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I bought a new computer and I'm almost ready to send it back to the shop. Here are the specs:

  • Motherboard: Asus Crossfair IV Formula
  • Processor: AMD Phenom II X6 1100T Black Edition
  • RAM: 4 x 4GB CL9 1333Mhz
  • Graphics Card: Sapphire Radeon HD 6970
  • Hard Drive: Western Digital Caviar Blue 500GB
  • Power Supply: Corsair Enthusiast TX850

At this moment (after trying many different things) the motherboard sits outside the case (nothing connected to the case), on a carton board. Connected to the motherboard is the 24 pin power cable, the 12v power cable, the processor, the graphic card, one RAM module, the hard drive and the keyboard. When turning it on (this motherboard has a built in power button) the screen displays POST and I press DEL to enter BIOS set up, then I touch absolutely nothing else (I barely breathe) and after 5~15 seconds it powers off by itself. In a few occasions it seems to be trying to power on again (the fans go on and a few leds blink) but it doesn't succeed.

I went to the Asus Power Calculator and my PSU should be more than enough.

Sometimes it doesn't even reach BIOS (it displays the logo and powers down).

Thinking it could be a heating problem I turned off the PSU, waited 5 minutes and brought my desktop fan and pointed it to the motherboard, tried again and no change.

Any idea what could it be or what can I do?

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Make sure no foreign objects, such as a screw, are on the motherboard.

Disconnect the hard drive and retry to eliminate that as an issue. Then do the same with the graphic card.

Did you install the CPU by yourself? It might be possible that the thermal paste/grease hasn't been properly applied on the heatsink and the CPU might be overheating. An external fan wouldn't cool it enough in this case.

Try a different power supply if you have one available.

Also swap RAM modules to eliminate that as a possibility.

If none of that works, take it back.

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+1 for good answer. This behavior screams 'CPU heatsink isn't mounted properly' incidentally; if you remove the heatsink entirely ANY machine will shut off in 5 seconds regardless of how many fans you point at it. – Shinrai Apr 20 '11 at 17:41
And actually, just remove the hard drive and graphics entirely and see if it'll stay on. (Could potentially be a problem with the PCIe bus or something) – Shinrai Apr 20 '11 at 17:42
Thank you guys for your replies. Following the advise we checked the back of the motherboard and it is pretty warm, right now we lifted it up and the external fan is cooling it to a decent temperature before we give it another try. It seems this could be the problem, so Im happy to have a solid clue. I also didnt want to put the heatsink because it glues the processor, and if I want to remove the heatsink it brings the CPU with it – Purefan Apr 20 '11 at 17:50
I agree this is most likely a bad heatsink another possibility is the system came with a dead cmos battery. – AlwaysLearning Apr 20 '11 at 17:54
@Purefan - Wait, you haven't installed the heatsink yet? Well that's the problem - you don't really have any say in the matter! :) – Shinrai Apr 20 '11 at 18:21
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