Motherboard turns on then immediately off

I have read through a million forums about this and no one seems to have quite the same problem.
I have an acer p5n32-sli deluxe mobo with an acer predator case.
The mobo powers on (fans led's etc) but then immediately turns off, no beep codes or anything. i have tried known good psu's, gpu's RAM, the lot. I have just rebuilt outside the case, and noticed that for the fans etc to turn on, the cable that seems to be going to the USB dock on the top of the case needs to be connected, while the cable that goes to the on/off switch doesnt do anything?

If i plug this cable in then it turns on for about a second. If i just touch it and remove it straight away then the fans and LED's stay on but nothing else happens until you fiddle with one of the cables, then it turns off.

The cpu and fan are both seated correctly etc. I cant see any blown caps, and the rails all seem to have to have power (used a meter but a very cheap simple one) but its almost as if there was a short or if no power going to cpu, but if it was a short surely building outside of the case would stop most of that issue if the rails work, and i cant see the cpu going bad overnight. Cmos has been reset and so has the CLRTC.

Any other ideas or options? Much appreciated in advance!
7 answers Last reply
More about motherboard turns immediately
  1. Can u try another PSU?
  2. OK, post your specs...

    RAM: with link please.
  3. have tried 3 psu's two of them known to work.

    Specs are:
    MOBO: asus P5N32-SLI-DELUXE
    GPU: tried PNY GTS450, GTX450 AND PNY G-FORCE 7600
    RAM: hynix 1Rx8

    not sure what the cpu is, compound covered the sticker
  4. Did u do anything new, like upgrading?
  5. no, just unplugged and opened case to clear dust
  6. Any update on this? Have just purchased a P8H77-M and have the same problem.
    Have nothing plugged on the board, only power, and turning on results in the mobo coming on (for less than a second or two) and immediately powering off.
  7. Hi, Usually it's a short related issue (extra standoff shorting the board). Try testing the board outside the case.
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