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Dell P2212Hb - Black Display pattern

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    #1

    Dell P2212Hb - Black Display pattern

    Hello,

    I have a faulty Dell P2212Hb. It powers on fine with a constant blue light but it displays a weird mostly black pattern, and when I connect it to the computer it just displays black with what looks like backlight bleed around the edges. I've opened it up and taken some pictures of the 2 main boards and board that connects to the LCD. Does anyone have any idea what could be the issue?







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    #2
    Re: Dell P2212Hb - Black Display pattern

    I'm leaning towards T-con board issue, though it could also be bad caps letting too much ripple through and messing with the controller on the video/logic board. Or could also be a bad regulator on the video/logic board.

    The t-con board is the one you show in the last two pictures (attached to the LCD panel). Using a multimeter, check the DC voltage with respect to ground (monitor metal chassis) on test points VGH1 and VGL1. Report back what voltages you get. Should be about 15 to 35V for VGH1 and -5 to -10V for VGL1.

    Also, if you can, please post some pictures of the reverse side of the T-con. Be careful when you flip the T-con board to not rip any of the ribbons it is attached to.
    Last edited by momaka; 04-18-2016, 11:39 PM.

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      #3
      Re: Dell P2212Hb - Black Display pattern

      Originally posted by momaka View Post
      Also, if you can, please post some pictures of the reverse side of the T-con. Be careful when you flip the T-con board to not rip any of the ribbons it is attached to.
      ...And when you do please upload them here to the site instead.
      "The one who says it cannot be done should never interrupt the one who is doing it."

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        #4
        Re: Dell P2212Hb - Black Display pattern

        Sorry for taking so long but I finally got to testing those 2 voltage points. It's 28V for VGH1 and -10.21V for VGL1. Also these voltages were measured without any video output from a computer so the LCD might have been in standby mode while measuring. I don't know if that would make a difference.

        I've photos from behind that board this time too.
        Attached Files
        Last edited by funkster; 05-27-2016, 11:20 PM. Reason: Couldn't edit first post to reupload pictures as wanted so uploaded all here.

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          #5
          Re: Dell P2212Hb - Black Display pattern

          Originally posted by funkster View Post
          It's 28V for VGH1 and -10.21V for VGL1.
          Those seem good. It means that AVDD1 must also be present and okay. Can you confirm that, though, by measuring the voltage between test point AVDD1 and ground. I'm 99% sure it should be fine.

          Originally posted by funkster View Post
          Also these voltages were measured without any video output from a computer so the LCD might have been in standby mode while measuring.
          Monitor was probably ON and displaying the "No Signal" / "Check connection" message, otherwise VGH1 and VGL1 would be OFF.

          Anyways, since VGH1 and VGL1 are okay, I would suggest you replace the small electrolytic capacitors on the logic board. This one:
          https://www.badcaps.net/forum/attach...5&d=1464411865

          Speaking of which, what is that burn mark on the bottom right of the logic board?

          Also, while getting new caps for the logic board, you might as well get some caps for the power supply too, since you probably will be paying for shipping anyways. You don't need to replace the big high voltage cap, but replacing at least a few of the other caps in the power supply should be helpful (if you use good quality Japanese caps of course, like Panasonic, Rubycon, Nichicon, and United Chemicon... otherwise don't bother).

          That way, at least we will know the problem is not due to one (or more) faulty caps causing ripple to get to the video decoder/scaler chip and causing problems.
          Last edited by momaka; 05-29-2016, 07:35 PM.

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            #6
            Re: Dell P2212Hb - Black Display pattern

            Originally posted by momaka View Post
            Can you confirm that, though, by measuring the voltage between test point AVDD1 and ground. I'm 99% sure it should be fine.
            Volatge for AVDD1 to ground = 12.76V

            Originally posted by momaka View Post
            Speaking of which, what is that burn mark on the bottom right of the logic board?
            I looked a little close and it looks like the flux left over from when they would've soldered the white header that connects to the usb ports on the side panel. I scraped some off with my fingernail as you can see in the close up photo that I've attached, and there doesn't seem to be any damage underneath, so no burn mark.

            I'll look for some capacitor replacements in the meantime, thanks for that momaka.
            Attached Files
            Last edited by funkster; 05-30-2016, 12:59 AM.

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              #7
              Re: Dell P2212Hb - Black Display pattern

              Originally posted by funkster View Post
              Volatge for AVDD1 to ground = 12.76V
              Good. Within normal range as I expected.

              Originally posted by funkster View Post
              I'll look for some capacitor replacements in the meantime, thanks for that momaka.
              Okay.
              Let us know if you need help finding replacements.

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                #8
                If you want to try the working bios without any problems
                Attached Files

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