hybridfree/eevblog-posts huggingface dataset:
Repair Question about Fuses - Page 1
Forum section: electronics / repair

author: LoveLaika
author_rank: Frequent Contributor
timestamp: June 10, 2020, 03:17:00 pm
content: I'm in the middle of repairing a device, a TSP controller. I'm still kind of running diagnostics on it to make sure that it wasn't anything external, but I wanted to ask a question about fuses and how devices work at different input voltages.This device I'm trying to fix has two input settings: one for 220 V and one for 120 V. The 220 V setting requires the use of 8A fuses while the 120 V setting uses 15A fuses, so depending on the input setting, you have to change out the fuses. If it was set to 220 V while not changing out fuses correctly, so you would be using the 15A fuse, would it still work? The fuses just cut the circuit if the amperage of the fuse goes too high, but it's not a catch-all, right? If it was connected to a power strip (220 V with a 10 A fuse), I would think that the 10 A power strip fuse would break first before the 15A fuse, but is that always the case?

author: themadhippy
author_rank: Super Contributor
timestamp: June 10, 2020, 03:54:14 pm
content: QuoteNo,its possible the 15A fuse could blow before the 10A it all depends on the type of fuse and the fault current.The information on how quickly a fuse blows for a given current can be found on the i/t graph for that type of fuse

author: LoveLaika
author_rank: Frequent Contributor
timestamp: June 10, 2020, 04:00:35 pm
content: Thanks. The manual for the controller states that it uses slow-blow fuses (5x20), while the power strip uses a ceramic fuse. I don't know exactly what the conditions were when the power strip fuse blew. All I was told that the controller was working fine when the strip fuse blew the first time, and when it blew the second time, the power strip only had the controller plugged into it.

author: LoveLaika
author_rank: Frequent Contributor
timestamp: June 10, 2020, 05:25:47 pm
content: Quote from: themadhippy on June 10, 2020, 03:54:14 pmGoing back to the other case, using 220 V with the 15 A fuse meant for 120 V, the controller would still work properly, it's just at a risk of drawing more current than what it safely needs, correct? Assuming that everything is fine with the power strip, under normal conditions, the controller can draw up to 8 amps (else fuse blows), but with an incorrect fuse, it can draw more than 8 amps, which could potentially damage the equipment in the worst case.
Repair Resistor Decade Box - Yokogawa 279301 - Page 1
Forum section: electronics / repair

author: chinhcheng
author_rank: Contributor
timestamp: September 26, 2023, 04:25:03 pm
content: Hello,I just bought a standard resistor box on ebay, Yokogawa 279301 (1mohm resolution)I checked after receiving it, and discovered that the solder connection to the terminal was broken.I want to ask, can I re-solder the weld joint by normal solder?If can not, pls advise me type of solder that is ok in this case?'tks so much.

author: TimFox
author_rank: Super Contributor
timestamp: September 26, 2023, 04:34:58 pm
content: Can you repair that connection by just re-heating the existing solder joint, without adding more solder?

author: SeanB
author_rank: Super Contributor
timestamp: September 26, 2023, 05:44:58 pm
content: Yes just apply a little sticky flux, and melt the solder again, and it will work, unless the terminal itself has cracked. Will not do much change except for possibly 1mR change. If terminal is broken you will need to replace it, easiest to use the ground terminal below, and use it in place of the existing one, as the terminal type is the same, and the broken one will still work as ground, as the insulators stay in position there.
Help Repair Rigol DG1022 - Page 1
Forum section: electronics / repair

author: Giovanni62
author_rank: Contributor
timestamp: April 13, 2021, 05:08:08 pm
content: My Rigol DG1022 function generator, the CH channel stopped working; no output signal. The self-test does not give errors. I noticed that by selecting the CH2 output, when I change the waveform you can hear the relays working, instead when the CH1 output is selected, the relays do not work when I change the waveform type. Any suggestions?
Repair Rohde & Schwarz Test Receiver ESV 342.4020.53 - Page 1
Forum section: electronics / repair

author: Kibabalu
author_rank: Regular Contributor
timestamp: March 06, 2021, 06:28:56 pm
content: Dear collegues,found an old test receiver from Rohde & Schwarz, ESV 342.4020.53, in the store room of our lab. The unit is more than 20 years old, maybe even 30. Last calibration has been 10/99. The person who bought and used it retired approx. 15 years ago. At least this was told to me from the oldest employee of the group that is driving the lab. Back in the time when the unit was bought we used to develop our own measurement systems, including a wireless measurement data transmission system for car testing on test tracks. Today such things are simply covered up by wifi, but in these days you had to develop it by yourself.After towing it to my desk, this guy seems to have more than 20 Kg, I switched it on and nothing happened. I found a melted fuse at the backside and exchanged it, but the new fuse also melted immediately. I opened up the power supply and found a big 10000uF capacitor (see 1st picture) with a shortcut inside (resistance approx. 150mOhm). Most likely dried out? Anyway, I exchanged it with two parallel 4700uF capacitors I found in one of my boxes and that fixed the problem.The unit is now back in life. The last picture shows a test with a 200MHz carrier frequency modulated with a 1kHz signal. The measured signal strength was a little bit smaller, less than 1 dBuV, than the nominal transmitted strength of -6dBm resp. 100.99 dBuV. But I don't know how precise the transmitter really is, I used a tinySA as transmitter for the test, and how big the losses of cable, 50cm of RG142 should be neglectable, and the adapter from N-type / SMA are. For me the unit seems to work fine.The Tek 2465B on top of the ESV shows the demodulated signal delivered by an output port on the backside of the test receiver.
Repair RS SMIQ03B with Error 211 Summing Loop Unlocked - Page 1
Forum section: electronics / repair

author: mcckevin
author_rank: Contributor
timestamp: September 25, 2020, 08:02:49 pm
content: Hi –I recently pulled an R&S SMIQ03B signal generator from my “To Fix” pile. I’ve run into a problem that I could use some advice solving. Some details follow:The internal battery in the front panel control unit had petered out, which caused the loss of the calibration memory. I replaced this battery, then ran the Utilities/Calib/All/Calibrate All calibration routines. These routines returned the following errors:ERROR IQCON no convergence180 Calibration failed; Level presetChecking the logged errors, using the ERROR key on the front panel produces:ERROR -313 Calibration Memory Lost; LVL PRESET – run internal calibration;ERROR -313 Calibration Memory Lost; ALC OFF MODE = TABLE; run LEARN TABLE;ERROR 110 Output unleveled; ALC failureLooking at the signal generator’s output on a spectrum analyzer showed me that the frequencies were accurate but that the output power was about 15 dB too low. Also, the harmonic content of the output was through the roof – the second and third harmonics were only about 10 dB below the fundamental.These data pointed toward V104, the SHF-189 NFET in the IQ-MODULATOR block, as others have had this NFET fail. Probing with a multimeter revealed that the biasing on this transistor was incorrect, compared to the data sheet and to the other FETs in the the RF chain. Replacing the SHF-189 fixed the power output and harmonic distortion problem.But now, I’m stuck. When I look at the signal generator’s output on a spectrum analyzer, the power and harmonic content are reasonable but now the frequency is sometimes not correct. The SMIQ03B occasionally flashes anError 211 Summing Loop Unlockederror that coincides with the incorrect output frequency. I hadn’t seen this error before working on the IQ-MODULATOR board.So, I’m not sure if the 211 Error was masked by the bad SHF-189, or if it’s a new error (something that I caused when replacing the NFET). Or, the problem could be rooted in the ERROR 313 Calibration Memory Lost error caused by the dead battery in the control unit.The table displayed under Utilities/Calibrate/VCO Sum looks reasonable (i.e. close to the one displayed in the user manual).However, the tables under Utilities/Calibrate/Lev Preset (for the IQMOD-CW, IQMOD-VM and IQ-CON) are all filled with +128.0, which seems incorrect to me.So, there is stands. I’d appreciate any help or hints (or even sympathy). Thanks!Kevin
Repair services for a Xilinx ZCU102? - Page 1
Forum section: electronics / repair

author: rmoorepgh
author_rank: Newbie
timestamp: November 20, 2021, 09:46:54 pm
content: Full disclosure, I joined the forum just to ask this question, but do have an interest in circuits, circuit board etc. Here goes:I recently damaged a Xilinx ZCU102 (Zynq Ultrascale+ MPSoC reference board) .. the metal end of a bread-wrapper/twisty tie that was attached to the power cable managed to short out the pins of a surface mount chip (causing it to glow intensely and then die). Lead times and cost to replace the board have gone nuts, so I'd like to get the board repaired. Note to self: never allow metal core twist-ties to be used as cable ties again...Tried Xilinx first, they have no interest in repairing the reference boards they sell and referred me to the CM that makes the board, Whizz Systems (https://whizzsystems.com). Whizz has been completely unresponsive so I'm ready to go looking for a competent 3rd-party shop that could replace the damaged chip(s) and get the board running again.Questions:- is this even possible/practical these days? (One chip is cleared fried, the smoke escaped and I assume this is the one whose pins were shorted. But others might've been damaged as well and I'd have to rely on the shop to determine that)- Are there any reputable/competent repair services that would be capable of getting this board back into working shape?- should we just write this off and try to get a new one?Thanks!Rich

author: BreakingOhmsLaw
author_rank: Frequent Contributor
timestamp: November 20, 2021, 10:52:04 pm
content: QuoteFirst rule of getting support:Call, don't write.I cannot count the number of times where writing a mail to the contact address has gotten me nowhere, and a 5 minute phone call got me what I wanted, plus getting networked with a lot of nice people on top.They have phone numbers on their contact page.

author: rmoorepgh
author_rank: Newbie
timestamp: November 21, 2021, 06:06:15 pm
content: OK, I'll give that a try. In this day and age, some people/businesses barely use a landline phone anymore so it's easy to forget that's an option.

author: james_s
author_rank: Super Contributor
timestamp: November 21, 2021, 06:15:51 pm
content: It would help to know what chip blew up, that could make a big difference on how feasible it is to repair the board and how specialized the service you need is.
Repair shop for Tek DPO4054 scope - Page 1
Forum section: electronics / repair

author: jmelson
author_rank: Super Contributor
timestamp: December 14, 2023, 12:18:42 am
content: Hello,We have a Tek DPO4054 at work that has been a great scope. But, one day, one of the channels showed crazy artifacts, like one bit of the ADC was stuck.Tek wants $4530 flat rate to repair it. Can anybody recommend a shop that can repair these for a better price?I'm taking a wild guess that it could be a bad solder joint on the ADC BGA, but that's just a guess.Thanks,Jon

author: Testtech
author_rank: Regular Contributor
timestamp: December 15, 2023, 12:32:23 am
content: Contact Norway Labs,www.norwaylabs.comThey can fix it.

author: jmelson
author_rank: Super Contributor
timestamp: December 15, 2023, 07:52:40 pm
content: I looked up reviews on Acme Revival - they were 100% terrible! Any unbiased reviews of Norway Labs?Thanks,Jon
Repair Sky-Watcher mini astro tracker. - Page 1
Forum section: electronics / repair

author: dasdboot
author_rank: Newbie
timestamp: January 07, 2023, 09:20:43 am
content: Hello everybody. Thank you for the opportunity to share this with the community. I'm in the process of repairing the PCB inside the Sky-Watcher. So far I identified a blown buck booster dc-dc converter integrated circuit (IC). The IC is responsible for boosting two AA butteries voltage to 3.3v needed by the CPU and the rest of the circuit. Unfortunately from the markings which I managed to recover (6sF and P714) i can't pin it to any manufacturer or the IC identification.I would really appreciate your help. If anyone could recognize the markings or have an idea where to direct my search, i would really appreciate it. Please see the pictures attached.Thank you heaps!

author: dasdboot
author_rank: Newbie
timestamp: January 09, 2023, 12:08:44 am
content: Someone at Electronics.StackExchange suggested the answer. It is Diodes AP6714. Perhaps it might be useful.

author: ingalopez
author_rank: Contributor
timestamp: January 09, 2023, 11:49:33 pm
content: Hi.It may be a last resource, but if the chip cannot be identified, maybe you can bypass the whole converter and "implant" a converter power board, you can find them on line for few$$. If there is enough room.!
Repair Sony PVM-1443MD - Page 1
Forum section: electronics / repair

author: decoder_82
author_rank: Regular Contributor
timestamp: November 06, 2021, 02:28:57 pm
content: Hello,I am trying to repair a PVM-1443MD that when turned on doesn't display the image(but the sounds work ok).What I have checked:- Voltages from the power board are OK- Visual inspection of components on main board, no capacitor that looks bad orburned component- The filaments are glowing when turned on- On the CRT neck board, I have G2 voltage but I get 0 volt for G1.I have two PVMs with exactly the same symptoms, so I guess it is a common failure.Does anyone has some suggestions on where to look at next ?Many thanks!

author: decoder_82
author_rank: Regular Contributor
timestamp: November 07, 2021, 07:06:38 am
content: Update, after reflowing some solder joints, I now get an horizontal blue line on the screen.

author: decoder_82
author_rank: Regular Contributor
timestamp: November 07, 2021, 03:32:40 pm
content: In the end I solved the problem myself. I noticed that IC501 was not getting 12v vvc then further investigation revealed that IC505 in the 12v regulation circuit had bad joints. After reflowing it the issue was solved.
Repair SR620 (schematics wanted) - Page 1
Forum section: electronics / repair

author: Ernesto
author_rank: Newbie
timestamp: October 23, 2022, 01:36:52 pm
content: I have a Stanford research SRS620 Universal Time Interval Counter.Some times during startup I get an "Test Error 17" from the manual I read this is some hardware failure on channel 2.The device also get very warm. Especially the right side front side where the frequency inputs are. Also the right side of the housing where some power transistors (TIP42CQ) are attached to the housing.Unfortunately I can't find any schematics.Can anyone help me? perhaps you have the schematics?

author: BreakingOhmsLaw
author_rank: Frequent Contributor
timestamp: October 23, 2022, 04:08:46 pm
content: Service manual without schematic, but part number for all components:https://www.thinksrs.com/downloads/pdfs/manuals/SR620m.pdf

author: edpalmer42
author_rank: Super Contributor
timestamp: October 23, 2022, 06:41:07 pm
content: Two versions. I don't know which is better.http://www.ko4bb.com/getsimple/index.php?id=download&file=02_GPS_Timing/Stanford_Research_Systems/SRS_SR620_schematics.pdfhttp://www.ko4bb.com/getsimple/index.php?id=download&file=02_GPS_Timing/Stanford_Research_Systems/SR620_Universal_Time_Interval_Counter_Schematics.pdf

author: Ernesto
author_rank: Newbie
timestamp: October 23, 2022, 07:33:46 pm
content: WOW great! Thanks!
repair Tacklife MDC-01 - Page 1
Forum section: electronics / repair

author: RustyShackleford
author_rank: Regular Contributor
timestamp: May 27, 2025, 04:22:27 pm
content: I've got a pair of these cheap bench power supplies, Tacklife MDC-01. One of them has stopped working. Has anyone repaired one of these ?This post does have what appear to be the schematics:https://www.eevblog.com/forum/testgear/cheap-variable-switching-power-supply/msg1240531/#msg1240531

author: Xena E
author_rank: Frequent Contributor
timestamp: May 28, 2025, 09:53:00 am
content: Quote from: RustyShackleford on May 27, 2025, 04:22:27 pm Then it's probably faulty! What haveyoudone so far to trace the fault?One I had dealt with had an O/C input fuse and the bridge rectifier had shorted, no other faults were found.YMMVX

author: RustyShackleford
author_rank: Regular Contributor
timestamp: May 28, 2025, 05:46:04 pm
content: Quote from: Xena E on May 28, 2025, 09:53:00 amJust a hunch, but I think you might be right :-). I've done nothing so far (except buy two more from Amazon which were both DOA, and then buy one that is more expensive and hopefully better from Digikey).QuoteWorth a try - I'll open her up and have a looksee.
repair:  TCA-1MEG and P7260 and P7380  firmware - Page 1
Forum section: electronics / repair

author: charlyd
author_rank: Frequent Contributor
timestamp: January 23, 2022, 04:08:44 pm
content: Hello i want to start a new topic here about repairing a couple of tek probes.i am convinced as we can bundle power here, we can work out lots of failed probes in future and get them to life.and also when you ever have a broken probe you can get info of all kind here. remember it can overcome your probe also !!to start with is firmware content and or test software for one of these Tekconnect probes TCA-1MEG and P7260 and P7380.who can post an earlier made reverse schematics from one of these P7260 or P7380a content export from the 24C16WP from the TCA-1MEG would still be very welcome.refering to some earlier links:https://www.eevblog.com/forum/repair/eeprom-dump-file-from-a-tca-1meg-console-adapter/msg3843410/#msg3843410https://www.eevblog.com/forum/testgear/tektronix-tca-1meg/msg3564832/#msg3564832https://www.eevblog.com/forum/testgear/show-us-your-probes!/msg936191/#msg936191all sort of usable info is welcome: for example are probes like P7260 ( 6Ghz Active Voltage TekConnect Probe) and P7380 ( 8Ghz Z-Active Differential TekConnect Probe) recognised by the a TDS7404 scope or not. Maybe because of limitations of some kind. Perhaps somebody with a working P7380 and/or P7260 is willing to post a screenshot of a test on there TDS7000 series and post the output here?as i wil post a no working TCA-1MEG

author: calibrationfixture
author_rank: Regular Contributor
timestamp: December 17, 2022, 08:57:29 am
content: Hi,The P7380 Series are compatible with the TDS7000B Series. Not all functions are supported. For this you must have a TDS6000(B/C) Instrument.Source: Tektronix Product Catalog 2005 (the last big one?) page 130. I don't know if the P7380 Series are compatible with the TDS7000 Non-B Series. In addition, maybe you must install Tek Connect Adjust Software V1.1 (2002). This supports P7260 Probes.Greetings and succes,Calibrationfixture

author: KrudyZ
author_rank: Frequent Contributor
timestamp: December 17, 2022, 06:26:22 pm
content: The P7380 is compatible with the CSA7404 (non-B) version, which is basically the same as the TDS7404.

author: jensrasmussen.jr@gmail.co
author_rank: Newbie
timestamp: January 26, 2023, 12:12:03 am
content: I use P7260 on my CSA7404 without issues.
Repair Tek 577/177 left/right switch - Page 1
Forum section: electronics / repair

author: PaulAm
author_rank: Frequent Contributor
timestamp: May 18, 2020, 10:15:43 pm
content: If anyone has a 577 you'll know the left/right switch on the 177 text fixture has a tendency to be broken off. The NOS switch is pretty much unobtainable but it is possible to effect a repair.The switch is a Switchcraft 41000 series with 4 sets of contacts. This switch has contacts which are attached with screws onto an actuator body. The details of the body determine if it is an On-Off-On (3 position), On-On (2 position) and locking or non-locking. The one in the 177 is a 3 position locking switch.The correct actuator body can currently be obtained from the Vintage TekMuseum.If you cannot source it from them, you can get a Switchcraft 41312L or 41324L, strip off the contacts and have the correct part.However, the toggle (the part that breaks) is common to the entire 41000 line so you can get the part from ANY 41000 series switch, 2 or 3 position, locking or nonlocking and fix the original actuator. I found one on ebay under "USA made Switchcraft Toggle 1P1T Momentary Tele-Paddle PTT Switch" for under $6 US shipped. The actuator shape is unique to the 41000 line so it's not too hard to identify one once you know what to look for.Use a small pin punch and drive out the pin in the barrel holding the toggle in place. Be careful since there's a spring between the toggle and the rocker in the body. I'd do this to the new part first so you can get an idea of how the switch is put together. I used a filed down finishing nail as a punch.Take the actuator out of the 177 fixture. Remove the looping compensation variable capacitor by unsoldering the rear wire, then removing the knob and nut. You may have to unsolder a couple of the wires on the switch to get it out. Bend it back and unscrew the switch contacts to remove the actuator. Leave the screws in the contacts so none of the spacers fall out. Do not joggle it.Punch out the pin holding the broken toggle. When the pin is almost out you should be able to pull it the rest of the way with pliers (it helps to hold the actuator upright when doing this). Hold the toggle so it doesn't shoot out. Insert the new toggle and spring, put in the pin and tap it home. You want the head of the pin just below the threads so the nut spins down.If you do this carefully you won't disturb any other parts of the actuator mechanism. There are 2 tiny wheels, two tiny axles and a rocker in there that could fall out if you're not careful. If they do fall out, put them back in. They only fit one way.Check the action. It should work like a new switch.Reassemble. Be careful to get the contacts aligned correctly. You want to have the paddle off the switch before trying to get it back in the fixture.I've attached a picture of the repaired actuator with the old broken toggle and spring.Reassembly is left as an exercise for the student
Repair Tektronix 2467B, A5 SMD version board - Page 1
Forum section: electronics / repair

author: lanza2005
author_rank: Contributor
timestamp: December 23, 2021, 10:23:04 am
content: I have a Tektronix 2467B, with problems on the A5 board. As usual. The open capacitors and the liquid, through the plate. After changing them, the TRACE is only visible when I move the INTENSITY knob and then disappears. Can you advise me, where to put my hand? Thank you very much and greetings.

author: lanza2005
author_rank: Contributor
timestamp: December 26, 2021, 02:30:57 pm
content: IMG

author: lanza2005
author_rank: Contributor
timestamp: December 26, 2021, 02:36:51 pm
content: The capacitors are already changed and the tracks checked. Clean the plate with 96º alcohol. Also the capacitors of the power supply. Any advice? Thank you.

author: Joust
author_rank: Contributor
timestamp: February 26, 2022, 02:59:32 am
content: i just got a 2467b as wellIts doing almost the same thing although mine stays on for a few seconds after touching the knob to refresh screen.i haven't opened mine at all yet but was searching for similar problems.dont know if i have SMB board or not yet. hoping not because i have no reader to get sram data out of dallas chip.Can anyone offer advice to Lanza?

author: jxjbsd
author_rank: Regular Contributor
timestamp: February 28, 2022, 03:58:46 am
content: https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/Go to this thread to ask questions.

author: grumpydoc
author_rank: Super Contributor
timestamp: February 28, 2022, 08:20:35 am
content: The grid bias adjustment looks to be off.Any errors on start up? Especially test 04 fails?Your repair seems to be missing some components, notably the potentiometer used to adjust the DAC reference current (and hence output) and an associated resistor R2015When cleaning PCBs I use a 1/2" paintbrush with the bristles trimmed down to about 7/16" (i.e. about 1cm) - something like that would do much less damage to the silkscreen than whatever was used on your PCB.

author: jonpaul
author_rank: Super Contributor
timestamp: February 28, 2022, 11:16:28 am
content: Bonjour, Normally A5 SMD cap leakage (there are may of the caps) damages nearby components and eats internal traces on the PCB. The fluid causes the copper to becone unslderable, give away i a odd smell on heated traces and joints.Suggest a very deep inspection, removal all affected parts. Total clean of board, check trace continuity.If the DAC and REF ckt is not perfect, all sorts of control oddities, as the scope is "fly by wire"See very long threads on this in the old 2465B teardown, also excellent Groups.io TEKSCOPES, and TEKSCOPES2ask there, many ex TEK experts.https://groups.io/g/TekScopes/topicshttps://groups.io/g/TekScopes2/topicsBon Chance,JonPS: A5 had the notorious Dallas 1225 NVRAM with dying /dead Li batter that holds all CAL.
Repair tektronix TDS 220 no screen (white screen) - Page 1
Forum section: electronics / repair

author: afton
author_rank: Newbie
timestamp: April 14, 2024, 01:58:59 pm
content: Regards,Please allow me to ask, I'm having a problem, suddenly my Tektronix TDS220 oscilloscope doesn't produce an image or a white screen, the CFL light is on. I tried checking the PIN 1 voltage (Vo = LCD Contrast adjust voltage) on the LCD connector which is equal to 0 volts, and the PIN2 voltage (Vee = Power supply for LCD (-24V)) is also 0 volts, please give me instructions and guidance on what other steps to take. what should I fix?I really hope to be able to revive the oscilloscope.Thank you for all the instructions and guidance

author: m k
author_rank: Super Contributor
timestamp: April 21, 2024, 02:34:33 pm
content: You should dig up the missing voltage.If no schematics is available you must trace the route back the hard way.

author: rh100605
author_rank: Regular Contributor
timestamp: April 26, 2024, 01:48:31 pm
content: Hi,Did you measure all the power supply voltages at the socket on the main board. The specifications for each pin are in the service manual.If they are not correct then unplug the power connector and measure the outputs of the power supply again.

author: li_gangyi
author_rank: Newbie
timestamp: May 19, 2024, 07:27:11 am
content: I just had something similar happen on my TDS210, Pins 1 & 2 on the display connector measured ~-6V (slowly rises from between -4V to -6V, then drops back to -4V).Disconnecting and measuring the connector on the board results in a stable -24V, so it appeared like there's a short in the display itself. I then took the display module out of the case and measured across the 2 small 25V 3.3uF caps near the flat flex connector and found one with a 160Ohm short.Removed that offending cap and soldered on a 50V 10uF that I had lying around, that solved the short and allowed the scope display to work again post reassembly.Service manual I used is linked below (I did also verify the PSU voltages were fine and I had scope probe compensation output).https://w140.com/tekwiki/images/5/52/071-0492-03.pdf
Repair this part - FB - Page 1
Forum section: electronics / repair

author: almamater
author_rank: Regular Contributor
timestamp: April 09, 2021, 10:11:02 am
content: Hello.Recently my LG Mini Hifi XA14 stopped working, the problem:The +5V input (from Power Supply) had burned! So, i clean everything and put two wires (just for test) and with other power supply (ATX) it worked!So, i check the original power supply, changed one diode and capacitors, and now the voltages are OKAnd i tested all again with the original Power Supply and works!But now i have one doubt, the 2 two components "FB" at the entrance of the + 5V exploded:So I researched and they would be "Ferrite Bead", in the servicemanual(page 38) is the following:what kind of protection can i put there now? What type and value of ferrite can i use? I only have this kind off ferrites here:

author: almamater
author_rank: Regular Contributor
timestamp: April 12, 2021, 10:33:28 pm
content: Can i use two "330uh 400ma" ? It's what i find near me..

author: perieanuo
author_rank: Frequent Contributor
timestamp: April 13, 2021, 08:15:43 am
content: or this:

author: Ian.M
author_rank: Super Contributor
timestamp: April 13, 2021, 09:13:37 am
content: No. You need to find the specs on the ferrite beads and at a minimum troughly match the DC resistance. Is there a BOM in the service manual you can get a full part number from?

author: almamater
author_rank: Regular Contributor
timestamp: April 13, 2021, 09:41:46 am
content: I only can find the service manual (link) but it only have this reference "300RH" on page 38.Its possible remove and check the values from another one?

author: Ian.M
author_rank: Super Contributor
timestamp: April 13, 2021, 09:56:29 am
content: "SECTION 4 ........REPLACEMENT PARTS LIST" is missing from the manual you linked. Try to find an alternative copy that has that section.There's no need to remove any from circuit to measure them, simply unplug PN1/CON9 to isolate one end of them.They've obviously acted as fuses (poor ones as they burnt the board) and it would be desirable to maintain their over-current protection. If you can find some slip-on type ferrite beads as usually used for through-hole applications, you could transplant two of the good '300RH' ferrite beads from 'MGND' pins of the header, and replace them with slip-on ferrite beads on wire links.
Repair: TI 58C - Page 1
Forum section: electronics / repair

author: Bicurico
author_rank: Super Contributor
timestamp: October 30, 2021, 08:55:26 pm
content: Hi,I was at a flea market today and picked up a TI 58C. It came with charger and case and looked not too bad. The seller told me the calculator was not working, so at least he was honest.I paid a ridiculous 5 Euro, which I though was worth it even if the calculator was beyond repair.I expected the battery to have leaked and it was confirmed right away.I gave the PCB some cleaning and connected 3.6VDC from my power supply and saw the "0" pop up. But none of the keys were working, so I investigated further.Upon fully removing the PCB from the case I saw why the keyboard was not working: the leaked fluids had corroded the upper 3 rows of contact plates plus the centre wires. I expect the keyboard to be beyond repair, at least I wouldn't know where to get the metallic stripes with the cone shape that form the key contacts. Also, it seems pretty impossible to replace the contact wires.So my question is: does anyone have some tips and tricks on how to repair the keyboard?The calculator might suffer from bad RAM, which seems to be normal when the user tries to run the calculator with the power supply but without the battery pack in place.If the keyboard is not repairable, then I guess it is not worth trying to repair the remaining PCB. This is a shame, though, as the screen is working beautifully and the PCB seems OK, as well as the case itself. I will try to post some pictures later on.Cheers,Vitor

author: fzabkar
author_rank: Super Contributor
timestamp: October 30, 2021, 09:18:03 pm
content: Could we see some photos?This TI calculator has snap domes under each key:https://goughlui.com/2019/10/13/tech-flashback-repair-texas-instruments-sr-56-programmable-calculator/

author: Bicurico
author_rank: Super Contributor
timestamp: October 30, 2021, 09:29:46 pm
content: This site has a wonderful repair documentation and some pictures:https://www.hpmuseum.org/forum/thread-2334.htmlThe snap domes (didn't know the correct name for that) are seen here:They form several rows and each row is like a stripe of snap cones.They are held together by tape and snap over vertically laid out wires (which in my case are corroded, as well).I will attach pictures in a couple of days, as I won't be home.Regards,Vitor
Repair Tips:  Belkin Omni View PRO2 KVM:  VGA Horizontal Shadows - Page 1
Forum section: electronics / repair

author: MrCreosote
author_rank: Contributor
timestamp: October 19, 2023, 07:57:05 am
content: Any thoughts where to start looking?From old TV days, looks like horizontal scan voltage is being pulled down.It's the older VGA PS2 USB KVM

author: m k
author_rank: Super Contributor
timestamp: October 23, 2023, 08:39:27 am
content: So opposite colors, RGB -> CMY.Quite steady also.Is it the same if resolution is lower?

author: MrCreosote
author_rank: Contributor
timestamp: October 23, 2023, 05:01:29 pm
content: Excellent suggestion.Unfortunately didn't save the Paint project file so have to rebuild.Should get it done today and a reply.Just ordered a Gold ESR70 from Digikey (best price of all $93) and going to check caps in circuit.
Repair tips for 500W Audio Amp - Page 1
Forum section: electronics / repair

author: gjh
author_rank: Contributor
timestamp: August 29, 2023, 05:36:08 am
content: Any tips for repairing the following Audio Amp -https://www.megamusiconline.com.au/product/behringer-eurolive-vq1500d-15-inch-powered-pa-subwoofer-500-watt/It seems to be melting the ground wire between the onboard AC socket and PCB before blowing the fuse. Dont really see anything obvious inside besides a bulging electrolytic cap. I guess one of the amp/power transitors could be gone drawing more current. It's been awhile since I did circuit theory in school. Apart of purchasing a thermo camera (something Im thinking about for home leak detection) whats the best way to troubleshoot ?

author: Messtechniker
author_rank: Frequent Contributor
timestamp: August 29, 2023, 06:06:07 am
content: 1.) Measure each capacitor in-circuit.2.) Extract those which do not measure OK in-circuit.3.) The replace those which do not measure OK out of circuit.

author: gjh
author_rank: Contributor
timestamp: August 29, 2023, 06:46:00 am
content: Quote from: Messtechniker on August 29, 2023, 06:06:07 amWill give that a go. I have a ESR Meter as well

author: mengfei
author_rank: Regular Contributor
timestamp: August 29, 2023, 07:41:15 am
content: Isolate & TestIsolate the Power supply section from the AMP & the test the supply alone then you can go from therefor power amps usually it's the output or power supply problem. Sometimes some relays gets stuck tootake it out of the metal casing & just check the PCBA making sure that there is adequate GND

author: Messtechniker
author_rank: Frequent Contributor
timestamp: August 29, 2023, 12:37:55 pm
content: When testing power supplies on their own,dont forget that some will need a load.

author: knudsenuk
author_rank: Contributor
timestamp: August 31, 2023, 01:46:25 pm
content: Agree, isolate the psu first, emulate the psu with a bench psu (with current limiting) connected to the amplifier module and also measure the DC offset on the output which I suspect will be skewed heavily in favor of one supply rail, giving you an indication of the likely failure, also one rail will be drawing much more current from the supply. Obviously if it is a genuine 500w then it it may be hard to the operating voltage from a bench psu.
Repair Toshiba A215-S4767 Random Crash Video Corruption - Page 1
Forum section: electronics / repair

author: joystik
author_rank: Contributor
timestamp: May 27, 2019, 01:27:27 pm
content: Hi.I have this Toshiba A215-S4767 for some time now. It is now crashing randomly, but frequently. Sometimes while idle, and sometimes working. Mostly when in windows, only a couple times before finishing loading windows. Shows vertical color lines or sometimes screen goes slowly to black or white.I reinstalled the OS, windows 7 pro, no change.I disassembled it, cleaned it, cleaned all cards, memory, wifi, modem. Cleaned fans and reapplied tim to all chips.No change.Checked for corrosion on any components, but none show visible signs of corrosion or failure.I measured all voltages before and after crash. I noticed 1.8V goes to 0.7V after crash, but Im stuck there. PWM input is 18.9V(charger) looks fine.Could you please advise what to check for next?Thanks in advance.

author: Arjunan M R
author_rank: Regular Contributor
timestamp: May 27, 2019, 02:25:53 pm
content: I think it is the problem with the display driver.Connect an external monitor and try again..

author: joystik
author_rank: Contributor
timestamp: May 27, 2019, 03:35:52 pm
content: Arjunan, Thanks for your reply.I just made a memory minidump and got a stop error at ntoskrnl.exe 0x00000124.After looking this up it appears it could be an overheating problem which is was characteristic of AMD processors from that time. Turion X2.Ill put some new TIM and try again.Will update soon.

author: Arjunan M R
author_rank: Regular Contributor
timestamp: May 27, 2019, 03:56:43 pm
content: Quote from: joystik on May 27, 2019, 03:35:52 pmWhat do you mean by TIM.Asking because I don't know.

author: joystik
author_rank: Contributor
timestamp: May 27, 2019, 04:44:21 pm
content: Quote from: Arjunan M R on May 27, 2019, 03:56:43 pmTIM = Thermal Interface MaterialIt refers to thermal grease, thermal pads, or thermal paste of any kind. The type that goes between the heatsinks and the CPU, GPU and other chips.

author: Arjunan M R
author_rank: Regular Contributor
timestamp: May 27, 2019, 04:48:34 pm
content: Thanks, I didn't know that.

author: joystik
author_rank: Contributor
timestamp: June 06, 2019, 10:07:33 pm
content: Update:Still crashing randomly. Not sure whats causing it.Same symptoms as before.Enviado desde mi iPhone utilizando Tapatalk
Repair Trimble AG-372 / No response from MPU - Page 1
Forum section: electronics / repair

author: Gabrowsk
author_rank: Newbie
timestamp: August 16, 2024, 04:00:09 pm
content: Hello guys, First time posting here and english is not my first language sorry for the typos.I’m working on a GNSS receiver repair that’s completely frozen and unresponsive. I’ve conducted some tests on the board and have the following observations:All power supplies are delivering the correct voltage.All crystal oscillators are functioning correctly.I didn’t find any short circuits on the board.I suspect the issue might be with the MPU on the board, an MPC5121YVY400B from NXP. When I try to flash a new firmware version, the board doesn’t respond. I’ve tested both RS232 ports and both CAN ports on the device, but there’s no response. I’ve also checked both the RS232 and CAN communication circuits by injecting a logic signal into the port and measuring with an oscilloscope. The signals reach the test points beneath the MPU correctly.Does anyone have any tips on how to confirm if the problem is indeed with the MPU? If that’s the case, I would need to purchase a machine for re-chipping, so I need to be certain.Another possibility is that the issue could be with the NOR flash memory connected to the MPU, but I also don’t have the equipment to test these components.Does anyone have any ideas on how to proceed?
Repair usb-c headphones connector - Page 1
Forum section: electronics / repair

author: Acer444
author_rank: Newbie
timestamp: September 07, 2023, 08:28:22 pm
content: My headphones stopped working because of broken wires, I took apart the USB-c connector to resoldier wires but accidentally scratched off the markings on PCB while removing compound and now I have no idea how to soldier 5 wires back in the correct order. Any ideas? The original headphones are for Huawei mate 20 pro smartphone.

author: u666sa
author_rank: Frequent Contributor
timestamp: September 08, 2023, 04:12:40 am
content: You gotta take out the rest of white gue and ring it to the actual USB-C connector, see what is what.

author: DavidAlfa
author_rank: Super Contributor
timestamp: September 08, 2023, 06:25:07 am
content: Nah, these headphones are way more elaborated,they have they own DAC, I had them.

author: u666sa
author_rank: Frequent Contributor
timestamp: September 08, 2023, 11:18:39 am
content: If you take off the gue, you will see where the ground is, 3 of them, and where the mic is, left right is going to be hit or miss.

author: u666sa
author_rank: Frequent Contributor
timestamp: September 08, 2023, 11:27:22 am
content: There is another approach. Find 3 grounds. Then find find left, then find right, by soldering and trying to play music. The remaining one would be mic.

author: wasedadoc
author_rank: Super Contributor
timestamp: September 08, 2023, 01:07:52 pm
content: If DavidAlfa is correct that these headphones have their own DAC then there are no analogue signals on the connector and all the above posts by u666sa can be ignored.

author: DavidAlfa
author_rank: Super Contributor
timestamp: September 08, 2023, 01:40:14 pm
content: Yes they do, the DAC is in that small board!

author: amyk
author_rank: Super Contributor
timestamp: September 08, 2023, 01:41:11 pm
content: Plug it in, play test tone (different frequencies on left and right channels), probe with scope to find the left and right channels and ground.
Repair Vacuum motor Samsung VR9000 SR20H9050U - Page 1
Forum section: electronics / repair

author: ornea
author_rank: Unknown
timestamp: February 03, 2021, 04:04:46 am
content: Davo the robot vacuum sucked up some bathroom floor water.Initial measurements indicated close to short circuit on the +/- input to the motor (VCM-200CLDA).Found 2 mosfets shorted so replaced. It ran for about 2 meters then a puff of smoke and stopped.Found additional failed mosfets so I have replaced all 6. (3 x N-ch 3 x P-Ch)Before pressing back into service I scoped the gates of the mosfets but they are not what I expected. See attached.Does this look normal. I was expecting something else. I have a 15ohm resistor in series with the 21.6v feed to limit current and limit damage. From the trace it appears it peaks around 300mA, I was expecting more. The resistor does get warm. (Very hot before I replaced the mosfets)Happy to provide any additional info or pics. I am guessing what info to provide. I am hoping to make sure all is ok before I remove the limiting resistor.There are 6 wires in the cable harness. I am assuming 2 for power and the remaining 4 are status and control signals. Can I assume that the mosfet drive sequencing is generated on the motor PCB and not from the main controller board. Is that typical?The pink trace is the volts across that resistor, the other traces are connected to the gates of the three N-CH mosfets.Warmly welcome and suggestions, tricks and advice.Image showing the hookup

author: ornea
author_rank: Unknown
timestamp: February 03, 2021, 04:26:52 am
content: Have attached the Gate traces to the P-Ch mosfets in the hope it may prove useful.
Repair Xiaomi Mi Smart LED Desk Lamp Pro - Page 1
Forum section: electronics / repair

author: davidbo
author_rank: Newbie
timestamp: November 21, 2022, 07:33:21 pm
content: Hi everyone,I recently bought a Xiaomi Mi Smart LED Desk Lamp Pro for my desktop. To goal is to use it for circadian lightning (changing between white and cold warm depending on the position of the sun). The lamp has an ESP32 chip for connectivityI changed the firmware of my Xiaomi Mi Smart LED Desk Lamp Pro to EspHome to make it compatible with my Home Assistant automation. Flashing went fine but it seems something got damaged along the wayThere are two different LED strips in the lamp - a cold white and a warm white one and they get mixed depending on the configured light. The power supply delivers 12v with 1A and the LEDs run on 24v. The cold one works just fine - I can adjust brightness and adapt to the overall light settings.The warm one works sometimes. After turning it on it usually works for some time after it starts blinking and then turns off. The voltage for the LEDs drops back to 12v. When I configure the lamp via the rotary encoder it works just fine. As soon as I release the knob (touched by hand) the light stops working again. I checked if the encoder casing is connected to something via my multimeter and I could find anything. The circuit has a similar behavior if I place my finger close the circuit. When the LEDs were off they started to blink rapidly.This is the PCB.The right-hand side of the PCB (looking from the top) seems to be responsible for the warm white LEDs. I assume on the PCB is some kind of step up converter and measured the output voltage across C22.On the back are some pins but unfortunately, I ripped them off by accident. That's why I had to solder to the ESP32 pins directly to flash them and they look not as nice as before. I checked them and there are no short circuits to my knowledge.I have a few questions:- Since touching the rotary encoder changes the behavior I assume it changes some capacity value on the board. Is worth trying to replace them?- Might the rotary encoder itself be the issue?- What else can I do to dig deeper into the issue?- What can I do to identify other components? e.g. Q6 which seems to be some kind of transistorAny help is appreciated!I only have a multimeter to measure any data points
Repair Yaesu FT901 DM suggestions/recommendations - Page 1
Forum section: electronics / repair

author: LFibich
author_rank: Newbie
timestamp: December 29, 2020, 05:04:31 am
content: Looking for repair /suggestions as to what area and/or components to look at. I had a unit with a bad transformer and it burned - met a person on line and he offered a chassis with a good transformer that had been cannibalized for the boards and removable components - I don't know what it was cannibalized - but the unit and wiring really pristine... so I used ALL the boards and removable components from the unit I had - checked them before and again when assembled in this 'new' unit -- I have another unit that works - and ALL boards worked fine. OK when completed the 'new' unit display blinked and nothing worked -- traced the difficulty to a voltage regulator transistor and replaced it -- Unit works PERFECTLY on receive; and perfectly on AM; CW; and FSK - BUT no power output on SSB (upper and lower); and FM. Studying the schematic I thought surely the diodes on/around the mode switch (that appear intimately involved in SSB) would be the cause -- checked all (6) and they are fine. Also 3 other diodes wired on the board connectors - ok but not really involved. ON SSB section - audio monitoring works, relay's click/work; vox works - all appears OK except no power out put and of course minimal IC.. Looking for suggestions as to where to look/check... Since ALL the boards work and removable components HAS to be something on the chassis - perhaps the reason it was cannibalized in the beginning??? Any and all suggestions most appreciated... 73 Larry LFibich@sbcglobal.net W6EF

author: m3vuv
author_rank: Super Contributor
timestamp: December 29, 2020, 07:43:10 am
content: does it get any drive to the 12by7 driver valve?

author: bob91343
author_rank: Super Contributor
timestamp: December 29, 2020, 07:46:42 pm
content: Break out the oscilloscope and track the signal, as hinted by the above post.
Repair Yokogawa Universal Leak Tester 322610 Burnt Resistors - Page 1
Forum section: electronics / repair

author: generalheater
author_rank: Newbie
timestamp: June 10, 2021, 03:38:32 am
content: Please help. I would like to replace the burnt resistors on my Yokogawa Universal Leak Tester 322610. Affected resistors are R4, R5 and R6. I need to know the resistor values. Appreciate if you could send also photos for reference. Thanks.

author: PE1RQF
author_rank: Newbie
timestamp: June 18, 2021, 12:17:58 pm
content: Original is R3=500 Ohm, R4=500 Ohm, R5=200 Ohm,R32=200 Ohm, R6=200 Ohm, R7=200 Ohm, R8=100 Ohm, R9= 90 Ohm, R10=10 OhmThis is from the schematic I found.SuccessErik