Computer will not boot, turns off

I've had this computer since October, I got it off eBay. Quad core tower, just what I needed. I've had no problems with it until Saturday when I came to switch it on.

It would turn on then turn off and back on again. I've tried seeing if it's the RAM (it's not), the HDD and CD Rom are fine too. All fans are spinning, so I'm confused as to what the problem is. Any ideas?

Comments

  • StigStig Posts: 12,446
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    Does it turn off even when 'cold' or only when it's been on a while? You need to eliminate overheating issues.

    Is it a custom made PC, or a branded model?
  • curiousclivecuriousclive Posts: 378
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    Also check the fins of the cooler have not become clogged up with fluff.
    May need to check the thermal paste on CPU and replace if previous owner did not apply it correctly. This will make computer switch off very quickly if some of the cores get hot.
  • Si_CreweSi_Crewe Posts: 40,202
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    When you say "it turns on then off again" can you be more specific?

    Do you get a BIOS message, does the POST run, do you even get a "beep" at power-up?

    If you don't get any signs of intelligent life at all (as above) then it's almost certainly hardware related or, at worst, a corrupt BIOS.

    If you DO get the POST but then it shuts down again it could be, erm, software or hardware.

    My PC recently did something similar, whereby it'd start up, POST and then shut down again after a few seconds.

    After an hour or so thinking the worst, I discovered my BIOS seemed to have thrown a wobbly and swapped around the boot order so the PC was starting up, waiting for a USB device to boot from and then, when it didn't find one, shutting down again.

    Reset the BIOS so it was booting from the system HDD again, stuck a new CR2032 in the mobo' (just to be on the safe side) and I've had no more problems since.
    Probably jinxed myself by writing this though. :o
  • [Deleted User][Deleted User] Posts: 7,341
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    I'd start looking for a new one if I were you.
    I was going to replace my previous one next year byt the monitor became unusuable.
  • MigsterMigster Posts: 4,204
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    I had a similar problem recently (well I say "similar", but you don't go into detail so perhaps not) with my PC starting and stopping after a couple of seconds with no POST screen. Having tried pretty much everything mentioned on here already, I removed the CMOS battery for 10 seconds and it booted up OK after that (I'm assuming this reset the BIOS to defaults which fixed whatever the problem was).
  • BluedabadeeBluedabadee Posts: 589
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    The computer does not beep, as soon as I switch the machine on it just turns off again. The fans aren't clogged up either, I don't get any BIOS screen, no beeps - nothing.
  • Si_CreweSi_Crewe Posts: 40,202
    Forum Member
    The computer does not beep, as soon as I switch the machine on it just turns off again. The fans aren't clogged up either, I don't get any BIOS screen, no beeps - nothing.

    In that case, I'd say the PSU should be your first avenue of investigation.

    Remove the PSU from the computer, start it up like THIS and then use a multimeter to test all the supply voltages etc.
  • MigsterMigster Posts: 4,204
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    The computer does not beep, as soon as I switch the machine on it just turns off again. The fans aren't clogged up either, I don't get any BIOS screen, no beeps - nothing.
    This does sound the same as my problem, so worth trying the CMOS battery as I posted previously.
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