Computer powers on then off straight away

[Nervousenergy]

Hi all,
I've recently built a new rig, specs follow:

Intel i7 920
Asus P6T deluxe V2
3GB 1600 DDR3
Nvidia 8800GT
2 x standard 500GB sata drives
ASUS D2X soundcard.
700W PSU

Has been working fine at clock speed of 3.2GHZ for days now, suddenly it powered off by itself. It keeps trying to power on, as in everything lights up and fans kick in but the after half a second it goes off again. Then again. etc. I've had a bit of a mess around, and if I pull out the secondary MoBo power plug (4 pin) everything comes on and stays on, although I get no display on at all so I don't know if there are any error messages. Once the plug goes back in the on/off cycle starts again. I've cleared the CMOS which did nothing, and I've tested the graphics card which is working fine. I have a spare 600W PSU which I've tried but I can't get it to work at all with that, not enough power! I was wondering if anyone can make any suggestions? Should 700W be enough? Figured if it was the board or chip I'd get some sort of error message or beep code at least. I'm going to try removing the RAM and see if that works. Will post back. Thanks in the mean time for any help!

 

[Hefemeister]

I run mine on a 750 which is overkill. 700 should be fine.

Did you just use the 4 pin 12v or use the full 8pin?
I would use the 8 pin if your psu has one.
You are back at stock speeds correct?
Did you plug a case speaker into the front panel connections so you can hear the post beeps as the p6t deluxe has no built in speaker?

Double check all of your power connections into the board.

 

[Nervousenergy]

Hiya thanks for reply. I assume I'm back at stock speeds as I've cleared the CMOS RAM but since I can't get a picture I cannot verify. Power supply doesn't have an 8 pin no, so 4 pin is the only option. And yeah I've got a speaker on my case thats plugged in and working, as it screams when I unplug the graphics card power supply. Hmm I'm going to strip it down and rebuild from scratch I think. Will see what happens there.

 

[Nervousenergy]

ok tested all but MoBo and CPU and I've rebuilt on a plastic board outside the case so its not a short. Same thing occuring. Must either be MoBo or CPU you think?

 

[Hefemeister]

with all of the testing you have done I would lean in that directions as well.
Can you get a rma on the board and cpu?

 

[Slaymate]

Try one of these

Newegg.com - APEVIA 9.5" 4 Pin P4 /12V to 8 Pin P8 /12V Power Supply Converter Cable Model CVT48 - Cables

 

[Nervousenergy]

I'm thinking its the MoBo. I'm sure if the MoBo was working fine and something was wrong with the CPU I would still get power at least, and most likely a message asking where the **** the CPU was... or something to that effect. You guys think the same? I got the MoBo and CPU from different suppliers so I need to send the right one back to get tested and replaced, and I get charged if its not faulty! ha ******n this is a pain. Oh and thanks I've ordered a cable adaptor

 

[MIDItheKID]

I am having the same exact problem with a P6T Deluxe (v1) and a i7 920. Ended up RMA'ing my Mobo and PSU, and i'm still having the problem. Have you figured anything out yet? This is driving me insane. My computer has been out of commission for about 3 months now and i'm pulling my hair out trying to figure out what the problem is.