MacBook pro A2289 with touchbar stuck at 5V, 0.43A

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  • Zilicon
    Senior Member
    • Nov 2020
    • 141
    • Nigeria

    #1

    MacBook pro A2289 with touchbar stuck at 5V, 0.43A

    Greetings everyone.
    I've been trying to resolve the above problem, I need insight into the next step to take. This will be my first time handling this kind of machine hence, any replacement part will need to be ordered for since I do not have replacement parts.

    readings on the MB:
    PPBUS_G3H is present (12.23v)
    PP3V3_G3H is present (3.27v)
    PP1V8_SLPS2R is present (1.7v)

    The C-ports behavior:

    The port that communicated with U3200 delivered the above readings although the u3900, u3100, u3200 regions warmed up.

    However, the port that communicated with the u3100 delivered different readings- PPBUS was 1.7V, PP3V3 is 0. but the voltage at the USB meter still reads 5V, 0.43A

    I found out PP3V3_UPC_XA_LDO on U3100 read 26ohms to ground, it remains the same after I removed C3108. While PP3V3_UPC_XB_LDO on U3200 read 1.3k to ground. But the voltage reading at u3200 is 3.3V while at u3100 is 2.3V

    I'm stuck at which step to take next:
    Do I replace the U2890 or U3100 or attempt DFU mode so as to reprogram the T2 security chip, or should I remove the U4770 and reprogram it?

    I have a EZP2019 programmer, I think it should be able to read and write on the U4770 chip, but I couldn't lay my hands on the firmware yet.

    Please, what would you advise?

    Thanks


    background information on the PC:

    The charger was shaky, it indicated charging not charging, an attempt was made to adjust the charger perhaps it would stabilize, but a sparking sound was heard. the PC was unplugged, but the charging notification was still on despite the fact that the PC had been unplugged.

    Owner said the battery was not charging at all, it decreases even when the PC is plugged in, but the notification says the PC was charging. He attempted PRAM/SMC reset but the PC died afterward
    Last edited by Zilicon; 09-13-2023, 01:35 AM.
  • mon2
    Badcaps Legend
    • Dec 2019
    • 13850
    • Canada

    #2
    Re: MacBook pro A2289 with touchbar stuck at 5V, 0.43A

    Is the current draw from the type C port static at 0.43A or a variable and peaks to this value?

    The ISL device is a buck-boost regulator.

    The default power delivery contract is 5V. With this voltage as an input, the ISL will act as a boost regulator to output the ppbus_g3h rail.

    When the cd3217 devices are working correctly, the power delivery will bump to 20v as the input. Then the ISL will enter buck regulator mode to offer a lower output voltage with the higher input voltage.

    The difference being that in boost mode, the regulator current is always lower than when in buck regulator mode.

    The low resistance on the LDO rail is of concern.

    Comment

    • Zilicon
      Senior Member
      • Nov 2020
      • 141
      • Nigeria

      #3
      Re: MacBook pro A2289 with touchbar stuck at 5V, 0.43A

      Yes, it is constant.

      the port that doesn't produce PPBUS reads: 5V 0.17A
      while the PPBUS is 0.7v

      the PPBUS of the working port is 12.18v

      Comment

      • mon2
        Badcaps Legend
        • Dec 2019
        • 13850
        • Canada

        #4
        Re: MacBook pro A2289 with touchbar stuck at 5V, 0.43A

        the PPBUS of the working port is 12.18v
        SMC has not kicked in to boost this to 12v6.

        Reference:
        https://logi.wiki/index.php?title=PPBus_G3H

        Is the power delivery type C meter reporting 5v or 20v from the external power adapter? It must be 20v if all is working properly with the CD3217 controllers.
        the port that doesn't produce PPBUS reads: 5V 0.17A
        while the PPBUS is 0.7v
        Review each of the LDO rail on this non-working port.

        Review the DIODE mode readings of the CCx lines which are used for the BMC communication with the external power delivery adapter. CC1 will be used on one side of the type C blade / CC2 on the other side.

        Remove all power -> meter in diode mode -> red meter probe to GROUND (yes red) -> black meter probe onto CCx pin to test. Compare these readings against the working / known good port(s).

        You may have to replace the CD3217 controller if it is not working.

        Comment

        • Zilicon
          Senior Member
          • Nov 2020
          • 141
          • Nigeria

          #5
          Re: MacBook pro A2289 with touchbar stuck at 5V, 0.43A

          Originally posted by mon2
          SMC has not kicked in to boost this to 12v6.

          Reference:
          https://logi.wiki/index.php?title=PPBus_G3H

          Is the power delivery type C meter reporting 5v or 20v from the external power adapter? It must be 20v if all is working properly with the CD3217 controllers.
          The type c meter reported 5v, 0.43A

          Comment

          • Zilicon
            Senior Member
            • Nov 2020
            • 141
            • Nigeria

            #6
            Re: MacBook pro A2289 with touchbar stuck at 5V, 0.43A

            Originally posted by mon2
            SMC has not kicked in to boost this to 12v6.

            Reference:
            https://logi.wiki/index.php?title=PPBus_G3H


            Review the DIODE mode readings of the CCx lines which are used for the BMC communication with the external power delivery adapter. CC1 will be used on one side of the type C blade / CC2 on the other side.

            Remove all power -> meter in diode mode -> red meter probe to GROUND (yes red) -> black meter probe onto CCx pin to test. Compare these readings against the working / known good port(s).


            You may have to replace the CD3217 controller if it is not working.
            The CCs read fine.

            XA_CC1 0.537
            CC2 0.534

            XB_CC1 0.539
            CC2 0.538

            I might have to replace U3100, especially since both C ports behave differently. wish me success

            Comment

            • mon2
              Badcaps Legend
              • Dec 2019
              • 13850
              • Canada

              #7
              Re: MacBook pro A2289 with touchbar stuck at 5V, 0.43A

              Review this:

              https://boards.rossmanngroup.com/thr...k-at-5v.63201/

              Comment

              • Zilicon
                Senior Member
                • Nov 2020
                • 141
                • Nigeria

                #8
                Re: MacBook pro A2289 with touchbar stuck at 5V, 0.43A

                Originally posted by mon2
                Alright.

                Thanks a lot, Mon2, I really appreciate your invaluable assistance

                Comment

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