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My machine has started shutting itself off after a few minutes on, everything goes off.

A few seconds (3-5) after everything has stopped the lights come back on, the cpu fan and gfx card come on again. They spin for a second, then everything goes off again. A few seconds later same things happens again, light come back on, fans spin for a few seconds then go off. This repeats seemingly forever.

If I leave it for a while I can power the machine back on for a while and it will boot again. It will then stay on for a little while again before power off. Rinse and repeat.

Is this likely to be power supply or something else? The machine has been up and running for a couple of years before this.

EDIT

from the bios:
+3.3v : 3.152
+12V : 11.731 and seemingly going down 11.668 -> 11.604
CPU Temp : 31C
CPU FAN Speed is ok

I left the machine on in the bios screen to see if it went off just in bios and after a few minutes it powered off.

Does this point to power being the issue?

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1 Answer

up vote 0 down vote accepted

I think you should boot into the BIOS and check what temperature your CPU is running at. This sounds like an overheating problem, and the CPU is the easiest thing to check. The fans might not cool the processor correctly, or there could be some other electrical problem with the motherboard causing the CPU fan to fail.

If the CPU works correctly, then the power supply might be the culprit. If you have another computer, then try to borrow the PSU from that one (which can be done without removing it from the case of the second computer).

Worst case scenario, you still won't find anything. Then I'd recommend stripping the motherboard of components (RAM, graphics cards, network cards, etc) to the minimum required for it to boot. If this fails too, then buy a new motherboard. I've been in the same position as you before, and this methodology saved me from buying unnecessary components. It turned out to be the motherboard in my case.

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added a few more details after booting into bios. –  Sam Holder Jan 13 '11 at 23:37
    
The information from the BIOS diagnostics seem just fine. Your next step (just to make sure you'll be replacing just the right component) is to strip the motherboard of all components which your computer won't need to boot. Remove unneeded harddrives, all but one memory stick, the graphics card, etc. Also, try two separate RAM sticks, one at a time. This is hardly a RAM issue, but you'll want to know for sure to avoid spending money where you don't need to. –  cmbrnt Jan 13 '11 at 23:39
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