For motherboard, symptoms include:
- Motherboard doesn't power on.
- Motherboard powers on, fans spin, but doesn't POST.
- Motherboard powers on, fans spin, POST succesful, operating system loaded. However one or more caps on the board is clearly bulging.
Before attempting to fix power supplies, make sure to take necessary precautions. One can get a nasty shock touching some components. After unit is powered off, the large cap on the high voltage side will still hold a charge for some time.
For monitor's power supply, symptoms include:
- Plug in power to monitor: "power on" indicator LED turns on briefly, then turns off. No display.
- Plug in power to monitor: "power on" indicator LED turns on, display turns on briefly, then unit turns off.
For desktop power supply, short the green wire to a black wire to turn on the PSU without a motherboard. http://aphnetworks.com/lounge/turn_on_psu_without_motherboard_the_paperclip_trick
Symptoms include:
- low 12V (yellow wires). From experience, 11.9V or below is "low" if the PSU has no load.
- low 5V (red wires). Lower than 5V is "low" if the PSU has no load.
- low 3.3V (orange wires). (rare)
- high -12V, -5V. (very rare)
