Is this a PSU issue?

[Cthulthu]

Hey guys, I hope someone here can help me with this. I'm starting to go crazy!

I've been having issues with starting my computer. It started weirdly with me trying to install a new heat sink and getting thermal paste on my CPU, cleaning it off, putting it into my motherboard and installing the new HSU to then find my PC turning on for 5 seconds before crashing. I have an ASUS 990fx and the red light near the 'usb bios flashback' text turns on, then off, and then turns on just before the system crashes.

I figure I didn't clean the thermal paste off properly but after a few attempts to try and clean it more thoroughly, I give in and just buy a new cpu and motherboard (the exact same parts, fx 8350 and 990fx) I've now put everything back together but I'm still have the same issue. As I'm rebuilding the computer, I haven't installed the gfx, the ram or anything else (to ensure none of those things are causing me this grief) It's just the PSU, the CPU and various fans, on and off switches, USB plugins/audio. FYI - I'm not getting any motherboard audio to help me work out the issue either.

I've unplugged the power going to the CPU and when I do this, the computer doesn't crash. It's obviously not doing much else, and the red light is a solid red light which I assume is the case because it doesn't detect a CPU.

All I can assume now is that for some reason, the 8 pin connector which powers the CPU is not working despite the rest of the PSU seemingly working fine. Can anyone help me confirm my suspicions or suggest a way of narrowing down the cause of my problem. I really can't imagine a brand new CPU and motherboard is causing the same exact issue as the previous...but I want confirmation before I blow another £100-200 on a PSU.

 

[brispuss]

First check thoroughly that the pins and pads on the CPU and its socket are not damaged, bent etc. And make sure there is no dust, dirt nor debris of any kind on or amongst the pads and pins.

If all seems OK, then reseat CPU and its cooler carefully and evenly.

If still having issues, then could try measuring PSU voltages at the end of connectors using a digital multimeter while the PSU is connected to the motherboard. But this procedure may not necessarily pickup all PSU faults.

If skipped the previous step, or PSU measured voltages seem OK, then try the PSU in another computer, and/or try another known working PSU. Borrow computer or PSU from friend or neighbor etc if necessary.

 

[Cthulthu]

Any other suggestions? I'm not going to have a chance to test any of this until tomorrow so more feedback would be appreciated.