Computer turns on for about half a second, then off.

I just built a new system today and whenever I hit the power button I get about one full rotation out of the CPU fan before the power cuts on me. Also, in order to repeat this i need to unplug the power supply until the green motherboard light fades. Upon plugging it back in and hitting the power button i get the same results. Ive tried known good ram and the power supply is known to be good, I just took it out of my main desktop. I built the system with just the Motherboard, processor + heatsink, ram, and power supply outside the case first and experienced these issues.

i3 2120 CPU
ASUS P8H67-M LX Motherboard
8 GB G.Skill ram (tried a combination of different sticks and ram slots, plus I tried a 2 gig stick of G.Skill from my main computer that I know works)
Antec Earthwatts 650watt powersupply

My guess is a bad motherboard, because honestly its that or the CPU I cant see it being anything else. Im building this as a server and would like to get it together as soon as possible, any ideas?

Thanks to anyone who responds.
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  1. Are you sure your RAM is pushed all the way in?

    TBH this sounds more like a RAM problem or a PSU problem than a Motherboard or CPU problem.

    I trust Antec so I would lean away from that.

    Do you perhaps have any parts laying around or borrowable from a different computer that you could try other than the ones you laid out above?

    I would try it with the 2 gig stick from your old computer (assuming its on your motherboard's QVL, I don't know since you didn't say part numbers) and make sure it is pushed in hard.

    It needs to be all the way in for it to work. A lot of people have similar problems if they don't seat it well enough in the slot.
  2. Could be a shortcircuit triggering the thermal fuse in the power supply. Try pulling everything out. Attach the power supply to the motherboard with the power switch and påower cables only. If it still does the same. Then try another powersupply. Then its either the motherboard or the powersupply.

    If it turns on and stays on, then put the components back in one by one and observe wether the problems return
  3. This is also what happens when you wire the MB power wrong. There should be 2 cables to the MB, the long 20/24 pin connector, and the other probably 8 pin connector near the CPU. Please make sure you have the right power cable going to the MB near the CPU. A 6 pin PCI-E cable WILL FIT, but it WILL cause the problem you are describing. If your power supply is modular, the 2 permanent wires coming off your power supply are not loikely to be the 2 for your MB. One is typically a 20/24 pin for the MB, and one is typically a PCI-E cable for a GPU.

  4. the right pins were in the right slots, I made sure of that. im going to do a little testing when I get home today, thank you for your responses
  5. its not the power supply. I used the one in my main desktop to test it. any ideas?
  6. Not sure if you've tried it, but check absolutely everything, I just bought a new power supply and didn't realize that the PCie connector had a much stiffer push to get it to lock in, hope that helps, but good luck if it doesn't
  7. I too have had this problem as well.. I am a tech and I can tell you I tried everything short of replacing the MB. After my extensive research I can only assume there is something array with the power switching on the MB. I can jump the PSU and it fires right up. I can offer a workaround but no real fix. I believe a fix means replacing the MB. The work around is simple. First unplug the power cable from the power supply or switch it to the off position. now make a jumper wire about an inch long bend it into a U shape and short pins 15 & 16 on the 24-pin plug. You will need to look for a pinout of the 24 pin plug and be sure you are jumping the correct pins.. or you may end up with a totally fried system. These should be a black ground wire and a green PS-ON wire. All plugs are connected as normal so you would be shorting the pins from the top of the plug. Be sure you have a good connection with the jumper wire as this will just remain there. Now plug in the power supply or switch to the on position it may fire up on its own at this point or you may still have to press the case power button.... but it should fire up and start running. The drawback is now that the MB switching has been bypassed Windows can no longer shut off the computer correctly and also the case power switch will no longer function as intended and the only way to turn off the computer is to switch off the power supply or unplug it. Not a real healthy thing for the OS. :) My solution for this.. just leave it running 24-7 (chuckle) Hope this helps.. and good luck.
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