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Thread: PC won't boot.

  1. #1
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    PC won't boot.

    Hi,

    I've had a couple of problems with my desktop over the weekend.

    Initially it would power up for about 5 seconds - I could hear the fans start but there were no beeps and then it would shut down.

    I googled the problem and initially thought it might be a problem with the power supply unit, CPU or motherboard.

    However, one suggestion was to remove the battery from the motherboard for a few minutes which would make the motherboard/bios (??) reset itself. I tried this and, after doing a system repair on Windows 7 with the installation disk, I managed to get it to boot up normally.

    I then shut it down, plugged everything back into the PC and put it back in it's desk and tried to start it up and it was as dead as a dodo !! No fans,no beeps, nothing.

    I've opened it up and there is a green light lit up on the motherboard, so I guess it must be getting some power, but I'm at a bit of a loss as to what has caused this.

    Am I back to square 1, with the problem being one of the PSU, CPU or mobo ?

    I must confess that I thought it might have been the power on switch and in my enthusiam to get at it, I've managed to pull the wires off it and can't get them back on, so I've ordered a new switch today. D'oh.

    Any help/suggestions would be appreciated.

    Thanks
    Steve

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    Hello Steve, welcome.

    Whatever the initial problem was, it seems to have escalated or developed a new problem. I think you need to address the symptoms as presented right now:.....

    .....start it up and it was as dead as a dodo !! No fans,no beeps, nothing.
    Before getting your hands too dirty so to speak, try a simple check: disconnect all USB connections to the box and try re-boot - some usb devices can lockup the BIOS if not configured correctly. If it boots without any USB devices, connect one by one until it fails to boot and take it from there.

    If it fails to boot with all USB devices disconnected it's back to basics. Disconnect all peripheral connectors - hard drive, CD/DVD, gfx cards, RAM etc. Leave only the PSU, motherboard and CPU. Take out the battery backup for the BIOS too. Now attempt to boot.

    If it does not boot with that minimal combination you have whittled it down to CPU (unlikely), Motherboard (possible), Power Supply (most likely of the three). Try obtain a spare known good psu and swap out, then repeat above, or use a power supply tester to check it out.

    If it does boot without the peripherals, it will likely generate a RAM warning error or a BIOS failure error (due to no battery backup) - possibly with a codified beep sequence dependent on your bios. Should this be the case, swap back in the battery backup and repeat the boot sequence. Continue this process swapping in one peripheral at a time (swap back in the RAM next) , until you find it doesn't boot. If that process is successful, you are a long way to identifying the faulty component.

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    Modern mobos remain powered on all the time, the green light, and fire up the CPU and peripherals when you push the power button - a simple push = on switch.
    If the power switch dies you will not be able to turn the extra power on and fire up the PC.
    If the mobo dies the power supply should still power on the peripherals, disks etc, unless the mobo / CPU dies and shorts out the power. Then you should not have the green light.
    If it's a disk etc the mobo should try to run but fail as the disk causes the power supply to shut down.

    cheers, Paul

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    Silver Lounger Banyarola's Avatar
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    I had a similar problem and it turned out to be a bad video card..

    Also, when resetting the BIOS by removing the battery you must have the PC UN-PLUGGED first
    "If You Are Reading This In English, Thank A VET"

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    Hi,

    Thanks for your replies.

    With the help of my Dad, who has got a electrical 'gizmo' which will read if there is an electrical current running through things, I think I've narrowed it down to either the PSU or motherboard.

    There is enough power to light up the green bulb on the mobo, but there appears to be no electrical current coming out of the leads from the PSU.

    My Dad and myself think there are 2 possible scenarios:

    1) The PSU is knackered, although where the mains lead plugs into the PSU there is some power going immediately into the PSU, but not to the leads that plug into the mobo, graphics card etc.

    2) My Dad thinks that there is a possibility that this indicates that there is a problem with the motherboard, as the PSU maybe expecting a signal from the mobo to switch the power on.

    Can anybody help with this ?

    Thanks
    Steve

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    Super Moderator CLiNT's Avatar
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    Repeat your BIOS reset as before, but this time...
    You might want to lighten the load of the PSU by unplugging the hard disk drive or disks (plural), all but one stick of RAM, and the CD/DVD player along with any other device not essential for a simple BIOS access.
    See if you are able to access BIOS. If you are then it's less likely to be the mainboard. It might not rule out a mainboard failure but it may point you in the right direction. You'd have a bit more to work with. The next step would be to test with a replaced PSU.

    Ensure that you have on/off functionality. It would be a plus if the mainboard had a reset or on/off button built onto the board.
    You may short the on/off or reset wires on the mainboards front panel connector, but be carfull and take electrostatic precautions.
    Last edited by CLiNT; 2011-10-09 at 11:00.

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    The switch on signal is shown on this Wikipedia page - pin 16. Check that this line is pulled to ground when you press the power on switch.

    cheers, Paul

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    Hi,

    Thanks for your replies.

    I'm still struggling a bit. I disconnected almost everything from the motherboard - graphics card, both stick of ram, audio cardm wireless card etc, just left a couple of fans connected, but even they didn't start up when I tried to start it up and no post beeps.

    I've removed the battery from the motherboard for a couple of minutes and then replaced it and still no joy.

    I've also tried re-setting the jumper wires but that hasn't worked.

    I guess that narrows it down to a problem with the motherboard or psu ? The cheaper option is probably to replace the psu so I may try that first.

    Thanks
    Steve

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    5 Star Lounger chowur's Avatar
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    You haven't described what type of system you have,such as a Dell etc.So I would like to suggest you buy a power supply tester.Which you can get @ most geek sites.They are much cheaper than a new power supply.Just a suggestion.
    Problems cannot be solved by the same level of thinking that created them. -Albert Einsten

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    Super Moderator jwitalka's Avatar
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    I've seen this symptom when the 4 or 6 pin aux power connector wasn't plugged in.

    Jerry

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    Quote Originally Posted by bigmig View Post
    Hi,

    However, one suggestion was to remove the battery from the motherboard for a few minutes which would make the motherboard/bios (??) reset itself. I tried this and, after doing a system repair on Windows 7 with the installation disk, I managed to get it to boot up normally.

    Any help/suggestions would be appreciated.

    Thanks
    Steve
    You did a system repair with the installation disk. That means that you successfully booted from something other than the hard drive, which suggests that you may have a hard drive problem. See if you can come up with some more interesting bootable drives (with programs or games apart from the operating system), disconnect the internal hard drive, and see if the thing will boot and run. If you have a bootable flash drive, try that. If everything is fine, that narrows the problem to your hard drive, which in turn may be corrupted and may or may not be easily repairable, and at worst may need replacement. If you do try to perform repairs, be sure to do it from CD or other source and not the drive.

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