Power issues with eMachines eTower 400i3

[wuneyej]

A coworker complained his home computer was making a lot of noise and would occasionally restart itself, so I offered to have a look. Both the power supply and processor fans were making pretty severe grining noises, so I replaced them both.

When I booted up the machine, all was quiet and well. When I did a restart through Windows, it worked perfectly fine, but when I shut the computer down and attempted a cold start I'd get nothing. No beeps, no video, just plain nothing.

Through trial and error I figured out the only way to start the computer was to unplug the power cord from the power supply, then while holding in the power-on switch on the front (wakeup switch I think it's called?) I'd plug the power cord back in to the power supply and get a successful boot.

Could the problem be the motherboard itself? The wakeup switch? Something else? I'd really appreciate any advice.

Thanks,
JP

 

[wuneyej]

Some additional info...

I just spoke to the owner of the computer and he said he's had to use the same procedure for starting the computer for a long time now, so the source of problem should be something other than the new power supply and fan.