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  1. #1
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    Immediate shutdown after powering on

    I have a homebuilt tower that is about 2 years old and has functioned fine since I put it together. One day last week, I powered on one morning and after a few minutes the box shut itself off and pushing the power switch did nothing. I figured Power Supply, so I bought a new Antec 650W and hooked it up - when you power-up, all the fans run for about 1 second, then it shuts down. If you turn off the main on-off switch on the power supply, wait about 30-60 seconds, turn on the power supply switch and then push the power switch, the same 1 second fan run, then off again.
    After doing the obvious of reseating all the power cables, graphics card, and making sure I could not see any shorting wires the problem was still there.
    I thought then that it was the Mainboard, but replacing that with a new one also did not solve the problem.

    I am pretty much stumped - has anyone seen this sort of thing before?

    [EDITED WITH UPDATE]

    Since this seemed so much like something was "shorting out" at power-up, I removed the mainboard from the case, laid it on the insulating foam it comes in the box with and reconnected only the essentials (such as CPU fan, DIMM modules, graphics card) but not any HDD or CD drives, USB ports etc. It powers up and stays on just fine. Connected the HDD and again it worked fine (as far as staying powered - I cannot tell whether it is actually going through POST or not). Then I laid the MB on top of the stand-offs in the case, not screwing it down, and it shut off again! I put the foam under the MB and laid it on the stand-offs and voila, it works. I guess something is touching somewhere, but I am not sure what or where. Maybe I will try insulating stand-offs and see if this helps.
    Last edited by mricks01; 2012-11-02 at 09:13. Reason: Updated info
    Mike
    I can always use good information

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  3. #2
    Super Moderator jwitalka's Avatar
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    You can also get insulating washers to go between the MB and the stand offs.

    Jerry

  4. The Following User Says Thank You to jwitalka For This Useful Post:

    mricks01 (2012-11-03)

  5. #3
    Silver Lounger Banyarola's Avatar
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    Make sure the standoffs for the motherboard to the case are in the right places..

    I had the same thing happen and discovered I had one misplaced standoff that was touching the printed circuit on the motherboard.
    "If You Are Reading This In English, Thank A VET"

  6. #4
    5 Star Lounger
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    If you have any standoffs that do not line up with a mounting hole on board remove it as all stand offs should have screws in them.
    Otherwise you could do a long winded test by removing a standoff one at a time testing after each removal to find which one is causing the problem.
    Maybe one of the standoffs is too wide allow it to reach circuits. Or has accidently got fitted with a metal washer.

    At least now you have a spare PSU and Mobo.
    Last edited by curiousclive; 2012-11-03 at 04:53.
    Clive

    All typing errors are my own work and subject to patents pending. Except errors by the spell checker. And that has its own patients.

  7. #5
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    Quote Originally Posted by jwitalka View Post
    You can also get insulating washers to go between the MB and the stand offs.

    Jerry
    That is exactly what I wound up doing Jerry, and it solved the problem. I still cannot figure out why something like this would occur after about two years of working fine, but such is life
    Unfortunately since I was not able to replace the MB with the same brand or model (socket 775 mobos are rare these days) I couldn't get Windows to work. It went to blue screen right after POST (something about drivers) so I have to do a complete reinstall.

    I really hate computers some days.
    Mike
    I can always use good information

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