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    Black screen in Windows after recap of motherboard.

    I have a computer with a socket 468 motherboard that I found in a dumpster a few years ago. The computer has always worked perfectly but close to the processor I found two bulging caps that I decided to replace. The caps were 3300uF 6.3V Nichicon HM(M) and since there were four of them in total I decided to replace all four of them, despite only two of them showing visible damage. I left all the other caps alone. There was also some burn marks around the pin of the ATX socket where an orange (3.3V) and a brown lead goes. The original PSU was of really low quality (ACE Raw Deal 420W) and probably contributed to the damage.

    Anyway, I replaced the four Nichicon capacitors with Chemicon KZG of the same specifications. The new capacitors were unused, manufactured in 2007 and appeared genuine as far as the vent, bung and build quality goes. They measured a capacitance of about 3900uF (within 20% of their specified 3300uF) and an ESR of about 0.05. The crappy PSU was also replaced with a FSP PSU that had served me well before in another computer.

    The capacitors I replaced tested about 5500uF for the two without visible damage. One of the bulging ones were 4000uF and the other one was completely dead and not recogniced as a capacitor by the meter. The ESR of the first three was about 0.2-0.3.

    After the capacitor change was done I rebuilt the computer and fired it up. It works well until it loads the graphics driver of an operating system; then the screen goes blank and loses contact with the graphics card. I've tried both Windows XP and a Linux Live CD. Both DVI and VGA. Two different graphics cards (AGP by the way). Two different processors. A complete reinstall of Windows. The problem is always the same. If I start Windows with no graphics driver installed it will run on the generic drivers, but as soon as I install the dedicated Nvidia drivers the screen goes blank after the second "test flash" that occurs during the installation process.

    I tested the RAM with Memtest86+ and the processor with Prime95 and neither give any errors.

    Does anyone have any experienced this problem before and do you think it's related to the new capacitors or damage to the motherboard inflicted during the recap procedure?

    There are empty silkscreens for capacitors on the motherboard that seem to be connected in parallell to the capacitors I replaced. Could I improve stability by filling them with more capacitors?
    Last edited by Paddan1000; 12-28-2013, 06:16 AM. Reason: More information

    #2
    Re: Black screen in Windows after recap of motherboard.

    Where did you source the caps?
    The proliferation of bad and fake caps is immense!
    A genuine UCC cap should not be so far from the specs...

    Both Electrokit & Elfa in Sweden sell in small batches if you need it.
    And Topcat also offers international shipping nowdays...

    https://www.badcaps.net/store/
    http://www.electrokit.com
    http://www.elfa.se

    But are you sure the graphics card is ok, have you tried another one?
    "The one who says it cannot be done should never interrupt the one who is doing it."

    Comment


      #3
      Re: Black screen in Windows after recap of motherboard.

      Originally posted by Per Hansson View Post
      Where did you source the caps?
      The proliferation of bad and fake caps is immense!
      A genuine UCC cap should not be so far from the specs...

      Both Electrokit & Elfa in Sweden sell in small batches if you need it.
      And Topcat also offers international shipping nowdays...

      https://www.badcaps.net/store/
      http://www.electrokit.com
      http://www.elfa.se

      But are you sure the graphics card is ok, have you tried another one?
      I bought them from Ebay, but I inspected them carefully and they are industinguishable from the real ones. They even have that small "v" imprinted on the vent. Their only flaw was that they had short leads. The high capacitance could be that they had been in storage since they were manufactured in 2007 and had deteriorated somewhat. After all the KZG series is a known badcap despite being japanese. I'm just doing this for practice anyway and don't want to spend more money than I have to.

      The problem suddenly disappeared by itself. I reconnected the old Ace firetrap PSU and the computer started as normal. I thought the problem was the FSP PSU but then I reconnected it again and the computer still was fine. I had reconnected all the cables before, so I don't know why it solved the problem this time. Perhaps the hardware involved needed some burn in since it had been in storage for a while?

      Before the computer started working again I had soldered a 1500uF counterfeit chinese cap to one of the empty silk screens since that was the only one I had of a size that fit. I will leave it there as a test and see if it will fail before the other quality caps.

      The only problem left now is that the CPU is always at 100% because of the process svchost.exe, unless I kill that process. This might of course be related to something other than the capacitor change.
      Last edited by Paddan1000; 12-28-2013, 11:43 AM.

      Comment


        #4
        Re: Black screen in Windows after recap of motherboard.

        you need to turn off windows updates also do this through services as well seen this a lot lately.
        you can try this fix if you dont want to disable them of course
        http://www.infoworld.com/t/microsoft...2879017-230733
        Last edited by vinceroger69; 12-28-2013, 12:03 PM.

        Comment


          #5
          Re: Black screen in Windows after recap of motherboard.

          Originally posted by vinceroger69 View Post
          you need to turn off windows updates also do this through services as well seen this a lot lately.
          you can try this fix if you dont want to disable them of course
          http://www.infoworld.com/t/microsoft...2879017-230733
          Ok, thanks for the tip. If it's just a software issue I'm not too worried. The computer is updating now and if the problem doesn't go away after that I'll try the described fix.

          Comment


            #6
            Re: Black screen in Windows after recap of motherboard.

            Capacitors that have been in storage for a long time may need to be reformed, there is some info on it here in the forum if you search.
            But basically it comes down to that by applying a rising DC charge slowly they will rebuild the dialectic layer.

            Of course it will happen when you run the computer aswell, it's just that it might be too harsh and might make the capacitor fail instead.
            But if it's working now you can atleast assume it's probably better than it was before, not withstanding it being a KZG which might fail anyway
            They can fail with high capacitance btw, just like your boards original Nichicon HM did...
            "The one who says it cannot be done should never interrupt the one who is doing it."

            Comment


              #7
              Re: Black screen in Windows after recap of motherboard.

              Originally posted by Paddan1000 View Post
              I replaced the four Nichicon capacitors with Chemicon KZG of the same specifications.
              KZG, KZJ, TMV and TMZ are all defective UCC series with short lives, especially in extra hot conditions. KZG and KZJ like to fail without bloating.

              Rubycon MBZ or Nichicon HM (with a date code after 2005), would by my preferred replacement.

              Comment


                #8
                Re: Black screen in Windows after recap of motherboard.

                You measured capacitors with ? (make and model of instrument)...
                This behavior could be :
                - defective caps (were they used /short legs/ ? )
                - bad soldering (most likely, search forum how to solder CPU-vrm caps, hint high currents)
                - wrong PSU (ATX12 instead ATX 1.3, or vice versa )

                Comment


                  #9
                  Re: Black screen in Windows after recap of motherboard.

                  I have had the same issue. In my experience you sometimes need to have every hole filled. I always thought this was superstition, but now i have come to accept it. If you know the PCB well, then you will know what needs to be there and what does not, but often some areas are referenced by various processes, and there is no way of knowing.

                  Also, sometimes you can have problems channging PSUs or RAM together with other changes. If you simply make all other changes, then boot with old PSU, shut down, then re-boot with new PSU, it will work. |I cannot explain why. I have had similar issues with RAM that will not work (suck as my current Corsair Vengeance). Now the same RAM is overclocked and rock-solid stable.

                  Comment

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