Damn .... I recently had a ( well I thought ) problem with a PSU that was RMA'd to Scan and replaced.
I'm afraid the new PSU has exactly the same symptoms. In fact its not the PSu that has the problem !!
The symptoms were :
A very strange noise not unlike the sound a 56k modem makes that increased and decreased in pitch depending on what the pc was doing at the time. It even happened tabbing through the BIOS pages.
When the new PSU did the same I took it out of the case and ran it on the desk.
The noise sounds like it coming directly from the CPU although I cant see that being the case. That leaves one of the caps around the CPU mounting. ( Asus P5KC ).
I've tried listening with a cunningly made paper funnel but cant zero in exactly on the noise.
The thing is it's taken me hours getting the case tidy with all the cables routed and tied just how I like it so I really dont want to RMA the Mother Board. At least not yet.
Whats the advice ? Could it be a faulty cap. Could it fail catastrophically taking everything else out with it ? The system is running fine apart from the noise issue.
After all I have a years warrenty and I would like to enjoy my new kit for a while before having to rip it to bits again.