PC shuts off at BIOS

[suklee]

Friend's PC was working recently (although from what he said, the power supply was beginning to go), but after he cleaned out the inside it wouldn't boot anymore.

He got a new Power supply now, and it POSTs but after getting into BIOS, after a few seconds it just shuts off.

Any suggestions? He thinks the mobo might be fried...

 

[Zap]

Make sure the CPU heatsink is seated properly and uses thermal compound. Make sure CPU fan is plugged into CPU fan header.

 

[mindless1]

I second that, powering off after this period is usually a bios safety shutdown due to excessive temperature or no (or too low to register properly) fan RPM signal. These settings can usually be toggled off if you/he is certain there is no problem.

There is also a slight, though unlikely, chance the PSU is flaky and the power level the system is consuming while sitting in the bios leaves one of the PSU's rails outside the regulation limits so it shuts itself down. Usually when that happens, in order to get it to turn on again at all it is necessary to switch off or unplug AC power to the PSU and back on again.