mobo repair\advice

[basscleff]

Hi all, in the event your motherboard does die, and you cannot visibly verify that a cap has gone bad, are there any other tutorials here for troubleshooting motherboard/electronics repair?

Specifically, VOM meter usage, ohm measurement, impedance, capacitance measurement etc. Maybe a quick how to for locating the root of the problem - when it's "visibly" seen?

thx
would appreciate some links etc.

[kc8adu]

Re: mobo repair\advice

search for vrm testing and follow it.
often no post is due to vrm death brought on by failed caps.

[Spacedye69]

Re: mobo repair\advice

Would VRMs apply to a working mobo that was "accidently o/c'd" and now won't do anything? No POST, no beep, no light. All other components, including processor, tested good. BTW, found this site while searching for repairs for other mobo with random reboot. WOW! A lot of bad caps and it still ran most of the time. Great site!

p.s. "It's Great-n-Dayton"

[Spacedye69]

Re: mobo repair\advice

p.p.s. Dead mobo is A7V333, Nichicon H* and OST caps look good. Are the toroid cores suppose to be black? Rest I've seen are white or green. Wire looks good.

Mobo with bad caps, EP-8KTA3, all GSC.

[linuxguru]

Re: mobo repair\advice

Replace all the GSCs and the random reboot problem should disappear.

On the dead motherboard, try recapping all the caps near the CPU/VRM, as well as any on Vsb. I haven't seen a bulged OST yet, but it's possible that they vent through the bottom seal and dry out quickly.

[Spacedye69]

Re: mobo repair\advice

Was just looking at it again, and one of the caps(Nichicon HM) is tilted. Do they tilt for any reason other that bad(assuming machines never assemble anything wrong!). Cap is in the middle of FETs and toroids. Thanks for the reply.

[linuxguru]

Re: mobo repair\advice

No, it can tilt during assembly or later, when the heatsink is installed, etc. But Nichicon HM(M)s have had issues, so recap that one anyway.