Computer wouldent power on after being repaired try serveral things could it be the cpu blown up?

i have an amd le processor that was in an etower emachine. Was supposed to have windows 7 on it after a repair but was sumhow not working at all so i removed the old psu put it into another computer and i got nothing for power so i figured stock psu was bad. A month later i replaced with another psu was only a 20 pin i herd noise now when i powered it on figured maybe video is shot replaced nothing . After that i had remebered something about amd processors being fussy about runnin wit anything below like 325 or 350w so i said screw it then i ripped out the big dog a 650w psu and installed it nothing was working at that point no fans nothing so i question some plugs being loose i unplugged the 4 pin connector plug that was near the cpu i powered on i hear fans now. so it was at that point i was scratchin my head. I said well i got a newer amd motherboard hanging about am3 backwards compatable so i popped the old le chip into it and hookedall the plugs up and i got nothing so once again on the new board i go unplug the 4 pin plug power on bingo fans turn on but yet the same no video lead me at this point to believe the cpu is junk??? is it possiable that the original board is still good and would work with another chip. The newer board was tested with a quad core and worked fine so i do know that one board used was working and both boards without the 4 pin connected just 24 pin showed signs of fans working