I support a refurbished Dell Dimension 3000 PC (c. 2004) which occasionally will not boot: no POST or video signal, but the fans will begin blowing and an LED on the mainboard lights up. I believe the hard disk also spins up.
I discovered, after trial and error, the PC will boot after I switch the power supply from 115V to 230V and then back to 115V.
It seems we cannot trust the power supply anymore, but I am curious if someone might provide insight as to why this might occur, from an understanding of the power supply itself? What happens in the power supply when I switch the voltage back and forth to allow the PC to boot?
Everything seems normal while running the PC except for a noisy rear cooling fan.
I believe the power supply came with the Dell, for what it is worth: Dell HP-P2507FW, serial number CN-0K2946-47890-49L-7061, REV A00.