I was on my PC today and I noticed one of the USB connectors had come out of the back of the PC,the insulation inside the USB plug had broken and when I tried carefully to put it back in the outer earth touched one of the pins. The PC just switched off instantly. Thought it would of been the fuse in the mains plug when i wouldn't boot back up but that is ok. I have put my meter across the PSU power in and that is ok, the switch is switching power ok. There is a fuse on the circuit board of the PSU and that looks ok. So where else should I be looking or does anyone know where to go straight to. I'm looking online to buy a new PSU but not sure if this is my problem.
The USB was a 4 port PCI slotted in, hope it isn't the MB. The PC is 5 years old now and all I have done to it so far was swap the MB out about 6 months ago. Been lucky really. I've had laptops that have only lasted 12 months and 1 day. (Just out of warranty).
I checked the socket and all the pins are in fresh air "so to speak". The PSU is ordered and I will take it from there. I understand what you mean about blowing the next PSU. I will isolate that USB socket for the time being.