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mobo or power supply problem what do you think?

By starscream ยท 5 replies
Oct 21, 2005
  1. My computer just shut off by itself last week. And it would not power back up.
    I stripped down the computer to the bare essentials, one stick of ram, video card etc... Through trial and error I have noticed that the PC will power up again but only if the keyboard is not plugged in. When I try to attach the keyboard in the off position, I start to hear weird fizzing noises. Nevertheless with the keyboard in, it will not power up. Also noticed that the floppy has no power to it. I cleared the CMOS JUMPER as well but that did nothing. I have an AMI bios. I got 1 beep followed by 3(although there was a very slight pause between the 2nd and 3rd). I have checked out AMI's codes and everything seems to point to the mobo. Has anyone ever experienced this sort of problem before. Do you think my mobo is the problem or do you think it may very well be that the power supply is creating this problem? Any input would be greatly appreciated thx.
  2. kirock

    kirock TS Rookie Posts: 1,221

    Considering it's much easier to swap in a keyboard, I'd try that first. Are you getting video out? If BIOS is beeping this usually means it knows it can't write to the monitor, so it beeps fail codes instead. Although some BIOS will not complete POST past whatever fault they find, in your case the keyboard.(my guess).and therefore won't load video driver.

    If it's not keyboard, then it very well might be the mobo connection at the keyboard or something in the interface chips dealing with the kb. In that case it's new mobo required. But before I did that I would try the PSU, again relatively easy to remove/install new one. What kind of computer is this?
  3. Rik

    Rik Banned Posts: 3,814

    If you are getting a fizzing sound it could be a capacitor blown on either the mobo or the psu.
    Have a good look at them all to see if any are leaking or have domed up on the top.
    You can test the psu bu shorting the green wire to any of the blacks too see if it will fire up properly.

    I personally recon it is one of the capacitors, have seen it happen twice before, problem is, if one has blown, what caused it, and has anything else been damaged by it.
    1 mobo i fixed, was just the one cap gone, the other was binned as it had caused loads of damage elseware.
  4. starscream

    starscream TS Rookie Topic Starter

    First of all thx to "Kirock" and "rik" for your great help. Well I finally got my hands on a power supply yesterday. I put everything back together and the PC is up and running again. It was the PSU afterall and not the mobo. :)

    Since the capacitors were not leaking and were all in good shape, I was hoping it was just the psu causing this strange problem and it was. Once again thx for the great help.
  5. Rik

    Rik Banned Posts: 3,814

    Glad you pc is working again...
  6. kirock

    kirock TS Rookie Posts: 1,221

    "Excellent Smithers"! Good job, it is always a good idea to try the PSU first, much easier and less expense.

    Cheers. :)
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