MBP 2015 A1398 820-00138 audio problem

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  • MicroSMD Lab
    Senior Member
    • Sep 2018
    • 139
    • Trinidad and Tobago
    #1

    MBP 2015 A1398 820-00138 audio problem

    Hello group, there is no sound from the internal speakers and it does not show up as a device, when I plug in a headphone, headphone does show up but all i hear is a recurring pop. The digital audio output gets activated.
    PP3V3_S0_AUDIO_ANALOG is 20ohm to gnd and PP4V6_AUDIO_ANALOG is 4.3ohm to gnd. Are these resistances ok, is voltage injection safe on these lines? Thanks in advance.
    Tags: None
    • mon2
      Badcaps Legend
      • Dec 2019
      • 14020
      • Canada
      #2
      Re: MBP 2015 A1398 820-00138 audio problem

      What are the voltage measurements of these power rails?

      They do sound (no pun) low to me. Do not do injection yet.

        Comment

        • MicroSMD Lab
          Senior Member
          • Sep 2018
          • 139
          • Trinidad and Tobago
          #3
          Re: MBP 2015 A1398 820-00138 audio problem

          PP3V3_S0_AUDIO_ANALOG is 3.3V and PP4V6_AUDIO_ANALOG is 1.7V
          4V5_REG_IN is 4.9V
          Last edited by MicroSMD Lab; 09-12-2022, 06:15 PM.

            Comment

            • mon2
              Badcaps Legend
              • Dec 2019
              • 14020
              • Canada
              #4
              Re: MBP 2015 A1398 820-00138 audio problem

              I don't have the schematics in front of me but locate all caps on this rail PP4V6_AUDIO_ANALOG.

              Start with the largest and carefully remove off the pcb or slide to one pad only. Then check the resistance of that rail again. Some part, likely a cap is shorted. The voltage should not be this low. Often the bad players are polarized tantalum capacitors.

                Comment

                • reformatt
                  Badcaps Legend
                  • Feb 2020
                  • 1401
                  • Australia
                  #5
                  Re: MBP 2015 A1398 820-00138 audio problem

                  U6200 (TPS71745) is only rated to 150ma max. 4 ohms will exceed that (V=IR). There are only 4 caps on this line and U6201 to isolate what is causing it.

                    Comment

                    • MicroSMD Lab
                      Senior Member
                      • Sep 2018
                      • 139
                      • Trinidad and Tobago
                      #6
                      Re: MBP 2015 A1398 820-00138 audio problem

                      Thanks for the responses mon2 and reformatt. I removed all 5 capacitors and U6200 but no change in resistance... removed the U6201 and short is gone
                      Last edited by MicroSMD Lab; 09-14-2022, 11:17 AM.

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