PC won't boot

I've just build a new PC:

Gigabyte GA-P55M-UD2 Motherboard
Intel Core i5 760 CPU
ATI Radeon HD 5850 GPU

I really don't know what's gone wrong. After playing with the overclocking settings I had it running at 3.5GHz at a decent temperature for about 5-10 minutes after which all the power cuts out. No BSOD, no reset, just no power. I had had it higher earlier but was a little concerned about the heat so I opted for a lower overclock.

I tried to power the PC back up and nothing happens.

After turning off the power at the back of the PC for a little while then turning it back on again and attempting to power up, things started for a fraction of a second, some motherboard lights flashed on, fans twitched, then nothing again. Leaving it powered off for a few minutes made it repeat this process when I turned it on, attempting to turn it on again before then I didn't even get that brief power.

After trying various things without avail, I started unplugging things. Unplugging the 4x2 CPU power then attempting to power up the power came on for 2-3 seconds, then again cut out, it would continue to do this until I switched it off.

I'm using an OCZ 600W ModXstream PSU.

I've tried resetting the CMOS both via the jumper and by removing the battery for a few minutes, nothing helped.

Does this sound like a bad overclock / faulty PSU or something else?

Got any advice guys?

14 answers Last reply
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  1. unplug everything you can, gfx cards (unless you need that for monitor I.e no onboard gfx), hard drives opticals
    try booting with only the 20+4pin and the 2x4cpu power pin in,
    theres a breadboarding guide on here somewhere but I'm off out I'm afraid atm, i'll check back in a bit man,
  2. I've removed everything, tried booting with 1 stick of ram and no ram. Results were no different to when everything was plugged in.

    Can't get into the bios.
    The motherboard leds flash on but go off straight away.
    The system beeper is attached but it doesn't beep, doesn't stay powered long enough to get to the POST test.
    PSU fan doesn't move.
  3. Looks like psu issue to me at the moment, can you get aonther to check system's ok?
  4. I don't have another PSU with enough output to power my gfx card, My old PC is about 8 years old, its less than 300W output and won't have PCIe connections.

    Think it'll at least give me enough power for the POST test so I can see if power stays on?
  5. I was recommended on another forum to try shorting the PSU with a wire between the green and black wires to see if the PSU fan comes on, I did it and it does.

    Does this help diagnose what my problem is?
  6. Ok, You've jumped the 600w psu and its working?,
    Fill this in with your system specs and see what it says, I think your 300w box hasnt got enough for that 5850,but you may be able to at least get into bios, worth giving it a try I reckon
    see what you need and then maybe its shopping time for a new upgraded psu,
    I know a lot of people on here have had issues with Ocz psu's, you may just have a bad one, dont mention the overclocking to the rma people though imo
  7. The result from that site came out at 372W, I do have a 380W PSU as well in a HTPC.

    Its cutting it close but I might be able to get away with that as a temporary test.
  8. Hopefully it is putting out that 380 Watts but if thats what you have,
    try that psu in there, run the minimum you can to do it, as before on the breadboarding just to check if you can post/boot ok, I'll check back later when I get up :)
  9. Bare minimum breadboard: motherboard, CPU & HSF, PSU, and system speaker.

    When you try to boot, you should get a series of long single beeps indicating no memory present. Silence indicates that one of the 4 components are bad.

    A 5850 needs about 10 amps at 12 volts. Your 600 watt OCZ PSU, if working, should power it (and the rest of your system). The absolute bare minimum PSU I would use is a Corsair 450VX (33 amp 12 volt rail)

    What I would recommend is the Corsair 550VX (41 amp 12 volt rail)

    I don't like OCZ PSU's. Right now, I think they are marketing 4 different PSU lines. The newest line is supposed to be their attempt at a truly good PSU (the jury is still out). One is pretty good. The other two are barely OK. And I can't remember which ones are which.

    My memory is just not it used to be. Of course, at over 60, neither is anything else. :)
  10. Couldn't try the 380W PSU, It doesn't have the 2x4 CPU power connector, only a 2x2.

    With the OCZ PSU I don't get any thing with motherboard, CPU & HSF, PSU, and system speaker connected, if CPU power is connected it turn off instantly, without it connected it enters a cycle resetting every few seconds.

    Haven't had time to try the OCZ PSU in another PC yet.
  11. You should be able to use the 2x2pin from the 380W unit in there, just use the pins/sockets closest to the floor/desk when the Rig is stood upright,
    My Mobo's got an 8pin cpu socket but My psu only has a 4pin cpu line, works fine :)
  12. Okay, I might have a little progress here.

    I removed my CMOS battery again, left it for a couple of hours, only left it for about 5-10 minutes before.

    After putting it back in, nothing happened.

    Most of the power cables were still disconnected except for the Motherboard and CPU power, so I reconnected the other cables, don't know why, I wasn't expecting anything to happen.

    I switch it on and the power stays on for once and I get a continuous stream of shorts beeps, which according to the motherboard manual means "Power Error".

    There's no memory or graphics card in at the moment.
  13. Apparently the Power error was just because there was no memory, I put the memory in and the graphics card and everything's running okay now.

    I set all my overclock settings back to their defaults. Not sure if I'll try overclocking again.

    Thanks for your help guys. Appreciate it.
  14. Glad you got sorted in the end man,
    dont be put off clocking in future, just take it little bits at a time and learn as you go along :)
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