PC won't start up - PSU buzzing

[Guest]

Hi guys,
I was rebuilding a PC today. I am helping out with I.T in a school, so kids were mainly putting it toghether.

When I plugged it in, flicked the PSU switch and the front power switch it didn't turn on. The only sign of life was a strange humming noise from the PSU. I may try refitting it. The children havn't fitted the parts in particyuarly well. Bearing in mind someone so considerally dumped a power brick and a keyboard on top of the motherboard! What can I do to fix this?
It is an Eagle PSU, and quite old
Many Thanks,
AKNerd

 

[Caldrumr]

PSUs are more prone to failure than a lot of other parts, so I would rule that out before you go looking into the motherboard or anything else.
Take the unit out, bend a paperclip into a U shape, stick one end into the opening for the green wire (ON) and the other end into the opening for any black wire (COM). Plug it into a completely separate outlet, and see if it turns on or makes the same noise.
If it makes the same noise, it's time for a new PSU. If it starts up normally, it could still be malfunctioning, so you can check it with a PSU tester or multimeter. If it tests good, start looking at other parts, beginning with the motherboard.