Power comes on for only a second

Just put a new system together, and when I press the power button, fans start for a second, then it shuts back down. No button press will do anything after that.

Here is what I've checked. Power Good signal seems OK. (now way to time how long it takes) It is going high as soon as I press the button.

Power Supply works with a cheap tester.

System will run if I short the Power ON pin to ground, and leave it there. When running, voltages report a touch high, but well within spec. (I don't have second power supply that would handle this system)

I'm 95% sure it's the mother board, but that's the hardest thing to remove, and will disable the machine until replaced.

Suggestions? (mainly other things to try, otherwise away goes the MB)
6 answers Last reply Best Answer
More about power second
  1. Have you connected the 4 or 8 PIN ATX power cable to the motherboard?
  2. Yes. connected those, and the 2 PCIe power cables on the video card. I've also tried removing all fans & drives from the power supply. Same results.
  3. Hi,

    Just to make sure there are no bios glitches going on can you unplug the battery from the motherboard and unplug your PSU power cable, now press your power button several times just to clear any charge, put the power cable back in but not the battery and power on.

    See what happens, if it works then shutdown, turn off and put the battery back in.

    Has fixed a couple of DOA boards for me in the past.

  4. Best answer
    try another psu if you can. it must be a different make. my old amd did this very thing and the psu was fine. i tried a different 1 and the pc came on first time. there was nothing wrong with the original psu it just wasnt compatible with the motherboards phasing. the first 1 was a 2.0 while the second was 2.2 both had 4 pin atx as did the motherboard and both had 20+4 for the main power. so like i say check the psu is compatible as i found not all are.
  5. Just wanted you all to know, it was the power supply. Thanks.
  6. Best answer selected by matthelm.
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