PC won't turn on

JVG1023

Distinguished
Mar 1, 2016
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So my PC was working fine for a few weeks after installing a new cpu (AMD FX8350) but all of a sudden I try and turn it on and the LEDs turn on and the fans spin for half a second and then cut off. I figure out that if I unplug the 8-pin cpu cable from the power supply and leave in the 24-pin it works fine and maybe it's just not powerful enough to power up the CPU. So I buy a new power supply (corsair CX750m) hook it all up and the same thing happens.
My rig:
CPU:AMD FX8350
GPU:R9 380
PSU:corsair CX750m
 
Solution
Seems like either a bad 8-pin cpu or more likely a bad eight pin socket for the motherboard. Can you test the power supply on another computer?