ive had a ps that all the fans, drives, and the led mobo light all came on. i borrowed a buddies comp to swap cpu, mem, and stil the same problem. so i decided to swap the ps. lo and behold it worked, so i thought, ok, its the ps. i put my ps back in so it wouldnt just be laying around until i could pick up a new one. for the hell of it, i hooked it up and it worked!😕
so i figured maybe there was a short and i fixed it unknowingly when swapping all the parts. comp was good for 2 days, until i turned it off. the next time it tried to turn it on: same problem. so since my old ps worked after the swap, i thought it couldnt be that. i bought a new mobo, no go. new cpu, no go. borrowed a stick of ram, no go. finally broke down and bought a new ps, and havent had a problem since.
now i always swap the ps first and advise everyone else to also when they have those symptoms. it just threw me off when i put the ps back in, and then the comp worked. ps can be a tricky lot.