hybridfree/eevblog-posts huggingface dataset:
Faded LCD display Weatherstation - Page 1
Forum section: electronics / repair

author: martfoxy
author_rank: Regular Contributor
timestamp: June 25, 2024, 01:28:49 pm
content: Is there anyway of restoring the display on a LCD weatherstation (Auriol) - it has areas that are darker? Is it the backlight or the display itself?

author: jzx
author_rank: Regular Contributor
timestamp: June 27, 2024, 05:19:30 pm
content: I dont know if is an effect of picture, but seems that some segments are missing. You can check / clean the zebra strips, that can cause all screen to be dark or low contrast.
Failed attempt at hardwired headphone jack. - Page 1
Forum section: electronics / repair

author: kingoftaurus
author_rank: Contributor
timestamp: May 22, 2023, 02:23:20 pm
content: Hey all!I purchased an HDMI video stick "Neumi Atom Cast" and due to some stealthy requirements, I needed to eliminate the plug in IR sensor.I removed the SMT "headphone" jack that the sensor plugged into and hardwired the IR sensor directly to the board.Long story short, the IR sensor does not work.Any ideas on what's going on here?(Ignore the terrible wires, I cut them thinking I reversed polarity and reattached them afterwards)

author: wasedadoc
author_rank: Super Contributor
timestamp: May 22, 2023, 03:06:55 pm
content: Do you measure in the region of +3.3 to +5.5 volts on the red wire with respect to the black one?

author: kingoftaurus
author_rank: Contributor
timestamp: May 22, 2023, 03:10:48 pm
content: I measure 2.78v

author: wasedadoc
author_rank: Super Contributor
timestamp: May 23, 2023, 07:33:08 am
content: What voltage on the white wire and does it change when you push and hold one of the buttons on the remote?

author: Psi
author_rank: Super Contributor
timestamp: May 23, 2023, 07:37:37 am
content: That footprint has 5 pads, so almost definitly has a switch built in to detect when something is plugged into the jack.Maybe the circuit was using the switch to enable/disable the IR somehow.And without that link it won't work.See if you can figure out how that headphone jack worked and which contacts were the plugin switch/switches.Then replicate that so its the same as having the jack plugged in.

author: wasedadoc
author_rank: Super Contributor
timestamp: May 23, 2023, 08:44:08 am
content: Quote from: Psi on May 23, 2023, 07:37:37 amThat is a possibility though the typical 3 pole socket with 5 pins has switches which open when the plug is inserted. That would be equivalent to leaving those PCB pads as they are.

author: kingoftaurus
author_rank: Contributor
timestamp: May 23, 2023, 07:53:11 pm
content: I thought the same thing about the switch. I will get back to you about the white wire.I purchased another one so we will get the answer for sure.The old jack was mutilated taking it off the board unfortunatelyWhite to black is .595 v no change when remote pressedUpdate:New device came in.Bottom two pads are always connected. Top two pads are switching, (open when plugged in).Black and white are reversed.Hope it still works...(It works now
Failed backlight Agilent U1252B - Page 1
Forum section: electronics / repair

author: Lorenzo_1
author_rank: Regular Contributor
timestamp: August 12, 2022, 02:22:10 am
content: Back light on my Agilent U1252B no longer turns on. It's only a year or so old. Everything appears to work OK. Played with Menu options to change backlight timer and also Reset to factory defaults. Also removed/reinstalled batteries after power on with no battery installed (presumed this would drain any reserve charge in caps). No effect. Simply beeps when I press backlight button. Has anyone encountered this? Is it a known problem or is there another fix I might be missing? It's under warranty but a nuisance to ship back and be without.
Failed ZHQ microswitch in hedge trimmer - Page 1
Forum section: electronics / repair

author: smuudge
author_rank: Newbie
timestamp: July 10, 2019, 07:56:07 pm
content: Hello, I am trying to repair a Eckman hedgtrimmer. I have found the fault that appears to be the ZHQ microswitch (see attached pix).I am somewhat of a novice with micro switches but to confuse matters this has 2 mini buttons that are triggered by the plastic button in the housing. When I press one of them the unit works, when I reinstall the plastic button and casing (which presses both of them together) it does not work. I assume a failed switch?Also why are there 2 buttons on the micro switch! is this a fail safe?And also can anyone recommend a suitable replacement I might be able to get in the UK/Europe as I cannot find ZHQ switches for sale in the UK. It is a ZHQ ZQ7 12/1.Thanks in advance!

author: CJay
author_rank: Super Contributor
timestamp: July 10, 2019, 09:16:49 pm
content: It looks like a dual pole microswitch, I.E. it switches live and neutral.So it completely isolates the mains from the motor when off and yes, I suppose it's unlikely that both poles fail together.Something like this perhaps?https://www.ransomspares.co.uk/parts/hedge-trimmers/flymo/switch/419702.htm?gclid=CjwKCAjwmZbpBRAGEiwADrmVXkqDLdm0Ke6NiH3nncOd_XKlPwbhzO_uS9tQHQ0ABQYtgAhBz8aKfRoCafQQAvD_BwEOr perhaps this:https://www.toolsandpartsdirect.co.uk/switch-ph5551-1?gclid=CjwKCAjwmZbpBRAGEiwADrmVXuvGh-KpEX6k5gFi2Kh0QyQPZbAfUHE-H-KbUO_DUZV6UVYB3QodjxoCyjkQAvD_BwE

author: Magicshark
author_rank: Newbie
timestamp: May 29, 2020, 01:13:50 pm
content: Quote from: smuudge on July 10, 2019, 07:56:07 pmI don't think both switches fail together at the same time.
Fairy Lights & Battery Acid on the Electronics - Page 1
Forum section: electronics / repair

author: jonovid
author_rank: Super Contributor
timestamp: January 04, 2025, 10:54:57 pm
content: battery operated fairy lights for a childs bedroom. hanging from the ceiling once forgotten about.the 4 AA cell 6 volt battery pack leaked acid over the pcb see-image.I made a repair using a 5 volt AC plug pack power supply from an old modem.replacing everything except the fairy lights and adding a longer cable.what I would like to know is the original intended purpose of the microcontroller in a simple 2 wire circuit.other than just a timer. as any flickering of a single circuit cluster light would not be that pleasant.as most Christmas lights use 2 or 3 strings in parallel circuits to get a pleasant twinkling effect.

author: Swake
author_rank: Frequent Contributor
timestamp: January 05, 2025, 11:07:16 am
content: As you mentioned, this thing is just a timer to save some battery capacity. Eventually it can be a dimmer that reduces intensity over time to make it a 'kids sleep lamp'.After a good clean this might still work. It is a very simple schematic. Rinse it with water and a eventually a mild detergent. You might want to use a mild brush like a toothbrush. Dry it well before powering up. Make sure there is no moisture under the chip. Measure all the traces to check them.J3Y is probably a S8050 transistor. See pic borrowed from the internet
Fake Dallas DS1486 has just one battery -- photos included - Page 1
Forum section: electronics / repair

author: rodd
author_rank: Regular Contributor
timestamp: September 29, 2020, 06:34:56 pm
content: I bought a couple of DS1486 to practice my Dremel skills so I could use them on the "real one" installed on MY TDS784D.I have seen some photos of the real chip carved to expose the batteries and there were two of them.To my surprise the "new fake" one has just one.I have attached the photos here for reference.If that is the new "state of the art" it will be easier to confirm that the chip is fake probing it with a strong magnet.Roger

author: youngwug
author_rank: Contributor
timestamp: September 29, 2020, 07:08:15 pm
content: Is the one shown above positive(+)?Does it stick to pin 1?

author: rodd
author_rank: Regular Contributor
timestamp: September 29, 2020, 07:39:46 pm
content: I lifted the battery now. The positive is on the bottom.I could not find continuity to any of the pins to the battery, but when I carved a little bit more to try to find the connection to the pins this green stuff appeared.Corrosion?I have attached two more photosThe positive terminal of the battery goes to the greenish part of the left of the photo

author: james_s
author_rank: Super Contributor
timestamp: September 29, 2020, 07:51:49 pm
content: I opened up a fake Dallas chip, I forget exactly which it was but I found that same looking yellow wrapped battery. I started xraying Dallas chips and found that the fakes are easy to spot. Of all the ones I've bought from China a few were genuine but old used parts that had been sanded off, blacktopped and printed with new labels, one of those even had data on it already, or counterfeit parts that are completely different. Not a single one of the counterfeit parts worked correctly though not all had the same problem.

author: fzabkar
author_rank: Super Contributor
timestamp: September 30, 2020, 05:03:23 am
content: This might be a better solution:https://www.eevblog.com/forum/repair/dallas-ds1486-and-ds1250-replacement-designs/

author: Berni
author_rank: Super Contributor
timestamp: September 30, 2020, 05:11:13 am
content: Quote from: fzabkar on September 30, 2020, 05:03:23 amI made made Dallas NVRAM replacements using Cypress FRAM chips with parallel interfaces. You get 100 year data retention with no battery to go bad.Running them in a HP 3458A just fine.

author: james_s
author_rank: Super Contributor
timestamp: September 30, 2020, 06:58:07 am
content: Quote from: Berni on September 30, 2020, 05:11:13 amI did that too but it didn't work in a Tektronix power supply. The basic functionality worked fine but there was part of the calibration routine that would fail every time. I believe it has to do with a quirk of these FRAM chips in the way the address is latched, you have to de-assert the CS input between each address, or something like that. You are dependent on how the firmware in the device you're trying to retrofit was written in whether it will work or not.
Faluty computer power supply - Page 1
Forum section: electronics / repair

author: dlsa
author_rank: Newbie
timestamp: October 05, 2022, 09:45:54 pm
content: Hello Community,I have a NeXT Cube (a 90's computer) with a faulty power supply. When I power on the computer, it stays up or about 4 seconds and then shuts down again.Is this a common fault ? What part of the power supply should I be looking at first ?I did a visual inspection, and noticed nothing, capacitors are not leaking, nor bulged.Thanks in advance,Regards

author: james_s
author_rank: Super Contributor
timestamp: October 06, 2022, 02:26:47 am
content: Capacitors are the most common problem, although it's possible something is overloading it and causing it to shut down. Most of the time when capacitors fail there are no visual signs of problems, leaking/bulging happens only when they are REALLY bad.
Fan für an Laptop? - Page 1
Forum section: electronics / repair

author: Lord of nothing
author_rank: Super Contributor
timestamp: April 26, 2023, 07:07:28 pm
content: Hey everyone. I put out of an Tablet that I refurbish an Fan I could not find a new replacement.The say MCF-S4540AM05. Mine also smell disgusting smoked.Any idea where to get them from?Thanks

author: fzabkar
author_rank: Super Contributor
timestamp: April 26, 2023, 08:11:41 pm
content: https://dstockmicro.com/en/cpu-cooler-fan/12257-fan-mcf-s4540am05-for-fujitsu-stylistic-st6012.html

author: Lord of nothing
author_rank: Super Contributor
timestamp: April 26, 2023, 08:21:01 pm
content: Quote
Fan replacement Lecroy Xs scope - Page 1
Forum section: electronics / repair

author: Momchilo
author_rank: Regular Contributor
timestamp: July 08, 2022, 07:21:43 pm
content: Hi,I have a Lecroy Wavesurfer Xs scope with two of those fans: Young Lin Tech DFB701512H. Here is the datasheet of the fan:http://www.ymmicro.com/files/PDF/DFB701512H(AUTO%20START).pdfThe bearing of one fan is no longer okay and makes noise. So I want to replace the fans. But it is impossible to find a fan with similar ratings. I can buy exactly this model again atAliexpressand other shady shops. But the fans are quite loud. So I hope there are better options.The ratings from the datasheet of the original fans:Voltage: 12V DCOperation voltage: 10.8-13.2VCurrent: 0.19APower: 4.2WSpeed: 4600RPMAirflow: 32.39CFM / 55m³/hAir pressure: 3.65mmH2O / 0.143 inH2ONoise: 37dBConnector: 2pinsDimensions: 70x70x15mmThe volume flow should not be lower because the fan cools the power supply and it is known that the power supplies are already thermally very heavily loaded in those models. Even if price is not an issue, I can't find a compatible fan with similar ratings in this size. As an example the EBM Papst 712F:https://de.farnell.com/ebm-papst/712f/axiall-fter-70x15mm-12v-s/dp/9600841The speed is higher and yet the airflow is much lower.Do you think the values in the data sheet of the Chinese fan are simply not true? Because something must be wrong. The 4.2W is printed on sticker of the fan and it doesn't match 13.2V*0.19A=2.5W at all.Maybe someone else knows someone good alternative?Best regardsMomchilo

author: heize0
author_rank: Contributor
timestamp: March 07, 2025, 01:12:59 am
content: I suggest Delta AFB0712HB. It consume less power but has more a little air flow.

author: benj38
author_rank: Frequent Contributor
timestamp: March 07, 2025, 12:28:10 pm
content: Quote from: Momchilo on July 08, 2022, 07:21:43 pmLast time I checked, there was no update to the formula of DC power equal voltage times currentYes, the datasheet is definitely not to be believed. Why don't you measure the current through the fan yourself? I bet it is going to be pretty close to the true specs even though the bearing is a bit bad.It would not be the first time that a fan's datasheet gives far superior performance specs than what the reality is. I only truly believe fan specs when they come from very reputable manufacturers like EBM Papst or Panasonic.Finally, in my experience, if you can not find a reputable fan of a standard size, with the airflow and static pressure specs you are looking for, then such a fan does not exist, no matter what the inferior brands claim.
Farnell B30/10 Power supply 110v or 200v ? - Page 1
Forum section: electronics / repair

author: diegooo1972
author_rank: Newbie
timestamp: July 19, 2019, 04:21:41 pm
content: Hi guysI'm quite new here and noobish. I hope someone can help me.I try to understand if this power supply is 110v or 220vOf course there' s nothing about the input voltage anywhere. I tear it down and posted the photo herehttps://imgur.com/a/h3xFl3cThe fuse just says 10A and no voltage. The plug was missing and before to put a new plug I was trying to be sure about input voltage.This power supply has been left to my father from my grand father. And now the head of my father is not working properly anymore so he can't help me.There are also some specifications herehttp://www.testequipmenthq.com/datasheets/FARNELL-B30-10-Datasheet.pdfTo go on looking around the transformer I need to start desoldering everything and at the moment I don't fell comfortable doing so.I hope that I am in the right place on the forum and also hope not to bothering you. I just try to learn if possibleExcuse if this is a noob question.Thank in any case.

author: JFJ
author_rank: Regular Contributor
timestamp: July 19, 2019, 06:51:07 pm
content: Please see Fig. 1, in the Farnell "B Series" Power Supply Instruction Manual, for details of the transformer connections for different input voltages:http://rtellason.com/manuals/FarnellBSeriesPowerSupply.pdf

author: diegooo1972
author_rank: Newbie
timestamp: July 19, 2019, 07:23:23 pm
content: Thank you soo much.I never had something like this to select 220v and 110v and I tought this was too old to find a manual.Lack of experience and din't search enough I think.I'm very gratefull.
Farnell type C1 power supply - Page 1
Forum section: electronics / repair

author: drgius
author_rank: Newbie
timestamp: February 13, 2022, 01:05:46 am
content: Hello everyone,does anyone have any service manual for the FARNELL C1 Power supply?I brought this power supply home, to sit beside me on my workbench, because it used to be my grandfathers (never seen him using it tho). When plugged in power supply has constant CI (current limiting) light on. I have opened case and couldn't find anything obvious.before starting this new thread I tried to search for any info that is already posted and found this threadhttps://www.eevblog.com/forum/repair/farnell-c1-bench-power-supply/, unfortunately the link provided to collection-achivist is not working for some reason and I sent pm to the SgtTech but his last activity was in 2020any help is greatly appreciated!I have uploaded few more pictures that shows boards insidehttps://imgur.com/a/cOYSL7h

author: bob91343
author_rank: Super Contributor
timestamp: February 13, 2022, 01:51:56 am
content: Many of these power supplies have a protection diode across the output. I bought one at a swap meet for $2 and sure enough, replacing the shorted diode fixed it.

author: FIXITNOW2003
author_rank: Regular Contributor
timestamp: February 13, 2022, 05:05:36 pm
content: I have fixed some TTi PL320's with shorted diodes across the output

author: drgius
author_rank: Newbie
timestamp: February 13, 2022, 09:50:28 pm
content: thanks for your inputs Fixitnow2003 and Bob91343, I will try to probe inside and basically check every single diode to see if it's blown or notedit:I was testing diodes with my fluke 115 and I thought they were fine because meter indicates around 0.6v drop , but not I have the benefit of the doubt. Can someone talk me through how to test Zener diodes with DMM? Google suggested me few websites and they all basically says that DMM in resistance mode should read relatively low resistance on forward bias and in Megaohms in reverse bias. I am now checking Zeners made by hughes HS2051 and getting both ways.... Is this an indication of a bad Zener diode? if I go to diode mode it shows 0.6v forward bias and around 1.3v reverse bias.I have attached few pictures to show what I mean.

author: BrokenYugo
author_rank: Super Contributor
timestamp: February 14, 2022, 03:56:04 pm
content: To properly test a zener you really need it out of circuit and you need some current limited source of voltage higher than the zener voltage (a DMM is good for like 3 volts). You also need to know what the zener voltage is supposed to be.It was suggested you check one diode, they told you where it was, across the output, follow the output + and - back until you find a power diode between the two. It sounds like it may be functional otherwise, hence the suggestions to check the output diode which is often damaged by user error.
Fault PTC - help identifying replacement - Page 1
Forum section: electronics / repair

author: 5m3g_head
author_rank: Newbie
timestamp: February 18, 2023, 09:34:08 pm
content: Hi , I was wondering if anyone could help me identify a part, or recommend a suitable value to replace with.Recently my beard trimmer started to display a fault where it only ran for 30sec before grinding to a halt. I suspected the battery as the unit is old. However after replacing the cell, the device had the same issue.After poking around of a while I discovered that the PTC right near the positive to the motor was faulty. I would like to replace it, however Im not experienced enough to know what value to use.The device is a Remingtion MB6550 and it runs a single 18500a Li-ion cel.I've attached a photo of the faulty component, does anyone have any suggestions for me ?

author: Original
author_rank: Contributor
timestamp: February 18, 2023, 11:00:35 pm
content: I have seen this beforehttp://www.alpha-top.cn/prduct_detail.aspx?id=419

author: R-1125F
author_rank: Regular Contributor
timestamp: February 18, 2023, 11:16:02 pm
content: This looks like the correct part.https://jlcpcb.com/partdetail/897936-JK_SMD1210200/C841187

author: 5m3g_head
author_rank: Newbie
timestamp: February 19, 2023, 05:08:09 am
content: Two Thumbs up ! thank you both for your help.. I get one ordered.Cheers.

author: floobydust
author_rank: Super Contributor
timestamp: February 19, 2023, 05:13:21 am
content: Also note the PTC might be okay, it's that the motor current has gone high due to mechanical issues or lack of lube.I use oil 20W for the motor, and molylube in the mechanism. PTC fuses do get softer everytime they trip.

author: 5m3g_head
author_rank: Newbie
timestamp: February 19, 2023, 10:08:55 am
content: Thank, I'll make sure I clean and lube it up when I replace the PTC.

author: R-1125F
author_rank: Regular Contributor
timestamp: February 19, 2023, 01:50:01 pm
content: You might want to test the circuit before ordering the part. I don't think it would hurt to jumper the PTC for testing.LCSC carries the part.

author: 5m3g_head
author_rank: Newbie
timestamp: February 20, 2023, 05:59:21 am
content: Cheers, that's exactly how I tested it.Jumped the PTC and shaved my beardPretty confident the PTC will fix it, but I'll still give it a good clean and lube.

author: 5m3g_head
author_rank: Newbie
timestamp: April 01, 2023, 09:49:20 pm
content: For anyone following along at home. I replaced the PTC with the one linked here, lubed the blades and the shaver is in A1 working condition.I have used it 5 times since, and charged it.. all good.Thanks all on here for the help.

author: floobydust
author_rank: Super Contributor
timestamp: April 01, 2023, 10:03:46 pm
content: That's great, shaver prices are ridiculous nowadays. Remington fuse Alpha-top SMD1210-200 rated 6V 2A hold 4A trip, 8A 1 sec.Same as Littelfuse 1210L200 or Bourns MF-USML200/6 is close.
Faulty 8V standby rail on Bang & Olufsen MCMXCIV CRT TV - Page 1
Forum section: electronics / repair

author: am241
author_rank: Newbie
timestamp: December 21, 2024, 01:39:32 am
content: Greetings,I have recently aquired a Beovision avant 28 CRT TV from B&O. Unfortunately, the unit is in a nonworking condition with not even a standby light. However, there is some slight coil whine when the TV is powered. I have found a service manual, and using the missing standby light as a clue, I measured the 8V standby (8VSB) rail on the PSU, which only gave me a reading of 2.3V (see attached diagram). SSupplying 8V to this rail by external supply at least lights the standby LED, but I am not sure how to fix it. No components appear to be damaged or burnt on the power supply PCB.I am not very experienced with diagnosing electronics, so any help and/or pointers, however small, will be greatly appreciated.Thanks.
Faulty Andonstar ADSM302 microscope, firmware required? - Page 1
Forum section: electronics / repair

author: Ivan_s_Lab
author_rank: Newbie
timestamp: November 16, 2020, 12:38:50 am
content: Greetings I have a Andonstar ADSM302 microscope which served me quite well until yesterday. I had a lot of work to do and I left my lab powered off for about a month. Yesterday I switched on the microscope and it is stuck on the Welcome screen. I tried the reset button, power button and several USB supplies, but the result was the same. On the back of the board there is a 25Q32 Flash which I believe contains the Firmware. I tried finding the firmware online but no luck there as well. If someone has this microscope and a programmer I would be very grateful If you can generate a HEX or BIN file of that chip so that I can try to revive my unit. Also any other solution is welcome as well.

author: fzabkar
author_rank: Super Contributor
timestamp: November 16, 2020, 09:04:03 am
content: I would read your chip and look for a checksum.

author: RAPER
author_rank: Contributor
timestamp: March 08, 2022, 09:45:32 pm
content: Hello, I have the same problem with my adsm302 too. Do you have a bin / hex file for this microscope?

author: SSaimor
author_rank: Newbie
timestamp: March 14, 2023, 07:02:19 pm
content: Hello. You did it? I am also in need.Quote from: RAPER on March 08, 2022, 09:45:32 pm
Faulty ATX PSU intermitten power down Clr Master V750 semi-modular RS-750-AMA-G1 - Page 1
Forum section: electronics / repair

author: FrankE
author_rank: Regular Contributor
timestamp: April 02, 2020, 04:07:04 am
content: I fiddled about with the energy efficiency in the UEFI BIOS several weeks ago and a couple of weeks later my PC kept powering down in use or when going into sleep.It could stay on for over a day or ten minutes then there'd be a click from the machine and it would power down.I'd have to switch off the PSU, waith for the motherboard LEDs to extinguish then it could be powered on again. I assume the click was from the ATX PSU but I'm quite hard of hearing.The warranty expired (bought 2013) so I opened it up, vacuumed it.Could anyone point me top a service manual or schematics please.I've found one component frazzled. It's an SMD R or C one of two components off pin 9 on the edge of the underside (solder side) of the board, off the PS233 '4-Channel Secondary Monitoring IC With 4-Channel OCP And an Additional OTP'https://datasheetspdf.com/pdf-file/666047/SiliconTouchTechnology/PS223/19 OTP Over temperature protection input pinThe surviving component is an 822 resistor 8.2k resistor. It's not that it's the vapourised one to the right of that when board is solder side up and modular sockets facing.I'l need to figure from there what caused the passives on the OverTemp pin to blow, if it wasn't the build up of dust.. If it holds up I'll maybe do some recapping if I've the right components at hand.The solder side is quite messy, I wondered if there was a short, unless it's just bad lead free wave solder.I can try to photograph it but I don't have a fancy camera that does macro and I'm using a Chromebook as my PC until I get a PSU delivered (order still sitting at 'waiting to pick' due to high demand).Many thanks
Faulty auto mode switching (Aneng ST212) - Page 1
Forum section: electronics / repair

author: Traceless
author_rank: Frequent Contributor
timestamp: October 02, 2022, 05:21:42 pm
content: Hi everyone,I have an Aneng ST212 AC/DC clamp meter here, with a faulty automatic measurement mode detection. If the meter is switched on it should stay in "auto" mode and once one starts to conduct a measurement it should automatically select the appropriate mode (voltage, resistance, continuity, etc.). However if I turn the meter on (no leads attached), it briefly goes to "auto" mode, then switches to resistance cycles through the ranges (Ohms, kOhms, MOhms), briefly switches back to auto, and then the cycle repeats. My first idea was that there might be something wrong with the isolation of the inputs - so that open circuit looks to the meter like a resistance measurement. This does not seem to be the case. If I select ranges automatically resistance measurements work pretty precise.Mode selection seems to be performed by the relayHFD31/2.4-L2S, which audibly clicks whenever the meter changes mode. Does anybody have experience/hints on how to troubleshoot auto mode switching?Edit: The manual DCA reading seems to be way off as well, the meter shows 0.7A without any current flow being present. Maybe just a faulty chip?
Faulty BK precision 4086 repair  - Page 1
Forum section: electronics / repair

author: Legend18s
author_rank: Newbie
timestamp: June 19, 2025, 05:23:54 pm
content: I need help repairing this BK precision 4086 function generator. The scope works outputs a clean signal below 4vpp but as soon as I turn the amplitude any greater the signal distorts and becomes unusable... until 13 Vpp after which the signal becomes clean once again but this time the amplitude is wildly inaccurate 3 Vpp on the scope for 20 Vpp on the generator. Unfortunately I have emailed BK precision about this issue and they told me that they do not have a service manual or schematics for this model.I do know that after 4vpp the signal path (internally) is switched by a relay (I can hear it click every time I raise the amplitude from 4Vpp to anything greater and then again if I keep raising it to 13 Vpp) but due to the lack of schematics and heatsinks (which for the life of me I can't remove) on what I assume are the NPN transistors for the amplifiers, I don't even know where to start checking.If anybody has repaired these before or if they have a schematic for these and could offer any assistance than that would be great.Thanks and best regards,Legend.
Faulty Brymen (857?) - Page 1
Forum section: electronics / repair

author: TroelsM
author_rank: Newbie
timestamp: February 22, 2024, 07:43:23 am
content: Hi Guys.First time poster, longtime watcher. Hope this is the right place to post.I'm a experienced electronics engineer, but sadly with lack of time (and maybe talent)I rescued an Brymen from the dump at work and I'm pretty sure its a 857 model.Visually it appears to in good condition, and display and buttons look good.It can measure mV ( havnt verified precision, but it measures), but V and A shows OL in the display ( after a short flicker)A quick look inside does not reveal anything burned.I assume that the "measuring core" is good because its can measure mV, - but maybe that's a flawed logic?I tried taking apart the function-selector-switch and all looks good.I cant find any schematics or service manuals.Any ideas? -it looks like a great meter, but I dont have the time to reverse-engineer something like that at the moment.Kind regards TroelsM

author: shakalnokturn
author_rank: Super Contributor
timestamp: February 22, 2024, 04:27:56 pm
content: I own a couple of these and could make comparative measurements (only) once you've spent some time deciding what interesting test points could be.I don't know if calibration constants are stored in external EEPROM or internal to CPU on this model, if no one else out here has made dumps available I may also go to that bother.You do not mention how it behaves for resistance and capacitor measurements.Have you started with the basic checks that can tell you quite a bit on what's going on:Link it up to another multimeter, measure input input resistance while cycling through voltage ranges and current ranges.In Ohmmeter measure output voltage and current on different ranges.Most handheld designs don't use the precision resistor network for the mV range so may be worth looking if that isn't broken.

author: TroelsM
author_rank: Newbie
timestamp: March 04, 2024, 05:39:17 pm
content: Thank you for the kind offer, but Ii wont asku you to go through all taht trouble for me.I tried measuring from inoput terminal to the precision resistor network, -assuming that there would some veldefined path from input terminal in Vdc mode.My readings did not make much sense to me, but maybe Ii was looking for a lowish-value, and in reality theres a very high impedance?Anywhos, not finding a clear path, I looked at the mode selector again. There is 2 decks of switches connected by a plastic part.The switches must align and alsoe align with the plastic part for mode-selection to be stable.Ii tried moving the plastic-part relative to the 2 switches and apparently that did make difference.i looks like everything but the AC-ranges work now. - that would indicate a broken AC-coupling cap, but thats the last component I would normally suspect. Therefore Ii assume that this is also related to the mode selector somehow?Ii have decided to leave it as-is for now. Ii have other meters for AC, and i will wait a little and see if the "fix" on he DC ranges is stable over time.Kind regards TroelsM
faulty insulationresistance meter. - Page 1
Forum section: electronics / repair

author: kakha4
author_rank: Newbie
timestamp: August 12, 2022, 12:44:26 am
content: have a faulty IR continuity tester (CABAC model T2732). On the 500 ohm setting(when doing initial testing) the needle deflects to 50 ohm only whereas it is meant to give a full scale deflection to 500 ohm whereas on the 3 ohm setting the needle give s a full scale deflection. any suggestions as to what could be causing this?.

author: themadhippy
author_rank: Super Contributor
timestamp: August 12, 2022, 01:27:31 am
content: Does the zero adjust do anything?

author: kakha4
author_rank: Newbie
timestamp: August 17, 2022, 01:25:34 am
content: its zeroed properly. tested on the 3 ohm scale. its just the 500 ohm setting when testing needle only deflects to 50 ohm range and not past it.confused??
Faulty Mackie HR624 Powered Speaker Amplifiyer Understanding Dim Bulb - Page 1
Forum section: electronics / repair

author: Timmox
author_rank: Contributor
timestamp: May 17, 2025, 01:15:03 pm
content: Hi All,In the process of learning amp repair/more advanced electronics and need some advice.I have a faulty Mackie HR624 powered monitor speaker on my bench. The symptoms are it instantly blows it's internal fuses. I'm trying to diagnose the fault use a dim bulb tester (for the first time). When connected to the DBT the bulb lights fully bright. I have removed the amp from the speaker and disconnected the output from the tordial transformer from the circuit board (see 1st attached picture, 3 brown wires going it to white connector) and I still get full brightness from the bulb. If I also disconnect the input to the tordial transformer (see 2nd attached picture, yellow sleeved wires with 4 wires to black plug) the bulb does not light.This makes me think the transformer is faulty, however as a novice I appreciate I could be reading the results wrong.Any help would be gratefully apricated.Cheers,TimP.S. I have tested the DBT on a functioning amp and is does not light.

author: Grandchuck
author_rank: Super Contributor
timestamp: May 17, 2025, 01:48:41 pm
content: It seems the transformer is shorted.

author: Timmox
author_rank: Contributor
timestamp: May 22, 2025, 12:58:55 pm
content: That was what I suspected. Many thanks.

author: suntime
author_rank: Contributor
timestamp: May 22, 2025, 07:23:48 pm
content: Hi,Note that there is a 120V - 240V switch, which places the two primary windings of the transformer in series or parallel.I would check that the two windings are not in parallel, which could explain the fuses blowing.Regards.Schematic:HR624_mkii.pdf
Faulty parts Dell Optiplex 780 SFF Power Supply - Page 1
Forum section: electronics / repair

author: tedge
author_rank: Newbie
timestamp: November 29, 2019, 09:53:27 pm
content: Faulty parts Dell Optiplex 780 SFF Power SupplyI have been looking for several weeks forcircuit diagram. Model H235P-00. P/N:HP-D2352A0 Power Supply 235W. I wonder if anyone knows where I can find a schematic.Many thanks to spilihps for the question. The link to the diagram in the forum is helpful but I cannot read the part values and number on the circuit board and would be very grateful for a diagram at higher resolution.These are the faulty chips so far found.(a) Fuse F 6.3A 250V 370(b) ST W7NK90Z CC OPC VW MAR825(c) 23NM60N GK03P V3 CHN 939My second 780 SFF Power Supply PSU(d) TNY280PN K818 54478A top of chip blown out.--------------------------------------Third780 SFF Power Supply PSU. Need circuit diagram forDell P/N: R224M P/N PS-5231-5DF1-LF 235Over a period of time failed post on a number of occasions.With Error codes looked like motherboard problems.Proved mother board was OK by using standard ATXPSU with a PWR adapter cable bought on Ebay for about £1.48 (Ebay item 143402320070).The Dell Optilplex 780 motherboard has smaller PSU connector.Parts ordered on Ebay 29/11/2019 (ebay item number in brackets) most items from ChinaOrdered 5pcs STW9NK90Z W9NK90Z N-CHANNEL 900V 1.1W 8A MOSFET TO-247 ( 172821066742 ) £4.33.The original ST W7NK90Z was too expensive5pcs F23NM60N TO-220F new( 123324260374 )TNY280PN TNY280 DIP7 Integrated Circuit from Power Integrations £2.40ATX PSU Standard 24Pin Female to Mini 24P Male Internal Power AdapterConverter Cable For DELL 780 980 760 960 PC £1.48 (Ebay item 143402320070)2x 5A Radial PCB Quick Fast Blow Circular Fuse( 283561064019 ) £2.25Regards Tony Edgelearnsax.co.uk/talk

author: KaneTW
author_rank: Frequent Contributor
timestamp: November 29, 2019, 10:01:45 pm
content: Is there any reason to repair it instead of replacing it? SFF PSUs are dime a dozen.

author: tedge
author_rank: Newbie
timestamp: November 29, 2019, 10:28:13 pm
content: I bought a second hand SFF PSU. But it was cheaper to buy a used Dell Optiplex 780 last one I bought cost £15. My family like the Small Footprint computers and work well with Windows7 Ultimate 64 four of the computers are using dual monitors. We don't like Windows 10 and old hardware the performance is abysmal. 1tb Disk 4gig of Ram. We like the ESATA socket at the back of the computer. Between us we have 8 Dell Optiplex 780s if they crash the system I can cloan a rebuild in 30 minutes with Cloanzilla from a memory stick without even having to remove the covers and use a small psu for the external Esata disk.I would like to repair the 3 faulty PSUs to keep as spares.I don't normally repair ATX PSUs they are so cheap and easy to buy. Its a different matter for the Dells SFF.Regards Tony
Faulty treadmill controller - Endex DCMD57 - Page 1
Forum section: electronics / repair

author: Kevin H
author_rank: Contributor
timestamp: May 14, 2019, 06:46:02 am
content: My son was using our Tunturi treadmill last night - he ran on it for an hour at 10 khm, which is the most work it has ever done. Afterwards he noticed a burning smell. I pulled the controller board from it today and the source of the smell is obvious - a (rather small) resistor is black and charred. See image.The board model number is DCMD57 and it's made by Endex Auto Tech. Unfortunately the resistor is unidentifiable due to the burning so I have been looking at photos of the same board on-line and this resistor doesn't appear on other boards which otherwise appear to be identical. I haven't been able to find a wiring diagram for this board and it appears to be a multilayer board so working out the circuit is going to be difficult. Companies who sell a replacement board offer a later version which is quite different.Does anyone have any suggestions as to how I approach repairing my board?

author: Kevin H
author_rank: Contributor
timestamp: May 15, 2019, 12:45:45 am
content: I found a picture of the exact same board - see attached. It appears to have suffered the same way and has been repaired, but the new component doesn't look like a resistor. Any ideas what it could be?

author: xavier60
author_rank: Super Contributor
timestamp: May 15, 2019, 03:57:02 am
content: The replacement part looks like a fuse. The original might have been a fusible resistor.There are more complications there compared to usual switch mode power supplies.Is the motor control done on the live side?

author: Kevin H
author_rank: Contributor
timestamp: May 17, 2019, 02:10:41 am
content: Thanks for your response xavier60 and apologies for the delay in responding.I'm sure it didn't help that the component was covered with glue.QuoteNot sure what you mean by that?The motor as a 180v DC drive.As the treadmill was apparently still working when it was turned off, I decided to put the board back in and try it again. The damaged component starts smoking immediately the machine is turned on.

author: xavier60
author_rank: Super Contributor
timestamp: May 17, 2019, 02:31:08 am
content: It looks like the motor connects on the live side of the power supply, not the isolated side?

author: xavier60
author_rank: Super Contributor
timestamp: May 17, 2019, 02:52:37 am
content: Also check to see if the overheating part is in the motor current path.

author: Kevin H
author_rank: Contributor
timestamp: May 17, 2019, 03:38:11 am
content: Quote from: xavier60 on May 17, 2019, 02:31:08 amI don't think it does, but I will check.QuoteAgain, I don't think that is the case. One side of the component is connected to the incoming AC neutral line.I have removed it now (see photo attached ) and it has a resistance of 35 ohms.Either later today or over the weekend I will dismount the circuit board and trace out the circuit so we have a better idea of what we are dealing with.
Faulty voltcraft vsp 2410 - Page 1
Forum section: electronics / repair

author: makito85
author_rank: Newbie
timestamp: May 07, 2025, 03:21:22 pm
content: Hello,I recently purchased a used Voltcraft VSP 2410, which has dual 10A 40V outputs. One of the outputs was broken, so I measured the components and waveforms on the working side for comparison. Unfortunately, during this process, the working side also failed.After inspecting the components, I found that the MOSFETs and two Zener diodes were faulty. I replaced them, but the MOSFETs kept failing repeatedly.One strange thing I noticed is that the datasheet I found for the VSP 2410 shows different MOSFETs than the ones that were installed. The installed MOSFETs were IRFP460, while the circuit diagram (which I have attached511142-sp-01-en-Labornetzgeraet_VSP2405HE-1.pdf(2340.93 kB - downloaded 16 times.)) specifies IRF840.I decided to try the IRF840, and with those, the power supply worked. However, when I use the IRFP460s that came with the device, neither output functions, and the MOSFETs are consistently destroyed.I'm puzzled as to why the IRFP460s worked initially but now fail, and I cannot use the IRF840s because they are not isolated.Any insights or suggestions would be greatly appreciated.Thank you!

author: MathWizard
author_rank: Super Contributor
timestamp: May 07, 2025, 11:10:24 pm
content: So is the Voltcraft a SMPS or linear PSU ?Just for reference, the 'Array 3711' electronic load, I'm pretty sure the 300W version, which is upto 360V or 10A, , uses 8x IRFP460.There's some differences for sure, but what matters the most, IDK.460https://www.vishay.com/docs/91237/91237.pdf840https://www.vishay.com/docs/91070/91070.pdfAny chance the parts were fakes ?
FeelElec FY6900 No output fix - Page 1
Forum section: electronics / repair

author: mags2021
author_rank: Newbie
timestamp: December 05, 2021, 07:59:22 am
content: Recently bought a FeelElec FY6900 arbitrary waveform generator. It worked fine for about 2 days then stopped outputting frequency from CH1 and CH2.Also would not connect to the PC software. I tried everything in the menu's to no avail. I opened the case and started looking around for anyvisual problems. Did not see any problems. I started tapping on several of the IC' and the output started to work but stopped again. I decided toreflow the solder joints on the main IC, since both outputs were bad and I didn't suspect individual channel issues. It is now working fine. Wanted to sharethis since there is limited info on these waveform generators.

author: ltarjanyi75
author_rank: Contributor
timestamp: March 19, 2023, 04:19:53 pm
content: Hi! I had similar issue today with my FY6900. It started to behave strange lately: not all frequency and voltage settings where changing the output. Than today it did not output any waveform at all on either CH1 or CH2. Opened its box to investigate but it started to work when I switched on. Tried to find any loose soldering by nudging the components but did not show any problem. Put together and works fine now. Strange...
FeelElec FY6900 Strange chopped default Sine wave - Page 1
Forum section: electronics / repair

author: Phill Betts
author_rank: Newbie
timestamp: January 13, 2022, 04:42:52 am
content: A couple of weeks ago, I think after a power spike (I live in the country and they happen often) my FY6900 wave generator started producing a chopped sine wave as it's default sine wave.Any suggestions?Maybe a factory reset option?

author: rachsamazon
author_rank: Newbie
timestamp: October 05, 2023, 10:13:21 am
content: Hello sir !I have the same problem with chopped sine wave on my FY6900 have you fixed it maybe ?Thanks!

author: Audiofanman
author_rank: Contributor
timestamp: September 06, 2025, 03:01:59 pm
content: Shux.. my FY6900 just started this behavior.. Tried the options, sys and reset but no joy. Tried rebooting no luck... has anyone figured this problem out?
Feeltech FY3200s Repair - Page 1
Forum section: electronics / repair

author: Unordung
author_rank: Contributor
timestamp: February 07, 2020, 11:05:24 am
content: Hey guys,Quite a while back I kinda maybe sorta connected my cheap Chinese fun gen (Feeltech FY3200s) directly to 30V DC.Needless to say the fun gen was not impressed. Quite surprisingly the only damage was to the Chanel in question.It still generates the desired frequency and signal but the amplitude is at best 10mV.Thus I suspect the output amplifier for the channel 1 is damaged. Does anyone have a schematic for this unit before I go digging about?I have been Googling for about an hour and cant find one so you guys are my last hope.Regards

author: goaty
author_rank: Regular Contributor
timestamp: February 07, 2020, 11:53:33 am
content: https://www.insidegadgets.com/2015/02/20/inside-the-feeltech-12mhz-dds-function-generator/here probably replace LMH6643

author: Unordung
author_rank: Contributor
timestamp: February 07, 2020, 11:58:26 am
content: Not quite the same unit I'm afraid.That unit is USB input while mine is mains input.The PCB is entirely different.

author: goaty
author_rank: Regular Contributor
timestamp: February 07, 2020, 11:04:58 pm
content: Ah ok, didn´t read its another model...Here´s a picture of yourshttps://chinese-electronics-products-tested.blogspot.com/p/fy3200s-function-generator-tested.htmlGuess it´s the chip under the heatsink then. Maby you can replace it.

author: Giorgio Santantonio
author_rank: Newbie
timestamp: October 19, 2023, 04:11:03 am
content: Did you fix the problem? I have the same identical issue and I'd be interested to have an help in fixing the problem.Thank you
Fender 400PS bias issues - Page 1
Forum section: electronics / repair

author: average joe strummer
author_rank: Newbie
timestamp: October 16, 2019, 11:09:12 pm
content: Hello allNew member here. I have been repairing tube amps for some time and understand the dangers and safety issues involved with working with high B+ voltages.My question here is how to bias the 400PS correctly. I have been following the Ed Jahns 30 point setuphttp://www.timeelect.com/400-upmod.htmI can get the -39VDC on the bias pots and all components were verified to be installed correctly. I have a measured resistance across OT at 6.2 ohms and 5.5 per side. 692 & 695VDC per side plate voltage, but voltage drop of 0.519 & 0.304VDC per side seems to be drastically different. This is giving me 53.6 & 35.2 watts plate dissipation which I think is scary high for 6550's. I have installed new electro caps throughout the amp, all to spec, and new caps & resistors on power tube sockets.What is the ideal plate dissipation for this amp, how can I balance the voltage drop of the OT, and does a radically different PD effect the performance? Schematic is in the link above.https://www.jj-electronic.com/en/6550Thanks to any knowledgeable minds who can point me in the right direction.CheersAJS

author: floobydust
author_rank: Super Contributor
timestamp: October 17, 2019, 12:23:01 pm
content: An amp like this does need individual bias trimpots unless you are a rich man.The 6550's are "special design" selected Tung-sol's and matched as an entire set. Pushing them pretty hard with a plate voltage of 700VDC."bias set for total ~210mA", is about 35mA each for 24.5W quiescent. With cathode resistor 10R, for 0.35V each. You're getting from 30.4mA to 51.9ma?Those tubes aren't matched that great, well enough to work here or there are damaged screen/plate resistors. The OT asymmetry is not the problem, it's not going to make the Q-point that far out.You have to at least get each side (set of three on OT leg) closely matched so you can work with the balance pot.I would set the bias equal and measure then sort the tubes by cathode current, then shuffle them in each side so that is best matched, then do the bias balance to bring the entire set close together. Otherwise, you will just bake the tubes having higher transconductance and it will be in the shop again.Having mismatched tubes between each side does affect distortion, but Fender does not allow any other way to set bias.

author: Renate
author_rank: Super Contributor
timestamp: October 17, 2019, 06:57:41 pm
content: Yup, floobydust has all the numbers that I wanted to say.It wouldn't hurt to check the 10 ohm resistors just in case.How many speakers are you using? Will you use?If it's only one, you're only using a pair of tubes.You can easily adjust the bias dead-on for that.(The other four tubes can be stored away for later.)

author: average joe strummer
author_rank: Newbie
timestamp: December 16, 2019, 10:44:50 pm
content: Sorry guys, haven't logged in for a while.Got it sorted nicely. Appreciate the help.

author: floobydust
author_rank: Super Contributor
timestamp: December 17, 2019, 03:22:01 am
content: What was it?