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Asus P2-99B - Attempted repair and failure

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First post, by pete8475

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I said in another thread I'd make a post about my repair attempt so here it is.

I got this board a few weeks back with a blown capacitor, over the weekend I replaced it with a new one ordered from digikey but unfortunately the board still doesn't work. I used some solder braid on the back to clean up the old solder before installing the new capacitor.

When I turn the power supply on the board immediately powers up but does not post. I've tried several known good sticks of ram, processors and video cards. Probably going to just throw it out now, I was really hoping to get this one working.

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  • IMG_0075.jpg
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Reply 1 of 3, by quicknick

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A quick list of suggestions, of course there's more you can do but this comes to mind right now:

If one cap was blown, more could be bad without showing any signs. Careful when replacing, Asus usually have the markings in reverse (big white stripe is the + not the -, fortunately the + is also clearly marked).
I see the board supports both AT and ATX PSUs, try with either.
Carefully inspect the board, especially the back - look for scratches that might have broken one or more traces, look for bent pins touching where they shouldn't.
Check that the BIOS image is OK.
Check output of every VRM on the board.

Reply 2 of 3, by Horun

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Yes you need to replace all the VRM caps if one died. Also: personally have had poor luck with those AT/ATX boards, they seem to fail in other ways besides caps.....

Hate posting a reply and then have to edit it because it made no sense 😁 First computer was an IBM 3270 workstation with CGA monitor. Stuff: https://archive.org/details/@horun

Reply 3 of 3, by pete8475

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quicknick wrote on 2020-09-07, 23:46:
A quick list of suggestions, of course there's more you can do but this comes to mind right now: […]
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A quick list of suggestions, of course there's more you can do but this comes to mind right now:

If one cap was blown, more could be bad without showing any signs. Careful when replacing, Asus usually have the markings in reverse (big white stripe is the + not the -, fortunately the + is also clearly marked).
I see the board supports both AT and ATX PSUs, try with either.
Carefully inspect the board, especially the back - look for scratches that might have broken one or more traces, look for bent pins touching where they shouldn't.
Check that the BIOS image is OK.
Check output of every VRM on the board.

I don't think I really have the patience/skill to replace all the caps on the board.

What I have noticed while looking at it is that there is a big bend/twist to the entire pcb, I suspect it has some damage because of that. I can't see any broken traces or bent pins touching.

I don't actually have any AT power supplies these days, I use ATX power supplies with an adapter for anything that doesn't have an ATX power connector.

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