hybridfree/eevblog-posts huggingface dataset:
Debugging multiplexing AD converter ADC0809 - Page 1
Forum section: electronics / repair

author: eric appla
author_rank: Newbie
timestamp: September 12, 2020, 04:04:34 pm
content: Hello fellow technicians.I have an old instrument based around two Z80 processors which is using 4 60mm slider pots to list through menus. I have a problem that in some menus slider won't change anything for say first 20% of the travel then it would list through all the values and towards the last 20% it would do nothing again. When you have say 100 items in the menu it's quite annoying that only small area of the slider is being utilised.4 sliders are linear 10k pots connected as a voltage divider. The AD converter is ADC0809 and Vref + is 5V and equal to Vcc and equal to the slider voltage before division. Vref - is tied to GND and again there are no noticeable variances in the GND potential. It's all within 10mV which is less then 1/2 LSB resolution regardless.I have confirmed the input voltage to the ADC scales linearly and correctly and the references are OK and there is no significant ripple to cause this issue.I have tested 3 different ADC0809 chips to ensure there isn't a hardware fault.I would like to use Logic Analyser to confirm the ADC is doing it's job and that on fact the fault is in the software implementation.If I connect all 8 bit wires to the LA and the 3 address wires I should be able to start the capture and move the slider in either of the "dead zones" and observe if I can see the value change. I wonder if there is a better way I could in situation test the AD linearity?Any ideas are highly appreciated
Debugging PC motherboard that won't power on - Page 1
Forum section: electronics / repair

author: dorkshoei
author_rank: Frequent Contributor
timestamp: May 10, 2022, 03:52:48 pm
content: Are there any good tutorials that focus on debugging PC motherboards that won't power on?If I jumper the PSU-ON all PSU voltages are good (obviously no load). I have 3V power to the on/off switch pins on the motherboard. I've cleared NVRAM, reseated RAM, tested the RAM in another machine, reseated the CPU but it won't power on.

author: PKTKS
author_rank: Super Contributor
timestamp: May 10, 2022, 04:06:21 pm
content: short answer = NOno tutorial will really help... although dozen of "courses" will put a mosaic of knowledge in front of you.Long answer = not even with these mosaic of tips you have a direct path...Reason being .. the MOBOs changed too much ...You need the bare bones of each "class"For example a couple common reasons of failing boot:- Bad or corrupted BIOS and/or firmware- Firmware today lies into "parts" - even the Super I/O on some mobos on some models has firmware- Bad power rails - the advent of iGPU made the PDU (power distribution) on mobos change a lot- from simple sparse regulators to complex multiphase VRMs .. you just need to check themBEFOREpowering a bad mobo..- Corrosion - and that comes with air flow.. and that can ONLY really be spotted with microscopes and some practice..bottom line you will need also- some minimum schema of the mobo - VRMs can be complex- o GOOD BIOS POST CARD.. although these UEFI based boards can mess up a lot..- some good de soldering tools..no jump start reallyPaul
Decent contact re-plating pen? - Page 1
Forum section: electronics / repair

author: Rat_Patrol
author_rank: Frequent Contributor
timestamp: April 23, 2023, 04:13:50 am
content: Son is into retro video games, has a few old Nintendo cartridges that need the connectors re-plated. Looks like they were copper plated originally according to his research, so not sure if that is the best route to go with, or maybe go with gold plating? IIRC, you need nickel between copper and gold, correct?Anyway, any good US sources for a not-crap-grade plating pen? We have a few DC power supply sources he can use, so just need the pen and a lead on solution if you have it.
decent uk sourced contact /switch cleaner spray - Page 1
Forum section: electronics / repair

author: m3vuv
author_rank: Super Contributor
timestamp: January 02, 2022, 11:30:44 pm
content: Can anyone recomend a good contact cleaner from the uk thats dot a total rip off ie deoxit.

author: artag
author_rank: Super Contributor
timestamp: January 02, 2022, 11:50:28 pm
content: Electrolube contact grease is decent.Their spray is pretty generic : it certainly doesn't have the supposed features of deoxit.I don't know whether deoxit lives up to its claims - I did buy a selection pack a while ago but haven't had a target to test it on yet. I don't generally rate sprays very highly though.

author: Audiorepair
author_rank: Frequent Contributor
timestamp: January 02, 2022, 11:55:15 pm
content: https://uk.farnell.com/kontakt-chemie/kontakt-60-100ml/cleaner-kontakt-60-100ml/dp/800909
Deciphering the worst manual ever: Ortec VT120 repair - Page 1
Forum section: electronics / repair

author: ChristofferB
author_rank: Frequent Contributor
timestamp: April 09, 2021, 09:15:15 pm
content: Hi! I've recently bought two Ortec VT120 "fast preamp" for channeltron timing experiments. I can't get them to work..This is not necessarily the amplifier's fault, since they're 10-350 MHz bandwidth, and I don't think I have anything that produces rising edges that steep.Either way, there's only 3 transistors in them, and no other semiconductor components, so I thought swapping them would be an easy attempt at a fix. The two shows the same characteristics with a slow pulse input: an output about half as big as the input; they're supposed to be 20x volatge gain.now, the manual from Ortec:https://www.ortec-online.com/products/electronics/preamplifiers/vt120is fine, but the resolution of the schematics.. jeez.Can anyone tell the model numbers on the transistors?? I'm at a loss. See below.Thanks in advance!

author: ChristofferB
author_rank: Frequent Contributor
timestamp: April 09, 2021, 09:24:06 pm
content: Oh, and the input clamping diode package as well!I think those might be bad. Could they be swapped for something like normal back to back 1n4148's?They're BAV99's.

author: ChristofferB
author_rank: Frequent Contributor
timestamp: April 09, 2021, 09:33:57 pm
content: Here's a picture of the board, the right is input, left is output. I havent gotten much luck with the smd part numbers.

author: xrunner
author_rank: Super Contributor
timestamp: April 09, 2021, 11:33:27 pm
content: Well, I played with a bunch of transforms and maybe it's clearer. Best I could do is attached.Does it look like the transistors begin with BF? I can make out some numbers. Maybe if you use that you can find something. I played with Irfanview to get that much.

author: ChristofferB
author_rank: Frequent Contributor
timestamp: April 10, 2021, 12:58:59 am
content: Thanks for your effort! Yes, BD or BF.. the rightmost one looks like it sais BD912, which does exist but is a TO220 power BJT.

author: Messtechniker
author_rank: Frequent Contributor
timestamp: April 10, 2021, 05:13:28 am
content: BF is most likely. BF transistors are commonly used in high frequency applications like this one.A BF 812 does exist. Maybe 8 is being misread as 9.

author: picburner
author_rank: Frequent Contributor
timestamp: April 10, 2021, 06:13:52 am
content: Judging by the application and the SMD code they could be:BFR93BFR93BSR12I would definitely not replace the BAV99 with two 1N4148.
Deckel CNC2102/2101 eprom dump need - Page 1
Forum section: electronics / repair

author: satanistik
author_rank: Contributor
timestamp: August 20, 2022, 07:26:58 am
content: I need eprom-s dump for this vintage cnc machine controler.I have problem width NMP51 module - on CRT i have only 00 and no responce to anythink. Botom board (plc) work - i can switch some outputs from botom keyboard. Eproms have 40ys and retention time is ending, if someone have this parts its last chance to backup.
Decoding component properties on a schematic - Page 1
Forum section: electronics / repair

author: bson
author_rank: Unknown
timestamp: August 15, 2025, 05:31:53 am
content: I have a schematic with various component properties I'm not familiar with. This from a JVC XL-Z1050TN CD player (early 90s design).Some capacitors have values like:C3410.068, GnHI take this to mean 0.068uF.Most of these are oblong drop-shaped axial polypropylene caps.Any idea what nH might be? My best guess is non-healing? Or is it just code for PP?I notice that caps are sometimes either J or G, while resistors are sometimes F. Perhaps F is metal film and J, G are types of PP caps.Some caps have an explicit voltage so that doesn't seem to be related.I've never seen this before...

author: bson
author_rank: Unknown
timestamp: August 15, 2025, 05:57:15 am
content: Actually, looking through the parts list (this service manual is awesome)... it seems like polypropylene caps have either J or G. So it's not a type code. Tolerance perhaps?

author: Simmed
author_rank: Frequent Contributor
timestamp: August 15, 2025, 06:50:31 am
content: from interwebsF 1%G 2%J 5%H should be 50vbut what is "n"https://www.electronics-notes.com/articles/electronic_components/capacitors/capacitor-codes-markings.php

author: Kean
author_rank: Unknown
timestamp: August 15, 2025, 06:52:55 am
content: Quote from: Simmed on August 15, 2025, 06:50:31 amMaybe non-polarized?

author: bson
author_rank: Unknown
timestamp: August 15, 2025, 06:14:50 pm
content: Quote from: Simmed on August 15, 2025, 06:50:31 amNice!!! Thank you!

author: inse
author_rank: Super Contributor
timestamp: August 15, 2025, 07:58:47 pm
content: I second n=non polarized, all capacitors except the one electrolytic on the very left have the n marking

author: bson
author_rank: Unknown
timestamp: August 15, 2025, 10:33:16 pm
content: That might be correct... but what does H stand for?

author: TimFox
author_rank: Super Contributor
timestamp: August 15, 2025, 10:39:23 pm
content: As stated above, perhaps "50 V", a reasonable voltage rating for a small film capacitor.Again, as stated above, "F" = 1%, "J" = 5%, and "K = 10%" are very popular codes for component value tolerance.They are part of a larger sequence that includes the less-popular tolerances B = 0.1%, C = 0.25%, D = 0.5%, G = 2%, and M = 20%.I don't believe there is a tolerance code "H".

author: bson
author_rank: Unknown
timestamp: August 15, 2025, 10:48:23 pm
content: Although I see C343, which is Mylar (and so non-polarized) doesn't have the "nH" marking. It seems unique to PP.

author: bson
author_rank: Unknown
timestamp: August 15, 2025, 10:50:13 pm
content: Quote from: TimFox on August 15, 2025, 10:39:23 pmThe PPs are, it seems (I didn't check the whole list), 100V...But yeah, the one-letter codes seem to be tolerance, which makes perfect sense.
DECT baby monitor - Page 1
Forum section: electronics / repair

author: slacker878
author_rank: Newbie
timestamp: December 25, 2021, 06:31:11 am
content: I have a baby monitor that is acting up.the receiving unit appears to be very soft in volume.I do not know if its a sender unit problem or a receiver unit issue.I suspect its a sender unit issue - specifically the microphone, so i bought another cheap electret microphone to replace it - volume is much louder but it resulted in constant static as well.now i am at a loss and do not know what to do else to test/troubleshoot. is it just the wrong microphone i bought?original microphone has a DC resistance of 1.26kOhm. no symbols or numbering to indicate maker or model.open voltage on the end of the wires to the microphone is 2.8vmicrophone connects to TP99 (+) & TP100 (-) on the bottom of the circuit.is it a microphone issue or another common component that can be easily replaced?I do not have a signal generator , just a basic multi-meter.thanks.A

author: rpiloverbd
author_rank: Regular Contributor
timestamp: December 25, 2021, 01:44:16 pm
content: Hello,Actually, it's hard to tell if you don't have the circuit diagram. But don't worry. As you have a multimeter, kindly do a continuity test to figure out what components are connected to the microphone. I think that will give you a lot of answers.

author: slacker878
author_rank: Newbie
timestamp: December 25, 2021, 11:50:14 pm
content: the only few things that are connected are a few resistors and a single cap (I think) - Z203 bottom right.can identify the rating though, its a 07 :5 written on it. using my multimeter it reads 51 microF - make sense? i cant get a chart anywhere on the net.the cap beside it is also labelled the same but not connected to the microphone based on continuity - can't get a reading on the multimeter though. make sense to any one?

author: SoundTech-LG
author_rank: Frequent Contributor
timestamp: December 26, 2021, 11:59:49 pm
content: The original microphone is likely an electret condenser mic, requiring bias voltage, and correct polarity to power it.Which is why you have DC voltage you measured.You did not tell us anything about what your replacement microphone is.

author: SoundTech-LG
author_rank: Frequent Contributor
timestamp: December 27, 2021, 12:21:54 am
content: Yes, replace items even if they are fine. Then, move on to actual troubleshooting.

author: slacker878
author_rank: Newbie
timestamp: December 27, 2021, 02:47:32 am
content: Quote from: SoundTech-LG on December 26, 2021, 11:59:49 pmreplacement microphone is also an electret mic 9.5mm. I did attach the correct polarity. it worked after replacing it but there was constant static as well.this is the supposed specs but I will take it with a pinch of salt:https://www.jaycar.com.au/medias/sys_master/images/images/9593315688478/AM4011-dataSheetMain.pdfQuote from: barycentric on December 27, 2021, 12:37:30 amactually my multimeter can test caps.the electrolytic capacitors are generally ok - most are reading within their specs. 100microF - reading as 226 microF, 300 microF reading as 220microF, 470microF reading as 540microF, 47microF reading as 52microF.
Deebot Ozmo 950 charging issue - Page 1
Forum section: electronics / repair

author: strobonautiker
author_rank: Newbie
timestamp: November 15, 2022, 10:02:04 am
content: Hi folks,I've got a faulty vacuum robot "Ozmo 950" here that refuses to charge the battery. I checked the charging station and the connections, I get all the voltages to the mainboard. I recharged the battery on a laboratory supply and it works fine.So I traced the fault to an area of the board I assume to be a switching supply for generating the charging voltage and I found a faulty diode that does not read any forward voltage in either way. I tried to exchange it with a random rectifier diode and I got a change, that means I can hear a buzzing sound now coming from the mainboard and the voltage on one side of a mosfet has changed from the full 20 V that come out of the charging station to roughly 0.3 V below the battery voltage, in this case 14,5 V. This means there is still no charging going on right now. I guess that the forward voltage of my random diode with its ~ 0,5 V might be too high for the circuit and I might need one with a lower Vf.Now my problem is that I don't know what spec the original diode has. I identified that manufacturer of this diode to be Good-Ark, but the marking just states KN BZ or maybe KN B2. I went through I think all the datasheets on their website but could not find any parts with this marking code. Do you have suggestions for a beefy Schottky diode with 0,2 V Vf?Possibly the Mosfet? could be faulty as well. It reads a diode one way over D-S but I cannot figure out its type from the marking. The manufacturer's logo is an A within an ellipse, so maybe also from Good-Ark but it differs from the diodes. The numbers read 31321 and EL9327.Do you have any tips on how to proceed or figure out the marking codes?This failure seems to be quite common with this model. I even found a comment on an Ecovacs video on replacing the battery, that after around 2 years the mainboard may need replacement. But a replacement mainboard costs 135 € and is not available right now.Cheers!
Default "melodies" for LightwaveRF LW-6007 Door Chime - Page 1
Forum section: electronics / repair

author: perdrix
author_rank: Frequent Contributor
timestamp: July 02, 2024, 04:11:54 pm
content: Does anyone have one of the subject door chimes? The previous owner of the one I inherited with this house had deleted all the original "melodies" and replaced them all with "We wish you a Merry Christmas" which is driving me nuts. LightwaveRf has discontinued itDoes anyone have one of these door chimes and if so could I ask you to connect to the USB port and pull the wav/mp3 files from it - they should be:1. Westminster2. Ding Dong3. Ding-Dong-Ding4. Tubular-15. Orchestra6. Tubular-27. Trumpet8. Dog barkingThanksDavid

author: Kim Christensen
author_rank: Super Contributor
timestamp: July 02, 2024, 04:27:33 pm
content: Why don't you just find the chime files you want from the internet?For example:https://soundbible.com/1466-Doorbell.htmlIgnore the "file can't be downloaded securely" BS, and click "keep"... Or find another site with free WAV and MP3 files.
Defect P-FET type - Page 1
Forum section: electronics / repair

author: Wimbledon013
author_rank: Newbie
timestamp: June 29, 2020, 08:50:20 pm
content: I have a The One light smart Piano to repair, it is broken because they put 42V instead of 12V on it.Now I have found the main broken component and it is what I think a P-FET is in the 12V power line.If I bridge the FET the Piano works.Now is my question what type P-FET is it, I have tried to search on the marking but can't find the component.

author: WattsThat
author_rank: Frequent Contributor
timestamp: June 29, 2020, 08:57:07 pm
content: Alpha & Omega AOD407.http://aosmd.com/res/data_sheets/AOD407.pdf

author: shakalnokturn
author_rank: Super Contributor
timestamp: June 30, 2020, 02:28:18 pm
content: Quote from: Wimbledon013 on June 29, 2020, 08:50:20 pmYet another victim of "Phantom power"?

author: m3vuv
author_rank: Super Contributor
timestamp: July 01, 2020, 01:04:13 pm
content: Was the fault caused by the not me fairy?
Defective smps. JBL Prx 612M - Page 1
Forum section: electronics / repair

author: blipblob
author_rank: Newbie
timestamp: March 24, 2025, 06:44:38 pm
content: Hello! I have two active Jbl speakers whose amps have both given up in the same manner and i cant wrap my head around as to why. The speakers were defective when i got ahold of them and the previus owner had no recollection of what led up to them failing.You can find the schematics here:https://drive.google.com/file/d/1RdyRLzuaYKMFrCIkkKhdjH_cK9qlyAJb/view?usp=drive_link(the schematic is for a three way model but the smps seems to be identical.)There is no Vcc, R 612 (D3) gets really hot and the gate drive circuitry had blown up. No fuses had blown though.Both amps had blown up q601 (C6). Once amp had blown up U603 (C6). One amp had shorted out the Igbts, q606 had all three pins shorted, q605 just drain and source.Ive tried replacing the tl494, U603, the gate drive transistors and the high side igbt. Originally there was a GB20B60Pd1, but i replaced it with the IKP20N60T.All seemed fine when i tested the circuit without the igbts connected but when i connected them the gate drive circuitry blew up once again almost immediately after turning the amp on. Both the new igbt and the old one shorted out. Im unsure if i checked if the old one was ok beforehand though.What follows now are just a couple observations:With the gate drive circuitry desoldered I get the 2.2khz signal from the tl494, But it stops for a split second about once a second since the supply voltage slowly drops. Once the 494 stops the voltage jumps back up again.The primary side isnt ground referenced and i dont have a differential probe so all my oscilloscope measurements have been done by subtracting channel B thats connected smps ref from channel A.When viewing 15v its shaped like a 50hz square wave, approx 50% pulse widh and jumping between ca 15v and 4v.The voltage at pad 8 where u603 would sit is constant at ca 140v as inherited by "1/2vbulk".Disconnecting F1 leaves the voltage at +-100v ac against ground or ca 140+-90v dc against smpsref. Disconnecting C627 gives 15v.Soldering U603 back in place and measuring gives a square wave at Lo. Ho jumps up to ca 55v and glides down to 15v at the same rate as 15vcontroll. Removing c627 doesnt change anything. I tested with another ic but got the same result, might just have burnt both ics.If you have ANY ideas as to what might be wrong with my amps id love to hear em! if you have further questions or need clarification ill make sure to respond asap!
Definitive Technology SC2000 Thump when powering on - Page 1
Forum section: electronics / repair

author: rosshenning
author_rank: Newbie
timestamp: December 15, 2024, 09:41:20 pm
content: Hello,I have a Definitive Technology Supercube SC2000 which has worked flawlessly since 2015 when I purchased it. Recently, it started having a hard time powering on. By that I mean that it has no power switch, but has a circuit that monitors that line in and when a signal is present, the subwoofer is turned on. Recently, it began clicking on, then clicking an extra 2 or 3 times before it would lock in with around 1 second between clicks. Over a few weeks time this grew from 2 - 3 clicks to more like a dozen. At this point I knew I needed to do something. My first assumption was that the electrolytics had dried out. I've gone through and replaced all non-SMD electrolytics (The low level PCBA section is all SMD, all the other boards are through hole components), and did find that almost all of them were way off of their printed values. The sub no longer has a hard time starting up. One click and it's on. However, the problem I have now is that it comes on with a "Thump" where it used to start up silently. I've checked for DC offset at the speaker, and it's right around 1mv.I've looked over the schematics (attached), but have very little experience troubleshooting to this level. I'm hoping that you guys might be able to give me suggestions as to what I should check. I don't have any experience with SMD components, and I have none in-stock, however, after watching some Youtube videos on it, I feel comfortable replacing the SMD caps if necessary. I would just need to order them. Looking at the schematics, those don't look like likely culprits to me, but I realize I could be completely wrong.Thanks in advance for your assistance!

author: fenugrec
author_rank: Frequent Contributor
timestamp: December 17, 2024, 01:22:11 am
content: That is not a simple amp, but you could start with p.7 of the HD800 pdf you posted. Look at "driver_enable", amp_enable, mute signals at power-on, with an oscilloscope. There is a note that says "1s delay to ON, 0ms delay to OFF", and I would definitely start there. I would probably probe the output as a trigger while inspecting that area and the power rails.In a perfect world you would find + borrow locally a similar model and compare measurements, but you may get lucky and find an obvious cause.
DEI GPR-20 manual needed, - Page 1
Forum section: electronics / repair

author: CaptDon
author_rank: Super Contributor
timestamp: December 12, 2020, 11:13:01 pm
content: Greetings, I bought a Defense Electronics Inc. General Purpose Radiomodel GPR-20 from an Ebay seller. A couple of minor repairs and itseems to mostly work. The peak center response of the spectral displayoutput seems way out of whack with the rest of the radio and the C.W.function seems to be amiss. The signal meter pins on the high side andno recovered signal. I would mainly be looking for a manual with schematicor even just a readable schematic. This thing may be dinosaur technologyas it seems to work from negative 16vdc which usually indicated mostlyall PNP transistors. Thanks for any help/leads!! I will probably cross postthis in the Ham Radio forum also.
Delayed Start of the Motor in Electric Trimmer - Page 1
Forum section: electronics / repair

author: Boris_yo
author_rank: Frequent Contributor
timestamp: July 03, 2023, 12:58:04 pm
content: Hello. The issue is this hair trimmer. It used to start with one second delay until it got to over 10 seconds. Yes I have been spraying electric contacts cleaner or rubbing contacts with IPA 99%but soon the issue would return. Here's a link to the video:https://streamable.com/m4i9n4I wonder what causes it. The battery installed is a single lithium AA at the moment. It happened with alkaline too. But once it starts and I turn it off again and then on it then works with no delay.

author: Kim Christensen
author_rank: Super Contributor
timestamp: July 03, 2023, 06:21:07 pm
content: Usually with these kinds of things it's a gummed up mechanical problem. Does it start if you tap it on the counter?Might just need some cleaning and lube on the cutting blades and motor shaft.

author: Boris_yo
author_rank: Frequent Contributor
timestamp: July 04, 2023, 02:37:33 pm
content: Quote from: Kim Christensen on July 03, 2023, 06:21:07 pmActually it does but not always. I tried spinning battery in place and whenever I reached certain directions the motor would either start but work not at its full power or start and work at its full power. I would then spin slowly again and it would either stop or slow down from full power. There is no gap between contacts so I wonder why.

author: Kim Christensen
author_rank: Super Contributor
timestamp: July 04, 2023, 03:07:59 pm
content: Lightly buff the contacts with a fine abrasive such emery cloth or brillo pad. There might be a bit of oxide/contamination on the contacts. This can happen to the battery too.

author: Boris_yo
author_rank: Frequent Contributor
timestamp: July 04, 2023, 03:55:10 pm
content: Quote from: Kim Christensen on July 04, 2023, 03:07:59 pmWill this happen again after I buff the contacts? The device is stored in bathroom's cabinet but compartment has the O-ring and is tightly closed.

author: Kim Christensen
author_rank: Super Contributor
timestamp: July 04, 2023, 06:19:41 pm
content: Yea, you'll probably have to do it again eventually. Just don't over do the buffing as most contacts have a thin layer over the base metal that you don't want to wear away. Just buff until they are shiny and then stop.
Delcon System 9x  - Page 1
Forum section: electronics / repair

author: ResR
author_rank: Regular Contributor
timestamp: October 02, 2019, 10:51:04 pm
content: The computer named Delcon System 9x from 1994 (it's very old-school, lots of logic chips) in an industrial concrete mixer station is showing 080 or 80 on weight displays, disconnecting the weight sensor controller doesn't affect, before the discovery of the fault the station wasn't been used in a while. Does anyone knows anything about this kind of equipment and how to fix it?

author: ResR
author_rank: Regular Contributor
timestamp: October 04, 2019, 07:04:10 am
content: Other shift found a problem with the computer itself, there was burned resistors and possibly multiple chips also, although clock generator and some of the circuit worked. It was decided to replace it with process controllers.
Dell 17 5770 keyboard problems - thoughts? - Page 1
Forum section: electronics / repair

author: alank2
author_rank: Super Contributor
timestamp: December 23, 2021, 01:11:57 am
content: Certain key combinations won't work. It might work with the right ctrl key, but not the left. Characters in the upper left corner are sensitive. Sometimes they work better, sometimes worse. You have to push them hard to get them to go, often giving two presses. I took the back cover off and unplugged the FFC and tried to apply some deoxit to it to see if a better connection there would help, but it wasn't any different. I was surprised to see so many pins, but it is a backlit keyboard although I don't think the backlighting is per key or anything. Is anyone familiar with the failure conditions of these? Apparently to replace it I would first have to find one which doesn't seem to easy, and essentially every part including the system board has to be pulled to change it. Could it be an issue at the FFC connector possibly? I think that may be wishful thinking, but I wondered if anyone else has run into Dell keyboard issues.

author: abdulbadii
author_rank: Frequent Contributor
timestamp: December 23, 2021, 03:59:58 am
content: Mechanical parts fault nothing with FFC, usually due to dust/dirt, age or tiny caps?

author: alank2
author_rank: Super Contributor
timestamp: December 23, 2021, 08:22:42 pm
content: It has the flat style caps. Does anyone know if the keyboard has an actual keyboard controller in it, or if it is just a matrix and the keyboard controller is on the motherboard?

author: wraper
author_rank: Unknown
timestamp: December 23, 2021, 08:24:56 pm
content: Laptop keyboards normally don't have any electronics in them.

author: flolic
author_rank: Frequent Contributor
timestamp: December 23, 2021, 08:28:54 pm
content: It's just a matrix. And there is no way to fix it, you can only replace the keyboard if something is wrong with it.

author: alank2
author_rank: Super Contributor
timestamp: December 23, 2021, 08:31:48 pm
content: Thanks; I appreciate it.

author: abdulbadii
author_rank: Frequent Contributor
timestamp: December 25, 2021, 01:17:38 am
content: Chicklet keyboardsits dubbed name, has taken over mechanical ones as the price is 1/7 lower of itmost if not all has its MC moved onto M/B
dell 2209wa monitor - Page 1
Forum section: electronics / repair

author: m3vuv
author_rank: Super Contributor
timestamp: April 19, 2021, 01:01:47 pm
content: hi all,ive just brought this non working monitor,all that happens on power on is the standby light in the power button flashes amber briefly once about every 5 seconds,checked various voltages on the main board,they rise and fall in sync with the power button led,all fusible resistors look ok,any ideas,will try and attach the service manual if it lets me,cheers in advance,ps,all the caps check ok for esr.the service manual is too big so heres a link:https://www.manualslib.com/manual/794321/Dell-2209wa.html

author: madires
author_rank: Super Contributor
timestamp: April 19, 2021, 01:30:21 pm
content: Shorted diode at the secondary side? Shorted load? Feedback problem? Issue with the power supply of the switching controller?

author: m3vuv
author_rank: Super Contributor
timestamp: April 20, 2021, 09:05:23 am
content: sorted it,it was a shorted schotty rectifier diode,replaced it with one from an old smps,works fine now,brought the monitor from ebay as spares or repair,not bad for £19 and a couple of hours work.

author: m3vuv
author_rank: Super Contributor
timestamp: April 20, 2021, 03:32:02 pm
content: wll it lasted about half hour then went off,found the diode was shorted again,the original was a mbr5200ive took a rf1601 tied the outer legs together mounted it on a heatsink,its been running for about 1hr and seems fine now.,its basicaly 2 diodes in paralell with a vf of 300mv.
Dell 5770 fan issue - Page 1
Forum section: electronics / repair

author: alank2
author_rank: Super Contributor
timestamp: June 01, 2024, 10:02:08 pm
content: I'd like to try to fix this notebook if I can. I thought it had a dead CPU fan because it does not run. Even when I go into the BIOS and sit. I have a second one of these for work and it runs the fan pretty fast/high when in the BIOS. So I ordered a new fan from eBay and it came today. Plug it in and it does the same thing. I connected up the original fan to my bench supply at 5V and it runs, so the original fan does work and both fans exhibit the same behavior. Now I'm thinking there is something wrong about the way it is being driven. It is a 4 pin port with black (ground), red (5V), yellow, and blue. I *think* yellow is the tach and blue is the control based on some Internet searching. I found if I connected up only the black/red that the fan would run so through trial and error I disabled the yellow (no run), the blue (runs), put back the yellow (still runs). It seems that with the control/pwm blue wire connected, it does not run, or I think I saw it run once really slow when it was int he BIOS and it should have been running full speed probably. Just to get my system up and running I pulled the blue wire out of the wire harness and am running it on the black/red/yellow, but as expected, the fan runs pretty much full speed all the time, when the CPU needs more cooling and when it doesn't.Any tips on what to look at next? I've already carefully resoldered the 4 smd pins for the connector on the PCB to make sure they are all a decent connection. That didn't change anything. Should I try to get a scope on the blue wire and see if there is any kind of signal? I'm not sure the trace for it is visible on the pcb.Also, as a second question, I loaded a program called core temp on both Dell 5770's. My work one seems to really shoot up on the CPU temperatures, not only do they jump around quite a bit, but it thinks nothing of jumping into the 90's deg C. It says Tj Max 100 C, but Im surprised it jumps around to much.

author: m k
author_rank: Super Contributor
timestamp: June 05, 2024, 04:01:01 pm
content: 1 and 4 are GND and control.2 and 3 are +V and sense.Control is to fan and sense is from it.Maybe there is a setting for 3-pin fan.CPU may have a bad heatsink contact.

author: alank2
author_rank: Super Contributor
timestamp: June 05, 2024, 06:09:39 pm
content: Thanks for replying. I ended up reconnecting the PWM wire and it started working. Not sure why, but I'm going with it until it stops.
DELL B2360DN firmware update corruption issue - Page 1
Forum section: electronics / repair

author: nouvelle_adr
author_rank: Contributor
timestamp: December 17, 2019, 07:59:35 pm
content: Hello,In desperation, I toss a bottle into the sea to try to get some helpPlease help, my printer seems to be failling back to ICP (In-Circuit Programming mode) during a faulty firmware update.I have an issue with my DELL B2360DN printer when I have tried to update the firmware (DELL .fls file). the upload has faced a corruption, and now it dont want to start (black LCD HMI)This printer motherboard has a Marvell 88PA6170 SOC, and now when I plug the USB cable to my computer to updload the firmware again, the DELL update tool shows the printer as "Marvellprinter" and not as a DELL (he sees a nude SOC), and the upload goes to 100% with success message, but nothing happen in the printer, it wont start.Did somone have a full firmware image ?or can extract NVRAM dump from his DELL B2360DN ?Or can give me a hint to solve that ?for information, here is the link I used to get the firmware that has corrupted my printer:https://www.dell.com/support/home/fr/fr/frbsdt1/drivers/driversdetails?driverid=47mn0&oscode=wt64a&productcode=dell-b2360dnThank you
Dell D825HT Vertical Problems - Page 1
Forum section: electronics / repair

author: juneberry
author_rank: Newbie
timestamp: March 28, 2020, 09:46:13 am
content: Hello all, a bit new here so I apologize if this may belong in the newbie section instead, I'm not 100% sure of where exactly my skill level falls based on the community's standards.Anyhow, a little over a year ago I acquired a pair of identical Dell D825HT monitors leftover from my university's math department cleaning their old equipment. One of them functions wonderfully save for being a tad dim and a bit off in the contrast area:On the other one however I ran into some strange vertical circuit issues. As seen here, the image is not completely drawn before the beam returns to the top of the screen:I did a little poking around with it in the past, but no extensive repair attempts. Now that we're all stuck inside thanks to the current epidemic I finally decided to completely commit to trying to repair it. After replacing all the capacitors on the mainboard (skipped the neckboard for now as parts on the mainboard are probably more important in diagnosing a problem like this, plus I didn't feel like desoldering the shielding and all to get to its parts), the image is complete when the beam returns to the top of the screen, but it still will not draw in the bottom 1/4 of the display, and the vertical adjustment controls on the front do not affect the image anymore:Since I have two identical monitors, I can easily swap components between them as necessary for testing purposes, and have indeed swapped the tubes to make sure nothing is inconsistent with the behavior of the yoke, etc. In addition, while Dell has not provided a service manual for this display, I did find that its internals are near identical to one of Sony's own CPD-100ES monitor, whose service manualcan be found here. Any guidance on where to go from here would be appreciated. The only other concern in my situation is that I may be a bit short on test equipment to fully diagnose what's going on, so only my trusty old RadioShack DMM has become my faithful companion through this whole thing.
Dell E2213H monitor fails to sync at power up - Page 1
Forum section: electronics / repair

author: timg11
author_rank: Contributor
timestamp: December 31, 2022, 10:41:02 pm
content: This Dell E2213H monitor has started to fail to sync at power up. This abnormal behavior is now consistent - it happens every time the monitor powers up, changes video modes, or the computer comes out of sleep, etc.I haveuploaded a videoshowing a case where it is out of sync for a short time, then syncs.Other times, it never syncs, and the scrambled image just freezes. I have to power cycle and it will try again.I've adjusted video timing (to the limited extent possible with HDMI monitors and the NVIDIA control panel), and it hasn't helped.Does anyone recognize this failure, or know the root cause of this issue, or have any information that could help me decide if it be worth trying to repair?
Dell E7450 LA -A961P - diagnostics after flooding and damaged PD817, PD5 diodes - Page 1
Forum section: electronics / repair

author: bpjl
author_rank: Contributor
timestamp: January 27, 2025, 09:03:34 pm
content: Hi,I have La-A961P Rev: 1.0 (A00) from a flooded laptop on the table. The computer was flooded with tea and at the same time the power supply was disconnected, the battery was removed immediately and the laptop was turned upside down.I looked at the mainboard, but I don't see any marks of water damage. Maybe the liquid did not reach MB, or maybe I just don't see it.During the inspection, I noticed a burned (charred on one side) double diode PD817.Voltage drops during PD817 measurements:- PIN1-PIN3 forward biased = 0.137V- PIN1-PIN3 reverse biased = 0.137V- PIN2-PIN3 forward biased = 0.445V- PIN2-PIN3 reverse biased = OLAfter removing PD817, the resistance between the fields where it was soldered, increased to over 20MΩ. Same between PIN 1 and GND and 2 and GND. Between 3 and GND is about 100kΩ.I also measured the resistance on the power socket and was only 5Ω. The reason was the PD5 diode.After its removal, the resistance on the power socket increased to 115kΩ.Another resistance measurements against GND:- +dc_in_ss = over 20MΩ- +3.3v_alw = 11kΩ- +5v_alw = 25kΩ- coil from VC_Core = 70Ω- all other coils = the resistance goes in kΩ- 8 leg of SPI = 117kΩSince the PD5 was damaged, I also made PQ2 and PQ3 measurements:PQ2:- D-S -resistance:over 130kΩ in both directions,voltage drop:+ on S = 0,559V, - on S = OL- D-G -resistance:over 140kΩ in both directions,voltage drop:OL in both directions- S-G -resistance:47kΩ in both directions,voltage drop:OL in both directionsPQ3:- C-B -resistance:over 47kΩ in both directions,voltage drop:+ on C = 0,643V, - on C = OL- C-E -resistance:over 35kΩ in both directions,voltage drop:+ on C = OL, - on C = 1,922V- B-E -resistance:14,9kΩ in both directions,voltage drop:+ on B = 0,67V, - on B = OLWhat else should I check before trying to power on this mainboard?

author: benj38
author_rank: Frequent Contributor
timestamp: January 27, 2025, 09:46:41 pm
content: If all the PCBs are free of water and corrosion, there is no reason you should not power the thing up and just see what is going on. If the unit still does not work, it would be much easier to repair when you can make voltage and signal measurements.The probability that when you apply power more things will fail is very small if there is no more liquid anywhere.

author: bpjl
author_rank: Contributor
timestamp: January 28, 2025, 04:58:40 pm
content: After replacing the PD817 diode, the laptop turned on and gave the picture on screen.
dell inspiron 1720  backlight - Page 1
Forum section: electronics / repair

author: m3vuv
author_rank: Super Contributor
timestamp: January 30, 2022, 11:00:02 pm
content: Hi all i have a dell inspiron 1720 lappy about 3 months ago the backlight went out,first i fitted another screen and that lasted about 5 mins before it did the same,luckily i had another spare screen so fitted that and all was fine untill a few days ago and the same problem !,my question is would it just be down to age or could a faulty inverter kill the backlight tube?.tia

author: m3vuv
author_rank: Super Contributor
timestamp: February 02, 2022, 12:19:27 pm
content: can no one help on this,as i dont want to replace the screen just to have the inverter possibly nuke the ccfl! .

author: abdulbadii
author_rank: Frequent Contributor
timestamp: February 03, 2022, 06:41:58 pm
content: http://www.laptoprepair101.com/replace-laptop-backlight-ccfl-lamp/
dell inspiron 1720 random turn off - Page 1
Forum section: electronics / repair

author: p.larner
author_rank: Frequent Contributor
timestamp: February 26, 2024, 10:25:53 am
content: i have a 1720 running win7 64bit and a t9500 cpu+ 4gb ram,it has started shutting down at random,i assumed it was overheating due to the cpu upgrade,i cleaned the heatsink+ replaced the thermal paste,it made no change,i notice tho if i remove the battery its fine,its a chineese replacement battery about 6 months old,is this a common issue,is there a fix?.

author: tunk
author_rank: Super Contributor
timestamp: February 26, 2024, 02:11:59 pm
content: If the new CPU draws more power than the old, then the PSU could be marginal.

author: p.larner
author_rank: Frequent Contributor
timestamp: February 27, 2024, 02:48:29 am
content: did i say it is ok on mains with the battery removed,it only does it on mains power with the battery in the lappy.
Dell Inspiron 5321  - Page 1
Forum section: electronics / repair

author: MarkBob
author_rank: Contributor
timestamp: August 31, 2021, 02:02:26 pm
content: Have Dell 5321 which has gone on the blink.Replaced the hdd and ram but getting a clicking sound which is not from the hdd and it says no boot media found.I have made a win10 bootable usb and as it get to where i want to install ,there is no drive available.i have checked in the bios and the hdd is not showing.i have tried looking for drivers on the Intel website, downloading and installing on the bootable drive and still have no luck...........i am hoping that someone on the forum has had the same issue and solved it
dell inspiron battery charging issue - Page 1
Forum section: electronics / repair

author: m3vuv
author_rank: Super Contributor
timestamp: February 02, 2021, 09:26:09 pm
content: Hi all this is also posted in the general computer section,hope thats ok,i have a dell inspiron 1720 lappy,it runs an upgraded 2.5ghz cpu 3 gig of ddr2 ram and a 256 gb ssd hard drive,after doing the upgrades about a year ago,i brought a new charger for it and got a 9 cell battery,tbh it was used %99 of the time plugged in,recently on boot it says cant determin the power adaptor,please insert a 90 watt or higher power adaptor,press f1 to continue etc,trouble is it runs slow and the battery icon says plugged in not charging,,do you think its the battery or power adapter,i have a battery tab welder and a few 2500mah lion 18650 samsung cells,i heard if the battery controller board id disconected from the cells it fries it,any advice how to sort this?,btw im using win7 32 bit,cheers in advance

author: m3vuv
author_rank: Super Contributor
timestamp: February 02, 2021, 10:38:09 pm
content: Well i think i got it sorted,i checket continuity from the barrel jack center pin(data) black colour wire to the charger pcb,it was o/c,stripped the plastick from the barrell conector jack,the black wire should of been soldered into the middle of the center pin,it wasnt,looks like crappy non existant bad chinky qc,it looked like it had just been tacked on the side of the pin and not inserted into the center of it and flooded with solder,its saying its charging now,happy days!

author: ttx450
author_rank: Regular Contributor
timestamp: February 03, 2021, 12:18:13 am
content: hope you got itmost laptops I worked on fireup w/o battery. try that for a test

author: Sceptre
author_rank: Regular Contributor
timestamp: February 03, 2021, 03:44:30 am
content: This is the all-too-common Dell laptop charger ID failure. Fortunately yours just had a bad interconnect rather than a blown OneWire EPROM:http://www.laptop-junction.com/toast/content/inside-dell-ac-power-adapter-mystery-revealedMore:https://hclxing.wordpress.com/2014/02/06/hacking-the-dell-laptop-power-adapter/
Dell latitude e5440 shutdown after 3 sec - Page 1
Forum section: electronics / repair

author: hpibmx
author_rank: Regular Contributor
timestamp: November 09, 2021, 08:41:43 am
content: Hi,I put my laptop on sleep for few days didn’t wanna miss where I left.Yesterday just pressed power button came on high fan and shuts down. Just all of sudden Sutton on my table.I’m repairing phones and tablets. Not experienced with laptops.I’ve look around motherboard for short didn’t really find anything.What would be the cause?Thank you.

author: mikerj
author_rank: Super Contributor
timestamp: November 09, 2021, 10:43:05 am
content: Go through the basics, remove memory modules (ideally one at a time if there are two), hard drive etc. and see if behaviour changes.

author: hpibmx
author_rank: Regular Contributor
timestamp: November 09, 2021, 01:50:23 pm
content: Sorry forgot to mention yes I’ve done all those. Still the same

author: abdulbadii
author_rank: Frequent Contributor
timestamp: November 09, 2021, 02:06:53 pm
content: thermal paste age ? feel the heatsink if not hot ~85 C so overheat too soon

author: amyk
author_rank: Super Contributor
timestamp: November 09, 2021, 02:33:26 pm
content: Unplug, remove the battery and hold down the power button for ~30 seconds to drain any residual charge for a true cold reset.OEM model is Compal LA-9832P. You'll find the schematic if you search for that. Power rails and sequencing information can be found there.

author: McBryce
author_rank: Super Contributor
timestamp: November 09, 2021, 02:56:14 pm
content: Check the PCB for cracked ceramic capacitors, especially around the area of the power switch. I've seen this on several laptops that had the same symptoms.McBryce.

author: hpibmx
author_rank: Regular Contributor
timestamp: November 10, 2021, 12:00:58 am
content: Yes correct about 4 months old. And a free diagnosing I put them back to prevent quick overheat. Thank you

author: hpibmx
author_rank: Regular Contributor
timestamp: November 10, 2021, 12:04:19 am
content: Quote from: amyk on November 09, 2021, 02:33:26 pmI’ve done that too, yes that’s correct and have downloaded the schematic was looking for brd file as well but I guess no need. I’ve looked everywhere done my measurements didn’t find any short at all. On main power rails. Around cpu around gpu. Lower resistance but no short at all. I’ve 3.3v present 5v and 19v.

author: hpibmx
author_rank: Regular Contributor
timestamp: November 10, 2021, 12:08:59 am
content: Quote from: McBryce on November 09, 2021, 02:56:14 pmOkay I’ll go through again and look closely but really couldn’t find any faulty cap.