Why is my PC power supply randomly shutting off?
The power supply for my PC intermittently, and for no apparent reason, shuts down completely (no voltage on PS-ON). When this happens, if I immediately cycle the power switch on the power supply and then press the on/off switch, the computer starts normally. However, if this happens when I am away from the computer and everything has had time to cool, the above procedure does not work. When I attempt to start by using the above, the panel lights flash momentarily and the power supply shuts down again.
The only way to get it to start is to run a hair drier into the power supply fan for a few minutes, and then it will start. I don't think that it is anything in the power supply that needs to be warmed, but probably something else. I have disconnected everything connected to the motherboard, but nothing makes any difference. It would appear that the power supply is bad, but this is not the case, as I have replaced it with a known good unit, and the problem remains. I would certainly appreciate any help.
This is definitely not my area of expertise, so I asked my friend and colleague Jerry Foutz, who is a power supply guru, about your problem. Here's how he responded...