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bad caps or not on fried P4VMM2?

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    bad caps or not on fried P4VMM2?

    I should preface this by saying that the issue has been resolved and it's really only of academic interest of this point, I'm just curious as to whether my problem was caused by bad caps, or something else. If the capacitors are the problem, I can post photos and capacitor brand names.

    The motherboard is (was) an ECS P4VMM2. It had been working fine in a heavily-used desktop PC for almost 3 years. I'm not sure of the brand of power supply I used but I can check in a few days.

    Things started getting a little funny when I could hear the CPU working (actually it may not have been the CPU but definately not the hard drive or anything else normally audible): scrolling a webpage or whatever would make a sort of high-pitched hissing sound. This got worse over a couple weeks until there was an audible whine accompanying it, but I didn't think it was a problem. Then one day, halfway through loading Windows the computer shuts off completely. Prior to this there had been no crashes or errors, everything was totally stable. I restart it and it shuts off within a few seconds. So I open it up and some of the capacitors are visibly bloated and hot to the touch when it's turned on (but no electrolyte leakage). Even with everything disconnected it still shuts off- so I figure the motherboard is shot, maybe power supply too. While I'm reasonably skilled with electronics and probably could replace the capacitors, it's not that great of a motherboard so I'd rather just replace it.

    I take it to a computer store and tell them to replace the motherboard and test the power supply (not quite 1337 enough to do it myself). I get a call back saying that the motherboard tested fine but the power supply and hard drive are "bad". The hard drive was okay- it slaved in another computer without a problem (though possibly some Windows data got corrupted and it wouldn't boot- no way to tell at this point) and the motherboard isn't fixed- with the new power supply installed it doesn't shut off now but it still makes the same noise, worse than ever, and the capacitors still get very hot.

    So anyway after immense frustrations I backup the data, take it to less incompetant computer store that recognized the problem, and get it back with a new motherboard and wiped hard drive with a fresh Windows installation- everything's okay now.

    What I'm wondering, though, is what caused the problem. The capacitors were definately bad but did they fail on their own or was it caused by the power supply or something else? Consider the following:

    The motherboard worked fine for almost 3 years before failure.
    It failed by shutting off suddenly, which was "fixed" by replacing the power supply.
    There were no gradually worsening errors or crashes...
    But there *was* a gradually worsening high-pitched squeal (from what?).
    And the capacitors were hot to the touch- do capacitors with bad electrolyte die due to overheating?

    Like I said at the beginning, this doesn't really matter now, but I would like to know, just to appease my curiosity. Next time I'm home I can report back with the brand of power supply/capacitors and photos.
    Last edited by ac.r; 08-23-2005, 05:31 PM.

    #2
    Re: bad caps or not on fried P4VMM2?

    Yes, bad capacitors.

    --Randy

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      #3
      Re: bad caps or not on fried P4VMM2?

      Maybe check the CPU fan, too? The squealing may be that or the VRMs may be oscillating due to bad caps (the control loop has compensation for the ESR, and if it's way high, the loop couldoscillate).
      PeteS in CA

      Power Supplies should be boring: No loud noises, no bright flashes, and no bad smells.
      ****************************
      To kill personal responsibility, initiative or success, punish it by taxing it. To encourage irresponsibility, improvidence, dependence and failure, reward it by subsidizing it.
      ****************************

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        #4
        Re: bad caps or not on fried P4VMM2?

        Luxon or OST?
        Ya'll think us folk from the country's real funny-like, dontcha?

        The opinions expressed above do not represent those of BADCAPS.NET or any of their affiliates.

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          #5
          Re: bad caps or not on fried P4VMM2?

          It wasn't the CPU fan making the sound, I'm still using that on the new motherboard and it's fine. The more I think about it, it does seem like bad capacitors, I was just wondering because it doesn't seem like the typical mode of failure.

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            #6
            Re: bad caps or not on fried P4VMM2?

            Okay, just checked, the blown caps are all I.Q brand, the smaller capacitors (1500 uF or less) are G-LUXON but they're "okay", or at least haven't failed yet. I can post photos soon-ish.

            I looked in the power supply too, it's a SkyHawk SH300A8H. The capacitors are CapXon and Jun Fu (only a few smaller ones). Physically it seems okay but I'll assume it's bad because replacing it fixed the shut-off problem (though it may be that the newer one just supplies more current before the overload circuit kicks in). I'm not really going to try to test further because, like the motherboard, I'm not going to miss it anyway.
            Last edited by ac.r; 08-26-2005, 06:28 PM.

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              #7
              Re: bad caps or not on fried P4VMM2?

              Got photos, showing the bad OST I.Q capacitors as well as some of the "good" G-LUXON ones. They're not particularly exciting as none of the caps have leaked or vented, and actually they seem considerably less bloated than they were initially (hydrogen gas readsorbed?).





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