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New Build won't stay powered on

By daveca5150
Oct 26, 2008
  1. Hello,

    I'm hoping for some help with a new build problem.

    A power surge blew my old psu, mobo and ram. I had it diagnosed by a shop and they told me my CPU was still ok, so I'm reusing it for my new build.

    I put it all together as per manufacturer's instructions and it powered up for about 5 seconds then shut down, then came back on for a fraction of a second before turning off again.

    I tried disconnecting PCI-E card, hard drive and disk drives, same thing
    I tried moving the ram around, tried both sticks by themselves, same thing
    I tried removing the mobo and reinstalling, checking for extra spacing posts that could cause a short, same thing
    I jumpered CLEAR CMOS with a screwdriver for 10 seconds and reinstalled everything, same thing
    I took ram out completey, same thing
    I tried with no fans connected, just CPU and motherboard with both power cables (4pin CPU power is secure and firm), same thing.

    Here's my hardware:

    Gigabyte EP43-DS3L (New)
    Intel Pentium D 945 SL9QB 3.4ghz/4m/800/05A (2 yo)
    Corsair 2x1gb DDR2 1066mhz PC2-8500 C5 (new)
    Antec Case (1 yo)
    Antec Neo Power 550 watt PSU (New)
    ATI Radeon 2600xt (1 yo)

    Hope someone can give me the next step to get this thing working.

    Cheers,
    Dave
     
  2. Cinders

    Cinders TechSpot Chancellor Posts: 872   +12

    Well you've boiled down the problem to either motherboard or power supply. Your testing suggests that the motherboard is bad, but I'd borrow a friends PSU and give it another whirl. If it works then you have a PSU problem and if it doesn't then the problem is the motherboard. Did you take the motherboard out of the case and try to start the computer in the box the motherboard came in? All you really need to do to start the thing up is to plug in the power supply, put the CPU and heatsink and fan back on (don't forget to plug in the fan) and then temporarily short the power switch pins for a second or so and your computer should start up. If you try the box method you then eliminate the case as a potential short.

    Your computer isn't overheating, five seconds isn't enough time for your processor to overheat. And a working motherboard with a working brain (CPU) would give error codes, so I'm guessing that your motherboard is toast.
     
  3. madboyv1

    madboyv1 TechSpot Paladin Posts: 1,333   +267

    have you considered that there might be something wrong with the new PSU or that the CPU may have not survived the powersurge?

    edit: what cinders said. Another thing to check is that the motherboard grommets are properly connected to the case tray and grounded with those little plastic red washers.
     
  4. Technochicken

    Technochicken TechSpot Paladin Posts: 729

    I had a problem almost exacly like this a while ago, and it turned out my mobo was shot
     
  5. daveca5150

    daveca5150 TS Rookie Topic Starter

    Thanks for the help so far.

    Madboy, I don't have plastic washers for the grommets. Neither the case or motherboard came with them. I thought you wanted direct metal contact in order to ground to the metal case? BTW, I did take the motherboard out and tried to start it out of it's case with the same results. I'm leaning toward a bad motherboard. I hope I didn't cause it somehow.
     
  6. daveca5150

    daveca5150 TS Rookie Topic Starter

    ended up being the processor afterall. I exchanged the motherboard thinking I bought a dud. But I bought a processor so I wouldn't have to make a trip back if that's what it was. I hooked up the new motherboard and old processor and had the same result. Then I put in the new processor and it posted!

    Thanks for all the help.

    Cheers,
    Dave
     
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