Computer constantly powers off

I purchased the components for a new machine last weekend. Included are an ASUS P6t SE board, i7-930 CPU, Nvidia 260 VC, 6 gigs corsair memory.

I assembled the components, but for some reason the machine will only stay powered on for anywhere from 5 to 40 seconds before always doing a complete poweroff.

Thinking that I had an underpowered power supply, I bought a new 700w PS from cooler master. Same issue persists - the machine starts to boot, but will turn itself off after a short while. Sometimes almost immediately, sometimes it makes it all the way to the DVD drive trying to load the OS install routine... totally random.

I think there is a bad piece of hardware, but I dont know what it is, and I dont want to return all of it. Please help! Any ideas?
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  1. Best answer
    Unfortunately, Coolermasters aren't the greatest power supplies in the world. So you do not really know if your brand new, out of the box PSU is working.

    The best way to test the PSU is to try it in another similar system. The downside to that is that it could damage something in the other system. Then you have two systems that do not work.

    You have worked through our standard checklist and troubleshooting thread:

    I mean work through, not just read over it. Overlooking something is the cause of most problems.

    Breadboard - that will eliminate any kind of case problem.
    Breadboard with just motherboard, CPU & HSF, case speaker, and PSU.
    You do have a case speaker installed, right? If not, you really, really need one for troubleshooting. If you case or motherboard didn't come with a system speaker you can buy one here:

    You can turn on the PC by momentarily shorting the two pins that the case power switch goes to.

    You should hear a series of long, single beeps indicating memory problems.
    Silence indicates a problem with (in most likely order) the PSU, motherboard, or CPU.

    So, the best bet is to replace the PSU with a known good one of similar power capacity. Brand new, out of the box, untested does not count as a known good PSU.

    Next best thing is to get (or borrow) a digital multimeter and check the PSU.

    Yellow wires should be 12 volts. Red wires: +5 volts, orange wires: +3.3 volts, blue wire : -12 volts, violet wire: 5 volts always on. The gray wire is really important. It should go from 0 to +5 volts when you turn the PSU on with the case switch. CPU needs this signal to boot.

    You can turn on the PSU by completely disconnecting the PSU and using a paperclip or jumper wire to short the green wire to one of the neighboring black wires.

    This checks the PSU under no load conditions, so it is not completely reliable. But if it can not pass this, it is dead. Then repeat the checks with the PSU plugged into the computer to put a load on the PSU.

    After that, the next most likely suspect is the motherboard. CPU's very rarely are bad out of the box.
  2. Best answer selected by cerpika.
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