09, 2024, 12:18:32 am
content: https://www.diodes.com/assets/Datasheets/NE555_SA555_NA555.pdfPin #7 is connected internally to a "low impedance discharge path". A transistor inside the IC discharges the external capacitor at the end of the cycle. If R4 is at max travel so that pin #7 is directly connected to Vcc, then this transistor will be trying to short the supply rail to ground.IMO there should an additional resistor between pin #7 and the bottom end of R4.
Still issues with my HP 8903a, "mV" range change problem - Page 1
Forum section: electronics / repair

author: Agosto
author_rank: Contributor
timestamp: May 25, 2024, 07:56:00 pm
content: In my previous post ("HP 8903a, "mV" problem" dated May 5) I reported to have found a bad relay K1 on the A2 (Input) board. I replaced that relay (Magnecraft W107 DIP-1) with a Littlefuse HE721A0500. With the original relay, I was able to measure DC voltages down to 0.19V. Below that, I got erratic results.With the new relay in, I can measure DC voltages down to 0.48V, then again below 0.189V down to 0.076V. Between 0.48V and 0.189V the left display turns blank and the right display shows "----". At the same time, I am hearing rhythmic relays clicking, I believe from the A2 board. With the original relay this voltage range was fine but the range below that (0.189V) was bad. So it is reversed.I double checked that the new relay has the same functionality as the original.Following table 3-8 (Page 3-35) of the service manual these voltage thresholds correspond to Special Function codes 1.15, 1.16 and 1.19.Since then, I replaced relays K2 and K3 and confirmed that diodes CR16, 18 and 21 are good. Trigger voltages for K1 and K2 come from U15 Pins 2 and 12. Both outputs shift between H and L about once per second when voltages reach the "critical" ranges (0.189V - 0.48V) causing the rhythmic clicking, I believe.U15 is a 7407. Is it possible that this IC is defect? I was not able to trace back the respective input of 7407 to the latch board (I believe this is where the signal is coming from).Any suggestion where to look as a next step?Many thanks

author: Kim Christensen
author_rank: Super Contributor
timestamp: May 25, 2024, 10:55:23 pm
content: The 7407 is just x6 TTL buffers with open-collector outputs. Should be pretty easy to check that it's operating correctly.The continuous relay clicking sounds like the 8903 is trying to autorange. But because it has a fault, it continues to search without success.

author: Agosto
author_rank: Contributor
timestamp: May 27, 2024, 02:16:53 pm
content: Found the issue: The original relay has an internal connection between pins 2 and 13, the replacement has not. My oversight. Unit works fine now in Autorange mode across all voltage levels.However, I believe I am still not done yet: I started to look at performance criteria and found that "Distortion" at 6V AC is around 0.47% and 0.53% at 0.6V. Spec is <0.01%. Measured with the built-in oscillator. If I use an external signal generator, I get 0.017% resp. 0.05%.I guess I need to look at the oscillator next.
Stinger bug zapper - Page 1
Forum section: electronics / repair

author: dietert1
author_rank: Super Contributor
timestamp: February 28, 2025, 06:27:42 pm
content: Yesterday i successfully fixed a Stinger bug zapper. The UV lamp would no longer light up. I had some difficulties opening the device, but there are 4 philips screws that hold the top cover. One needs a rather long screwdriver to take them out entering from the bottom of the device. I found that diodes D5 and D6, resistors R4 and R6 and the two transistors needed replacement.There is no starter. Heating of the electrodes and ignition of the fluorescent lamp occurs by resonance. Once ignited, current drops and is determined by the inductance of T2 and mains input voltage.Regards, Dieter

author: dietert1
author_rank: Super Contributor
timestamp: October 04, 2025, 09:43:05 pm
content: These days i fixed another similar bug zapper labeled "zfitei" that appears to be a chinese copy. It arrived new without function and had a short in a 1 nF cap that would be C4 in the schematic above. After replacement of that cap it immediately worked.Regards, Dieter

author: BILLPOD
author_rank: Frequent Contributor
timestamp: October 05, 2025, 01:45:35 pm
content: Congratulations Dietert1, A successful diagnosis and consequent repair provide great satisfaction, and sharing that success with others with the same interests is one of the beauties of forums such as this, as most of our daily contacts have little appreciation for the expertiserequired. Thanks for sharing yours.
STM8 blue pill programming not working, GND pin no continuity repair - Page 1
Forum section: electronics / repair

author: dusan
author_rank: Regular Contributor
timestamp: December 05, 2022, 10:30:52 am
content: I just bought another two STM8 blue pill boards from aliexpress from this seller:https://www.aliexpress.com/item/4000044680163.html, both could not be programmed. I found out that the GND pin on the programming header was not connected to ground, probably internal ground did not connect to via or something. Anyway I added small bodge to ground plane and programming now works.

author: radiolistener
author_rank: Super Contributor
timestamp: December 05, 2022, 01:01:19 pm
content: STM32F103C8T6 blue pill has much more resources...

author: ledtester
author_rank: Super Contributor
timestamp: December 05, 2022, 01:42:35 pm
content: You should ask for a refund and write a review detailing your experience.

author: dusan
author_rank: Regular Contributor
timestamp: December 05, 2022, 03:27:14 pm
content: Quote from: radiolistener on December 05, 2022, 01:01:19 pmYes but consumes 30mA and STM8 only consumes 7mA
Stove controls not responsive - Page 1
Forum section: electronics / repair

author: JonHendry
author_rank: Contributor
timestamp: September 06, 2021, 09:47:14 pm
content: Sorry if this is too far afield, topic-wise.My mom’s stove has membrane buttons for setting the oven temp, and the up button has gradually become less and less responsive.Trying to raise the temperature is a matter of searching for the sweet spot, which is often well outside the marked button location. Usually up and to the right.Is there any way to fix this sort of problem, or is it a matter of having to replace the whole appliance?

author: floobydust
author_rank: Super Contributor
timestamp: September 06, 2021, 09:59:54 pm
content: Some appliance manfacturers sell replacement keypads. The membrane keypad can get dirt inside, or just wear out.Need a make and model number to really give advice.
Strange behaviour Schneider SDV434/19 DVD Player - Page 1
Forum section: electronics / repair

author: Ian_99
author_rank: Contributor
timestamp: September 26, 2023, 01:14:33 pm
content: Hi all!I just got my hands on an old, broken, Schneider SDV434/19 DVD Player, and it's gotten me puzzled.When powering it on there's only a lot of noise to be seen on the screen, also no DVD can be read.After a while an image starts to appear... Logically I opened the enclosure and put a soldering iron on the processor's heatsink, to warm it up further.And there was a full colour image on screen now! After removing my soldering iron it started to disappear rather quickly. I can't see anything physically wrong with the CPU...To find out which processor I'm dealing with, I removed the heatsink (which of course was glued on) and it's an MT389DE. I measured 3.3V on it's power input, which is what it should need.Am I missing anything or does this mean the processor is just dead?Here are some pictures:Screen when powered on:Screen after heating up the processor:Internals:Any help is appreciated!!

author: coromonadalix
author_rank: Super Contributor
timestamp: September 26, 2023, 02:06:06 pm
content: could be power supply related issues, noise on the supply lines or bad soldersseeing the main mcu, some residues on it, was there an heatsink on it who fell off ??

author: Ian_99
author_rank: Contributor
timestamp: September 26, 2023, 04:51:32 pm
content: Quote from: coromonadalix on September 26, 2023, 02:06:06 pmI can ask to use someone's lab to test the PSU's quality as I don't own an oscilloscope myself. Using a voltmeter all was looking alright, there's only some loud coil whine when powered off.The residue is from the heatsink I took off myself, I scratched off enough to make the chip text readable. It was some thermal glue, really annoying to remove.
Strange component SMD - Page 1
Forum section: electronics / repair

author: GGMM
author_rank: Frequent Contributor
timestamp: February 05, 2025, 03:58:45 pm
content: hello,On an Agilent video card I have this type of smd component with a strange markingNoted RL1 and other similar ones noted RS1, RS2, R92.The multimeter no continuity so it does not seem to be a self.It doesn’t seem like a resistance, I think.Spécific capacitor?Spécific component Agilent?What is it?your opinion

author: GGMM
author_rank: Frequent Contributor
timestamp: February 05, 2025, 04:25:55 pm
content: I think it's a Transient voltage supressor at 95%if you thing it's other ??cdt

author: benj38
author_rank: Frequent Contributor
timestamp: February 05, 2025, 05:51:52 pm
content: I would expect a TVS to be more beefy. Also, it would most probably have an epoxy-type packaging similar to a diode, and this has more of a look of a passive component.

author: wraper
author_rank: Unknown
timestamp: February 05, 2025, 06:03:30 pm
content: Quote from: benj38 on February 05, 2025, 05:51:52 pmTVS come in different sizes, many are very tiny chip scale (bare silicon die). But IMHO these are either capacitors or varistors.

author: fzabkar
author_rank: Super Contributor
timestamp: February 05, 2025, 06:05:26 pm
content: Is one end grounded?

author: wraper
author_rank: Unknown
timestamp: February 05, 2025, 06:12:24 pm
content: Might be High-Q MLCC, they often have marking. And if they're capacitors, nearly white color indicates stable ceramic, like C0G.

author: GGMM
author_rank: Frequent Contributor
timestamp: February 05, 2025, 06:27:51 pm
content: re,Thank you for your interest in this tough.I confirm, for the components described, one of the legs is to groundThe writing on the smd leaves us thinking.I stick with my idea of a surge protection. I don’t have experience on this type of component, but it is indeed more clear (White) than a standard capacitor. But all is possible for a special capacitor.It’s just curiositycdt

author: benj38
author_rank: Frequent Contributor
timestamp: February 05, 2025, 08:06:13 pm
content: Quote from: wraper on February 05, 2025, 06:12:24 pmIt may also be High-Q RF porcelain capacitors. These are usually white, and often have markings on them (but I have never seen RL1 or RS1 on a capacitor before).

author: benj38
author_rank: Frequent Contributor
timestamp: February 05, 2025, 08:21:28 pm
content: Quote from: GGMM on February 05, 2025, 06:27:51 pmIf you measure one of these with an LCR meter we may get a strong hint.I just measured a few bidirectional TVSs that I have lying around and, unsurprisingly, they all have substantially worse Q (about 5 to 10 times the ESR) than a medium-Q ceramic capacitor of a similar capacitance.
Strange dotted line appears in the middle of laptop lcd screen - Page 1
Forum section: electronics / repair

author: Bram
author_rank: Newbie
timestamp: November 10, 2023, 10:44:21 am
content: Hello community,I have a little issue with the screen of my laptop and hope to get some input from you about the issue.After turning on the laptop (Clevo N970D) a sort of dotted line creeps in in the middle of the screen within a few minutes. It is inconspicuous on white and black backgrounds as the attached image shows and is more prominent with certain colors. Operating system issue is ruled out as the line appears in bios screen too.

author: kripton2035
author_rank: Super Contributor
timestamp: November 10, 2023, 10:45:27 am
content: the lcd display is "dead" and must be changed for this failure to be cured.

author: Bram
author_rank: Newbie
timestamp: November 10, 2023, 10:56:22 am
content: Thank you for the quick input Kripton. For such a thin line I think I'll continue to use the laptop as it is until I get a new one. It's a 4 year old laptop.

author: wraper
author_rank: Unknown
timestamp: November 10, 2023, 10:58:37 am
content: LCD failure. Most likely driver chip bonding issue. You need to replace LCD. Although a crappy fix of placing some piece of foam or something like that to apply pressure on problematic driver chip probably will do the job. But do not expect reliability from that.

author: Bram
author_rank: Newbie
timestamp: November 10, 2023, 06:28:59 pm
content: Thank you very much wraper! I do think also that a simple mechanical fix is possible because the line doesn't appear right away upon turning on but creeps in slowly after a few minutes so there might be some sort of instability at issue here. I have limited knowledge about LCDs but I assume this driver chip is located on the board at the bottom of the LCD screen, correct?

author: wraper
author_rank: Unknown
timestamp: November 10, 2023, 06:59:42 pm
content: Usually there are multiple flex cables along the edge of LCD, each with driver chip bonded on it. Sometimes they can be directly on glass too.

author: Bram
author_rank: Newbie
timestamp: November 10, 2023, 07:19:10 pm
content: Very helpful, thank you! I will proceed with a disassembly and see.

author: Jwillis
author_rank: Super Contributor
timestamp: November 11, 2023, 04:43:12 pm
content: Quote from: Bram on November 10, 2023, 07:19:10 pmBefore you get carried away checking chips. Check the adhesive bonds to the to the LCD. Very common for those flex cables between the control boards and LCD panel to loss adhesion.They can be reattached with a Flex Cable Bonding Manual T Type Solder Tip.

author: Bram
author_rank: Newbie
timestamp: November 12, 2023, 04:27:12 pm
content: Thank you for your precious help Jwillis! I will definitely take a close look at those too.

author: Greybeard
author_rank: Frequent Contributor
timestamp: November 13, 2023, 08:40:59 am
content: What is the rubber thing used for?