So I can't look for extra mounting stud shorting out the backside or a CMOS reset jumper in the wrong position or a missing CMOS battery. The list is very long and you can find it by going to google and typing in THE DEAD PC.
http://apcmag.com/icute_850_watt_psu.htm is the PSU so if it's dead, it's covered.
I've just upgraded parts in my PC. was a few years old, built it myself then too. Got new motherboard, ram and processor. Connected everything and power lasted literally 1 second, then died and i cannot turn it back on again. So i assumed it was the motherboard at fault, and got it replaced. New motherboard arrives and i have the exact same problem! If i connect my old parts, my 850w power supply has no problem driving all incl an ati 6950 gpu. Now seems to not have power with new parts even without gpu
motherboard: gigabyte z77-ds3h
ram: 8gb (2x4) crosair vengence 1600mhz
psu: Cute AP-850AS (Not cheap in its day)
cannot power this fella on with/without ram, with/without gpu.. please help