How to determine if my PC power supply is broken?

Question

It started off were it would take a couple pushes of the power button for the computer to boot up, it would usually just flash the lights then shut down. Now, I don't get even get that which leads me to believe that it is the PSU except for the fact that the motherboard is still receiving power because the LED light on the motherboard is still on. Any input would be appreciated.
Components:
ASUS A8N-SLI Deluxe Motherboard, AMD Athlon 64 4000+ San Diego CPU, APEVIA ATX-AS520W-BK ATX 520W PSU

Answer 1

http://pinouts.ru/Power/atxpower_pinout.shtml
http://pinouts.ru/Power/atx_v2_pinout.shtml
the first one is for the 20 pin connector, the second one for the 24 pin connector. (I mean the mother board connector). remove it and using a piece of wire (paper clip) short pin #14 (20pin) / #16 (24pin) to the one next to it (#13 or #15 / #15 or #17) or better by colors: green to black! this way, the PS should start (you'll bypass the motherboard's starting circuit) and you'll can see/hear the hard disk(s) spinning and if there is a disc in the DVD/CDROM drive it should spin too for a few seconds. you can also eject/load the optical drive's tray. if the PS works this way for some (say 10) minutes, I suppose it can be declared as OK and the motherboard DEAD.
ELSE, if it still doesn't start or if it's starting and after few seconds stops, remove one by one the floppy/DVD/CDROM/HD molex connectors until either you find the faulty unit or until there is nothing more attached to the PS. if neither in this later case it doesn't start (it's fan should spin merilly), you can dump it to the trash and change it with a new one... it's cheaper than repairing it.

Answer 2

Check also your power switch, it might be defective. You can bypass the switch function by shorting the pins where the wires from the power switch plug in.

Before you declare your motherboard as "dead", try detaching it from its mounting, then powering it up w/out touching anything in the case. There might be a part of the motherboard that is grounded w/ the case and causing an overload of one of the voltage rails. The power supply goes on auto shutdown if there is an overload.

The +5V SB is always ON as long as the power cord is plugged in. The lighted LED could be getting its power from there.

Answer 3

you got a dieing power supply and chances are it will kill more then itself meaning the memory and the mother board in time suggest you replace it as soon as possible