Boot Problem

Yes i have a boot problem...
My recently built computer will start without the 12v connector (or whatever you call it, im 14) by starting i mean fans come on, but then nothing else happens my cpu led on motherboard (asus p7p55d-e pro) just keeps blinking, checked manual basically just states that something is wrong with cpu,i then put the 12v in and nothing happens at all when i press the power button. Anyone know why this is happening or how to fix it.
Thanks Scott
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  1. This could be a faulty power supply, or a faulty motherboard a quick test would be to substitute the power supply with another one. If it is not the power supply then you should strip the motherboard out of the case and power it with everything removed except the CPU, and see if it powers up if it doesn’t then remove the CPU if it then powers up then you may have a faulty motherboard and a faulty CPU. (Worse case)
  2. The 4/8 pin 12 volt connection provides power to the CPU. If it is not plugged in, you have no CPU power, and your system won't start.

    And you need the CPU present to boot.

    Work through our standard checklist and troubleshooting thread:

    I mean work through, not just read over it.

    Breadboard (build the system without the case) - that will isolate any kind of case problem.
    Breadboard with just motherboard, CPU & HSF, case speaker, and PSU first.
    You do have a case speaker installed, right? If not, you really, really need one. 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. It's a low voltage, very low power connection. So i's safe.

    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.

    To test the PSU, 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. You can carefully probe the pins from the back of the main power connector.

    The motherboard can only be tested by substitution. Likewise, the CPU, but it is seldom the problem.
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