Macbook Air 13 2020 A2179 820-01958 partial power

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  • toinounet21
    Member
    • Jun 2023
    • 12
    • France
    #1

    Macbook Air 13 2020 A2179 820-01958 partial power

    Hi, glad to be back here after 3 busy years, today I'm working on this board (first T2, so forgive my stupid questions) board looks clean but maybe cleaned before

    Volt/Ampmeter says 5V -> 20V and steady 0.095A

    It seems power on, yesterday when I plugged charger I had the plugging sound and nothing on screen, I first thought about display problem, but I noticed that when I long press power button to force shut up, voltages that are not present when the board is turned off fall to 0 and rise up as soon as it tries to restart immediately.

    I tried to put it into DFU mode and restore firmware, it's OK but no changes (I haven't heard any sound since, but the voltages haven't changed)

    I tried to measure voltages indicated onhttps://logi.wiki/index.php/CD3217_and_T2_Power_on_Sequence and on this post https://www.badcaps.net/forum/showthread.php?t=103063

    all before power button is pressed are OK except maybe PPVDDCPU_AWAKE which is pretty low, 0.55V schematics indicates 0.625 - 1.06V, after all KO except PP3V3_S5 which is oscillating 3.15-3.25V PP5V_S5 is OK 5.1
    SMC_RST_L are low

    any idea to start or common fault?

    Thanks
    Tags: None
    • mon2
      Badcaps Legend
      • Dec 2019
      • 13866
      • Canada
      #2
      Re: Macbook Air 13 2020 A2179 820-01958 partial power

      Have the same design by the devil here.

      PP3V3_S5 - remove all power. Measure the resistance to ground of this rail. Also check if the enable for this rail is oscillating or not after the above check.

      BTW..do you need a battery to test this board? Have no screen, no keyboard and no battery so asking about your setup to help diagnose this board as well.

        Comment

        • toinounet21
          Member
          • Jun 2023
          • 12
          • France
          #3
          Re: Macbook Air 13 2020 A2179 820-01958 partial power

          not sure there is an _EN for PP3V3_S5 it seems to be generated by U7800, all others OK rails are steady, exactly same res as on the working board I have (130K)

          Just tested with this board, starts without battery/keyboard, CPU hot SMC_RST_L high of course

            Comment

            • toinounet21
              Member
              • Jun 2023
              • 12
              • France
              #4
              Re: Macbook Air 13 2020 A2179 820-01958 partial power

              I've noticed that PM_SLP_SUS_L is fluctuating less than 2V, and RES to GND is not 100K like on the working board but only 60K. I have replaced U7700, RES to GND is OK, now fluctuating up to 3.3V but always not steady (maybe bad soldered, 3 years I have not practiced )

                Comment

                • mon2
                  Badcaps Legend
                  • Dec 2019
                  • 13866
                  • Canada
                  #5
                  Re: Macbook Air 13 2020 A2179 820-01958 partial power

                  Carefully remove R7715 and see if the PM_SLP_SUS_L signal returns to a stable 3v3 level.
                  Attached Files

                    Comment

                    • toinounet21
                      Member
                      • Jun 2023
                      • 12
                      • France
                      #6
                      Re: Macbook Air 13 2020 A2179 820-01958 partial power

                      I tried with U7700 removed, I think it's even better, right? same oscillating value

                        Comment

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