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Strange PSU behavior

So here's the deal, I unplug everything on the PC, bring it in the kitchen install a new fan, replug it and the following happens each time the computer is ''unplugged''.

I press the power on switch, comp seems to boot up (you hear the fans the power led lights up etc) but then it shuts down. It stays down for 5 seconds then it starts back up and the computer boots no problem.

I tested it with only unplugging the PSU without moving the pc and it did the same thing.

I give the PSU 2-3 minutes to fill up it's capacitors too before pressing the power switch, but waiting up to 10 minutes (tried it once) does nothing.

It only recently started to do this too... I had this PC for 2 years and a half and dusted it each month and never had this happen until recently.
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  1. Hi.

    What are the rig's components? Can you test with another PSU?
  2. MB: Asus P5Q (regular one) MCH=P45

    CPU: Core 2 quad Q9400 (overclocked to 3.6Ghz 2.66ghz original clock) (max temp under load 57C) Stable

    GPU: Asus EAH4870 512M memory (ati radeon hd 4870) not overclocked

    HDD: 1 Green WD 1TB and 1 Green WD 2TB

    PSU: Corsair TX750W

    Case: Collermaster CM690

    RAM: 2x 2GB DDR2 800MHZ kingston Overclocked to 903MHZ (451FSB)

    Windows 7 professional 64 bit (kinda meaningless since it all happens before windows attempts to load though)

    I don't have a spare PSU with me unfortunately... I'd have to buy one to test lol.

    On another note, my brother's rig is almost identical to mine (he isn't overclocked, has 1 hard drive and windows XP) and his PSU just failed recently so he has to replace it lol.

    Have to say I took care of mine alot more than he did, his computer was incredibly dust clogged.
  3. Down clock your RAM and try again.
  4. I took down my overclock from 3.6 to 3.2 which reduced Ram speed to 800MHZ. Ram wasn't overclocked but the problem presisted.

    I then loaded setup defaults in bios and changed stuff like boot priority and turned off Floppy drive and the problem went away??

    I can only conclude that it's the MB's bios that behaves strangely with certain settings. I'd have to mess around with them 1 by 1 to determine which one does it.

    Do you think I should try to correct the problem? Can starting, shutting down and restarting damage my PC's components? (it would happen a couple of times a month (4-5 max))

    I was afraid that it meant that my PSU was failing, but I ran OCCT power supply test (loads CPU and GPU to 100%) for 30min no problem so it can't be that it has a hard time handling the load that booting up demands.

    Thanks for your help so far, I didn't think that it was linked to my overclocking at all.
  5. or a short between mobo and case.
  6. Since my computer works perfectly except from that it can't be that there's a short somewhere right? And the MB is shorted to the case by the 6 screws (for the GND) but if something else was shorted by some way the consequences would be a lot more dramatic right?

    I might have misunderstood your answer though (I'm kinda paranoid lol).

    I'll be away for something like 4 hours and won't be able to answer or read posts until then.
  7. Best answer
    Nevermind, it's not a short.

    You have a good PSU, but if you can test with another PSU.
  8. If I can put my hand on one I'll try it, thanks for your help.
  9. Best answer selected by thyrokio.
  10. thyrokio said:
    So here's the deal, I unplug everything on the PC, bring it in the kitchen install a new fan, replug it and the following happens each time the computer is ''unplugged''. I press the power on switch, comp seems to boot up (you hear the fans the power led lights up etc) but then it shuts down. It stays down for 5 seconds then it starts back up and the computer boots no problem.

    I tested it with only unplugging the PSU without moving the pc and it did the same thing.

    I give the PSU 2-3 minutes to fill up it's capacitors too before pressing the power switch, but waiting up to 10 minutes (tried it once) does nothing.

    It only recently started to do this too... I had this PC for 2 years and a half and dusted it each month and never had this happen until recently.

    http://en.wikipedia.org/wiki/Fake_boot
  11. Ooooh! this explains it then lol. Thanks alot.
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