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Built a computer, won't power on, need help

i built my first computer about a month ago, and everything worked fine on it for the first day. it ran for about 10 hours before i but it into sleep mode for the night. the next morning when i tried to turn it on, i got a half second of fan power, and then it died. after some troubleshooting i decided it was the power supply. the new computer has a 750 watt supply in it, but i thought i'd check the motherboard, so i plugged my old 650 watt supply into it just to see if the motherboard would power on by itself, which it did with no issues. i figured at that point the new power supply was the problem, so i rma'd it and got a replacement.

now we're to today. i finished hooking up the new power supply to everything, and i'm getting the exact same issue. the fans will spin for about half a second, but everything will die. is it just possible that i had really terrible luck with two power supplies, or is there something that i'm missing? when i tested before i unplugged my memory and it made no difference. this time around i unplugged each drive individually with still no difference. i have 4 case fans plugged into the supply as well.


sapphire pure platinum a75 (i won it. not purchased)
amd a8 3850
cooler master hyper 212 evo
2 x4gb corsair vengeance
seagate 1tb barracuda 7200rpm
lite-on dvd burner
corsair 750watt enthusiast series

i'm just using onboard video for the time. can anybody suggest what might be wrong? thanks for any advice
4 answers Last reply Best Answer
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  1. Here is our standard checklist for new builds that will not boot.
  2. Best answer
    Sounds like it could be shorting. Check to see if any metal parts are exposed to any plugs / connectors and see if that fixes it. I had this happen in a build and it was really subtle, you can't always see it but you can disconnect things to rule out faulty connections that could be causing the short.

    Try unplugging the PSU from everything except the CPU and Motherboard (and obviously the wall), and see if it boots and stays running. If it does, plug in to video next and keep plugging things into the PSU until it stops working.
  3. It is possible the problem is related to a power setting in the computer.

    Problems waking up from sleep mode after long periods of time that they have worked correctly usually signal a bad PSU.

    Problems waking up from sleep mode on a new PSU may signal the same thing or perhaps something else.

    My wife's computer has had a similar problem a few times and my own did it once recently too, I think maybe it was after an automatic windows update.

    It is just a suspicion I have, but both of our computers have the keyboard and mouse plugged into the monitor's USB ports. It may be an issue (with us at least) where the monitor enters into a strange power mode and since the USBs are plugged into it then they can't wake the computer up anymore.

    Every other day since I got my newest PSU, I had no problems of any kind.

    It just really feels like a menu setting somewhere to me (assuming the PSU is capable of powering the system and all that).
  4. Best answer selected by kahlandra.
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