Computer losing power, failing to power itself back on until unplugged/replugged.

[Eihli]

I wasn't exactly sure which subforum this post would belong in, and I know this isn't exactly a troubleshooting forum but I need help.

Two weeks ago my PC randomly started suffering from shutdowns where it was immediately lose power, and then I restarted it... it would cycle on and off every few seconds until I physically removed the power plug from the motherboard and reinserted it.

First I thought it was the PSU, which is a 1000w Mach, and I replaced it with a smaller 600w and still the issue persisted. There was no smoke or any other visible cue which would lead me to suspect that it was a PSU problem.

Then I thought it was the CPU. I have a Q6600 with a Zalman heatsink. I downloaded speed fan and the temperatures were fine, I never saw them go above 55-65c.

Then I thought it was the motherboard. I bought a brand new EP45 and rebuilt my computer, installed my CPU and installed my heatsink, cleaned off all the dust, new case. etc.

When I went to install the operating system, it started happening again...

Then I tried doing it with different sticks of ram, and still... it persists. The only thing I haven't checked is the video card, but that wouldn't cause a system malfunction or a power cycling problem.

Something is overheating and I don't know what it is.

 

[gimp]

try a different power outlet?
plug straight into the outlet if you're currently plugged into a powerstrip or surge protector?

 

[Quikstrumental]

The only thing I haven't checked is the video card, but that wouldn't cause a system malfunction or a power cycling problem.

You've checked everything else, so try your video card to rule that out as a possibility before we begin assuming it's your power source.

 

[Eihli]

Well it was the video card which is an EVGA GTX 260. My PSU's have internal safety mechanisms where they shut off in the event of either over-heating and over-voltaging.

Both 4x2 molex pins were connected to the card, and it had run fine for 2-3 months, and the fan is still spinning. Anyone know why this is happening all of a sudden? It doesn't appear that the card is defective.