PC turns on, then immediately off.

Hi, I recently built a new computer, but have experienced a problem when trying to turn it on: the PC immediately turns off.

My motherboard comes with a built in power switch (with an LED) that glows when I connect and turn on the PSU,
however, when I click either the built in power button or the one on my case, the computer powers up for a second (The fans activate, and all the LEDs glow) but immediately shuts off.

Pressing the power button again has no affect, but If I hold it down or restart the PSU, I am able to turn the motherboard off and then back on. The problem however, repeats every time I do this. Also, when I connected the computer to a monitor, there's no video output.

I went through stickied checklist and nothing seems to apply to my situation. (I don't have a system speaker though, so I wasn't able to test for beep-codes.
So far I've tried re-inserting the CPU, applying thermal paste reconnecting everything, and testing with only the power supply connected, but nothing seems to be working.

Computer Specs:
Antec Twelve Hundred Black Steel ATX Full Tower Computer Case

Intel Core i7-930 Bloomfield 2.8GHz 4 x 256KB L2 Cache 8MB L3 Cache LGA 1366 130W Quad-Core Desktop Processor

CORSAIR DOMINATOR 6GB (3 x 2GB) 240-Pin DDR3 SDRAM DDR3 1600 (PC3 12800) Triple Channel Kit Desktop Memory Model TR3X6G1600C8D

ASRock X58 Extreme 3 LGA 1366 Intel X58 SATA 6Gb/s USB 3.0 ATX Intel Motherboard

NVIDIA Geforce 8500 GT (Temporary, will be replaced with an XFX Radeon HD 5850)

Western Digital Caviar Black WD6401AALS 640GB 7200 RPM 32MB Cache SATA 3.0Gb/s 3.5" Internal Hard Drive


XIGMATEK Intel Core i7 compatible Dark Knight-S1283V 120mm Long Life Bearing CPU Cooler

ASUS Black 24X DVD+R 8X DVD+RW 12X DVD+R DL 24X DVD-R 6X DVD-RW 12X DVD-RAM 16X DVD-ROM 48X CD-R 32X CD-RW 48X CD-ROM 2MB Cache SATA 24X DVD Burner - Bulk - OEM
4 answers Last reply
More about turns immediately
  1. something is grounded. remove the motherboard from the case and put it on a non conductive surface and try to turn it on.

    If that work, then something is wrong with your asembly. probably a misplaced standoff.
  2. I tested it again, with the motherboard on a wooden surface, but the same thing happened. CPU Fan and PSU turned on for a second, then immediately shut off.
  3. Sounds to me like one of two things.

    1: Incorrectly seated RAM (I have seen this cause what you describe, reboot cycles, etc.)

    2: Faulty power supply. If you have another of comparable wattage you could try it, or try that PSU in another computer.
  4. Your were right about the power supply. Plugged the MB into another one and everything seemed to have worked fine. Thanks!
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