Extreme6 cpu power connector issue

[terdferguson]

Alright all here's the specs.

Intel i3770k at 4200 mhz
asrock extreme6
no gpu yet
8 gb corsair vengeance

You'll notice I didn't list the power supplies...

So the build started with a corsair hx750. PC would power off randomly. No blue screen, just off. It would take a few times pushing the power button to restart and I would often have to hit the power switch on the PSU itself a few times. PC would not wake from sleep, but would turn off instead.

So, I was at the store the other day and I bought a new antec 550 cheapy thing to see if I could solve the problem. This psu had a cpu power cable that was two 4pin connectors that could fit together in one 8 pin slot. I tried the 8 pin first and nothing. Then on a whim I tried just on of the 4 pins and it worked. Sort of, had trouble after powering down. Couldn't replicate my results.

Next I went and pulled the old no name psu out of my asus desktop. It only has a 4 pin connector. IT WORKS EVERY TIME.

Could this be a mobo issue? Is it possible that half the cpu power connector is burned out? Both expensive psu's that have 8 pin connectors dont work at all, but one 4 pin works sometimes and the really cheap 4pin works all the time. What's going on?

[- wardog -]

Remove it from the case and while outside the case and with it resting atop the motherboard box try and replicate this issue.

[- wardog -]

... 4200??? On an unstable system???

Have you tried clearing the CMOS?

[parsec]

Is the HX750 a new PSU that you've never used before?

Just to check, the 8 pin CPU power cable you're using is the hard wired, non-modular cable?

A four pin CPU power connector should be connected to the four pins on the right side of the eight pin mother board connection.

It does sound like there might be a problem with the eight pin connector on the board. Or specifically, the four pins on the left side of the eight pin connector. If you tried the four pin connector on the HX750 again and it worked, that could indicate a problem with the other four pins of that connector on the board.

Trying the mother board outside of the PC case as wardog suggested would eliminate any grounding or shorting issues.