Beginners repair of a sound card - Page 1
Forum section: electronics / repair

author: haggar
author_rank: Contributor
timestamp: March 24, 2016, 07:35:14 pm
content: Hey all,First time posting, so sorry if I say something stupid!I'm a computer engineer by trade, but I've decided to take up electronics as a hobby, and in front of me is a broken PCI express 1.0 sound card. Now I realise this is probably a bit (lot) advanced for me, but it's in front of me, it's broken, so I thought it would be a fun project to take a look at. I'm not too worried if it never works again, but I figured it would be fun to take a look at it, give my new multimeter and soldering tools out for a spin, and see if I can learn a few things.If the card is in the PC, it refuses to boot, doesn't even make it to POST, and when the card is removed, everything is fine. On visual inspection the card appears OK, in that there are no scorch marks, bulging or leaking electrolytic caps, no blown traces, everything visually looks OK.My question is this; what's a good place to start when attempting to figure out what's wrong with the card, or any piece of electronic equipment for that matter. Like I said, I don't mind if it never works again, it would just be a fun learning experience to run some tests on it and see what I can learn/figure out.I've got my multimeter at the ready, any suggestions or ideas would be greatly appreciated.I look forward to hearing from you guys, and hopefully I'll be pretty active on here.Thanks

author: SAUL BRITTO
author_rank: Frequent Contributor
timestamp: March 24, 2016, 08:53:12 pm
content: Quote from: haggar on March 24, 2016, 07:35:14 pmIt looks like a short (If the card is in the PC, it refuses to boot,) Look at the +B line of the board,maybe some mosfet in bad condiction.

author: Kleinstein
author_rank: Super Contributor
timestamp: March 24, 2016, 08:53:51 pm
content: This looks like a rather difficult repair. So unless it's a very special card, it's hardly worth the risk of damage to the motherboard. Chances for a successful repair are slim.From the symptoms there are two possibilities that would come to my mind:1) some of the bus signal are not handled correctly and thus block the bus - essentially no chance to repairmaybe have closer look at the part used for bus interfacing. If nothing visible - forget it.2) some power supply is shorted - candidates are some of the many small MLCC caps. One could at least check the supplies - likely solder wired to the few supplies used, carefully check with a DMM when running. If a missing / shorted supply is found there is a slight chance of finding the short, if you have suitable instrument (e.g. power supply and sensitive meter to see voltage drop on lines).

author: Shock
author_rank: Super Contributor
timestamp: March 24, 2016, 11:10:05 pm
content: I found your problem, you need the PCI version not the PCI express version.

author: SaabFAN
author_rank: Frequent Contributor
timestamp: March 25, 2016, 02:02:38 am
content: Easiest way to find a shorted part is to look for any hotspots on the card once the PC is turned on with the card in it. These should get very hot very fast (burns your skin if you touch it).If there isn't any hotspot, the next step would be to check if the on board regulators are feeding the correct voltage into the Soundcard-IC. You should look for 3.3 and 5V. Maybe there's also a 2.5 or even 1.8V rail, but I doubt that on a sound-card. If you have a scope, you could also look for oscillations on the Supply-rails.From my personal experience (compare working / new PCs to non reliable ones) a 2 to 3 division wide trace at 50mV/div at 100 or 50µs/div is okay. Higher ripple-voltage or signs of oscillations looking like, for example, a 1.2kHz 300mVpp sine-wave aren't.If you can't find any fault with the power-supply, the only remaining suspect is the Soundcard-Chip itself, which turns the card to nothing more than a paperweight.

author: airlomba
author_rank: Contributor
timestamp: March 25, 2016, 10:36:42 am
content: Hello,Have you tried your card in another slot of your motherboard. If the problem persists, try it in another computer too. This is just to make sure the problem is in the soundcard and not in the motherboard...Good luck,Best regards,Emmanuel.

author: haggar
author_rank: Contributor
timestamp: March 25, 2016, 11:41:55 am
content: Thanks all for the input, I'll give your suggestions a try!I've tried the card in different PCI slots and different PCs, the same thing happens.

author: EPTech
author_rank: Regular Contributor
timestamp: March 25, 2016, 12:26:49 pm
content: Hi there,As suggested, a power supply problem may be at hand. Even if the bus is occupied, the BIOS should still do something and at least show a splash screen of some kind or at least beep the system buzzer if it detects a basic IO problem.If you have a Multimeter the simplest of things to do is bring up a PIC or PCI-x pin-out and start looking for shorts on the power rails. Put you DMM in contnuity test or ohm range, put the COM probe on a GND pad of the edge connector and check the power pads one by one. Additionally you can also check the power rails one to eachother. There should not be a short anywhere, except between the GND pads and concurrent power rails of course. Let us know your findings.

author: haggar
author_rank: Contributor
timestamp: March 25, 2016, 12:59:37 pm
content: On the topic of finding a short, I've got a few rolls of thermographic paper from some old PDQ credit card machines (the paper onto which the receipt is printed). Do you think that stuff could be used to help identify which chips (if any) are getting super hot through a short? Like I put some paper on the board and checked to see which components got the hotest? Or is that a dumb idea? Thanks

author: deadlylover
author_rank: Frequent Contributor
timestamp: March 25, 2016, 01:21:29 pm
content: You may have to try powering it with a current limited lab supply to look for any toasty parts, I think the computer PSU will just cycle on and off, or just stay off after the over current protection trips. I had a similar thing happen just the other week with a graphics card.But first check for shorts to ground on the power pins like the other members said!

author: TiN
author_rank: Super Contributor
timestamp: March 26, 2016, 12:13:16 am
content: Usually motherboards don't have overcurrent protection on PCIe slots power rails, meaning anything that have major short on input would trip main PSU protection or just get fireworks and sparks if short in the thing up in resistance. Having that said it's possible that card still have power issues, so check input and output on any regulator ICs you may find on card. Often its LM1117 or similar there.Usually good rule to get forum help - provide as much details as possible, so folks around know what we talking about. Good hires photo of front face and bottom could be a great help for further directions.Now, not knowing what is even card model but knowing it's PCIe one, I would check clocks out of onboard crystals. For that you will need scope or frequency meter. Sometimes (but rare) clocks fail.Check for any damaged/delaminated parts especially SMD caps and resistors. It can be hard to see with naked eye, but if critical passive got open/shorted it could make card sput.Check PCIe AC blocking capacitors (easy to spot those, as they are on differential pairs just next to PCIe edge connector. They are in pairs there).Often there is SPI or I2C EEPROM on soundcards, so check if those still have data. For that you might need desolder the chip and put on programmer. Some cheap ones like TL866 are handy tool for repairs. Get one if you don't have it.