A1990 820-01041-A no video

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  • pascable
    Member
    • Feb 2018
    • 28
    • France

    #1

    A1990 820-01041-A no video

    Hello everyone

    First of all, thank you for your kindness, I do not speak English and I am using Google Translate to write my message to you.
    Hope you will understand me and can help me.
    Logic board 820-01041-A MacBook A1990.
    It starts up without problem, boots very well on an external screen but no video display on the MacBook screen, no backlighting.
    I am not a great specialist in electronics but I noticed that at pins 43 (0V), 44 (0V), 45 (0V) and 46 (5.5V), of the J8500.
    Is this normal because of another line?
    If you can guide me what to check, thank you very much.

    Sincerely, Pascal (France - Reims)
  • mon2
    Badcaps Legend
    • Dec 2019
    • 13836
    • Canada

    #2
    Re: A1990 820-01041-A no video

    hello.

    What is the history of this computer? Any liquid damage ? Look for red dots on the logic board which indicate that liquid was spilled.

    No display even if you use a flashlight on the front of the screen ? Can you see the apple logo with the flashlight?

    Comment

    • pascable
      Member
      • Feb 2018
      • 28
      • France

      #3
      Re: A1990 820-01041-A no video

      No trace but liquid received.
      Pa sde backlight, I watched with a lamp.

      Comment

      • pascable
        Member
        • Feb 2018
        • 28
        • France

        #4
        Re: A1990 820-01041-A no video

        Could the fault come from a line other than:
        PP3V3_S0SW_LCD (44)
        PP5V_S0_ALSCAM_F (46)
        PP5V_S0SW_LCD (45)
        These are the pin numbers of the J8500.

        Comment

        • mon2
          Badcaps Legend
          • Dec 2019
          • 13836
          • Canada

          #5
          Re: A1990 820-01041-A no video

          check the attached and post your values.

          added another check point - check the rail BEFORE the current sense resistor.

          where was the liquid damage ? has it been repaired?
          Attached Files
          Last edited by mon2; 04-29-2021, 09:34 AM.

          Comment

          • pascable
            Member
            • Feb 2018
            • 28
            • France

            #6
            Re: A1990 820-01041-A no video

            For 1 on C8509 (U8500) = 0V
            For 2 on C8510 (U8501) = 3.3V
            For 3 on R8520 pin 2 = 0V
            For 3 on U8510 1 = 3.38V
            For 4 on U8501 2 = 3.38V

            Comment

            • mon2
              Badcaps Legend
              • Dec 2019
              • 13836
              • Canada

              #7
              Re: A1990 820-01041-A no video

              Please confirm that your results are:

              For 1 on C8509 (U8500) = 0V
              For 2 on C8510 (U8501) = 3.3V
              For 3 on R8520 pin 2 = 0V
              For 4 on U8510 1 = 3.38V
              For 5 on U8501 2 = 3.38V ; is this the reading on pin 5 of U8501 ?

              Comment

              • pascable
                Member
                • Feb 2018
                • 28
                • France

                #8
                Re: A1990 820-01041-A no video

                I watch this in the morning and first of all, thanks for your help.
                See you later.

                Comment

                • pascable
                  Member
                  • Feb 2018
                  • 28
                  • France

                  #9
                  Re: A1990 820-01041-A no video

                  On my board there is an error. Pin 5 is denoted 6. It goes to pin 1 of the R8520 and it has 0V.
                  C8509 = 0V (no short circuit to GND)
                  C8510 = 3.38V + 3.38V on the 3 and 1 of the U8501
                  R8520 (without component, just solder point):
                  On the 1 = 0V
                  On the 2 = 0V
                  On the 3 = 0.2V not stable
                  On the 4 = 0.1V not stable
                  U8510 on pin 1 = 3.38V
                  U8501 on pin 5 (noted 6 on the boardview) = 0V

                  Comment

                  • sherifbekhit
                    Member
                    • Feb 2017
                    • 19
                    • alex

                    #10
                    Re: A1990 820-01041-A no video

                    Hi friends
                    I cant found spi flsh chip
                    Any body can help me plz.

                    Comment

                    • pascable
                      Member
                      • Feb 2018
                      • 28
                      • France

                      #11
                      Re: A1990 820-01041-A no video

                      What is "flsh spi chip"?
                      Apple reference please and I will help you.

                      Comment

                      • wws911
                        Member
                        • Apr 2020
                        • 10
                        • South Africa

                        #12
                        Re: A1990 820-01041-A no video

                        Hey have same kind of issues. Apparently liquid damage.. we're do I check

                        Comment

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