I have a Acer Aspire desktop model AST690-UP626A that is making a whistle whenever turned on. From reading on the web I'm thinking it is the power supply a FPS Group Inc model ATX-250PA Part no 9PA250BF00.
Leaving the 20+4 pin connector plugged in, everything seems fine. However when I plug the P4-MB connector in the whistle starts.
I need to know if this could be a motherboard issue or power supply before I go swapping parts on the customer.