PC Problems - not sure if it's PSU or Mobo or something else-related...

Was asked to fix a 'dead' PC about 2 weeks ago. When I got it, it powered-up AOK and I was wondering what 'dead' meant when it decided to instantly power-off again.

I took everything out and tried each bit in turn - but it was only when I replaced the PSU (with an old spare) that it powered-up again.

So I sourced a new PSU and all seemed well - so it went back to it's owner.

Within 2 days of getting it back, it reverted to it's old tricks - shutting-down instantly after about 10 mins of use. It will not power-on again for quite some time afterwards.

It does this even in the BIOS screen so it's nothing to do with Windows. It does it even with everything but the Mobo connected to the PSU - so it's not an HDD/DVD or anything like that either.

I've checked (using BIOS and Speedfan) and it's not overheating (temps are <35 degrees when it shuts-down) - tho the PSU could be overheating I suppose..

Weird thing is - both old and new PSU are unstable in other PCs too - which suggests both PSUs have the same fault - which further suggests it's the PC/Mobo which is actually frying the PSUs???

Any other ideas?? - I could get the 'new' PSU swapped as faulty and see if it cooks the next one but other then that - I'm out of ideas and thinking this PC is a toaster??

By way of an update, I think I sussed this out.

3 diff. power supplies all failed with this PC - they work AOK in other systems tho.

My conclusion is that the mobo is fried and it's somehow overloading/overheating the PSU. Once it's cooled/reset the PSUs seem fine.

Mobo/CPU now in the bin :)

why bin the cpu as well?

Nothing to say it's not the CPU at fault. Unlikely, but I don't see why it's impossible.

If it would mean sourcing other components to work out, and the CPU/mobo aren't worth much anyway, it's probably not worth the effort.

bulging caps on the motherboard? I've seen this cause all sorts of strange power problems.

No obvious signs of damage on the board - just not worth the time finding another board to test the CPU when it's probably worth £2 on a good day anyway (Athlon x2).

The PSUs have been in other systems since, working flawlessly. The memory has been reused as have the HDDs and DVD - the graphics card (AGP) is in my 'spares' box - the case is rusting outside awaiting a trip to the dump! :)