Imac 21.5 lcd issue

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  • jasko_jacker
    Badcaps Legend
    • Oct 2014
    • 1137
    • italy

    #1

    Imac 21.5 lcd issue

    When I push the power button I hear the sound but the screen remain black,
    only after a few attempts , the screen turns on.
    (The HD seems to work even when the screen remains black, and when the lcd is on the pc work well for many hours)
    I noticed that on the card that manages the voltage for the lamps (darfon 4h + v2676.081) there is a connector with this signal:
    pin 4 GND
    pin 3 ENABLE
    pin 2 DIM
    pin 1 VSYNC
    Enable signal is missing when the screen is Black and have 1.6V
    when the screen is on.
    I have no schematic and I don't understand well this type of hardware and I want to know if the enable is an OUT or IN signal ?
  • piernov
    Super Moderator
    • Jan 2016
    • 4435
    • France

    #2
    Re: Imac 21.5 lcd issue

    Would be nice to know what machine it is…
    OpenBoardView — https://github.com/OpenBoardView/OpenBoardView

    Comment

    • rediii
      h???, spurrrn
      • Mar 2018
      • 485
      • somewhere in europe

      #3
      Re: Imac 21.5 lcd issue

      gpu intact?

      Comment

      • jasko_jacker
        Badcaps Legend
        • Oct 2014
        • 1137
        • italy

        #4
        Re: Imac 21.5 lcd issue

        Originally posted by piernov
        Would be nice to know what machine it is…
        Label is missing but I think the model is Apple iMac 21.5 A1311
        The pic is a similar inverter board
        I post original pic as soon as possible
        Attached Files
        Last edited by jasko_jacker; 10-28-2019, 04:10 PM.

        Comment

        • jasko_jacker
          Badcaps Legend
          • Oct 2014
          • 1137
          • italy

          #5
          Re: Imac 21.5 lcd issue

          Originally posted by rediii
          gpu intact?
          I do not know it personally, but the owner who uses it with windows instead of macos told me that the video card is recognized.

          Comment

          • piernov
            Super Moderator
            • Jan 2016
            • 4435
            • France

            #6
            Re: Imac 21.5 lcd issue

            There are 4 different models of A1311, only one doesn't have a dedicated graphics card. That's 3 chances out of 4 to have a dead GPU.
            OpenBoardView — https://github.com/OpenBoardView/OpenBoardView

            Comment

            • jasko_jacker
              Badcaps Legend
              • Oct 2014
              • 1137
              • italy

              #7
              Re: Imac 21.5 lcd issue

              I have Only this info without dismantling motherboard, but I see the screws of a videocard rear heatsink.
              Can I try a reflow or this type of bga is in the "black list" ?
              Attached Files
              Last edited by jasko_jacker; 10-28-2019, 04:21 PM.

              Comment

              • KvnTM
                Badcaps Veteran
                • May 2018
                • 434
                • Germany

                #8
                Re: Imac 21.5 lcd issue

                It is this one:


                NVIDIA GeForce 9400M graphics with 256 MB of shared memory or ATI Radeon HD 4670 graphics with 256 MB of dedicated GDDR3 memory.
                Both of them are known to fail. Throw it away and avoid pre 2012 Mac's at all cost.
                Last edited by KvnTM; 10-29-2019, 04:38 AM.

                Comment

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