820-01987 pp3v3_s5 pulsing 20v 0.019A

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  • AJ847.63e
    Senior Member
    • Aug 2020
    • 166
    • Africa
    #1

    820-01987 pp3v3_s5 pulsing 20v 0.019A

    Hi all,

    Need some assistance with a 1987. History is its chassis was completely crushed trackpad and screen were shattered not sure how but it seems like it was ran over. Board visually seems fine doesn't look warped no visible cracks in anything board side.

    went through the power sequence diagram on logiwiki for the 01055 because there doesn't seem to be one for the 1987? All rails up until pp3v3s5 are present. Found out that pp3v3s5 and pp1v8s5 are coming on when you first connect the board but they shutdown after around 15 seconds or so.It seems like the PMIC is detecting a short on a minor sub rail and shutting down.

    so the question is are there any signature faults with the PMIC and the 820-01987? Unfortunately I do not have a thermal camera so I'm hoping there's a shortcut I can follow. Freaking seeks have gone from 500 to 900 hence why I've been putting it off, not to mention we don't do much of this so it's hard to justify spending a grand for a once in a blue moon job.

    thanks for the assistance!
    Tags: None
    • AJ847.63e
      Senior Member
      • Aug 2020
      • 166
      • Africa
      #2
      Re: 820-01987 pp3v3_s5 pulsing 20v 0.019A

      Great, looks like somethings burned out now the usb c meter is only giving 5V .2A. I went to check S3 & S0 rails, and they were also pulsing. Checked PP1v_s3 & PM_SLP_S0_L. Then went to check ALL_SYS_PWRGD and that's where the charger started outputting 5V 0.200A in all 4 orientations of the usb c cable.

        Comment

        • AJ847.63e
          Senior Member
          • Aug 2020
          • 166
          • Africa
          #3
          Re: 820-01987 pp3v3_s5 pulsing 20v 0.019A

          Should a fully updated A1708 be able to detect this board if I force it into DFU mode? repairwiki notes you must have a mac updated to the latest OS so I'm not sure if a A1708 should work as you obviously cannot install the latest OS on those.

          all sys pwr good is present for a split second than it shuts off. Traced it back and looks like the PMIC is shutting down hence why PP3v3_S5 and all following rails are coming up for a split second than disappearing. It looks like the T2 firmware is corrupted as both AWAKE and SLPS2R are present and stable so it seems like the T2 requires a DFU restore but I don't want to force it into DFU if I do not have a machine which will be able to detect it.

            Comment

            • AJ847.63e
              Senior Member
              • Aug 2020
              • 166
              • Africa
              #4
              Re: 820-01987 pp3v3_s5 pulsing 20v 0.019A

              Originally posted by AJ847.63e
              Great, looks like somethings burned out now the usb c meter is only giving 5V .2A. I went to check S3 & S0 rails, and they were also pulsing. Checked PP1v_s3 & PM_SLP_S0_L. Then went to check ALL_SYS_PWRGD and that's where the charger started outputting 5V 0.200A in all 4 orientations of the usb c cable.
              Disregard the above it was my USB C meter trolling me again. Switched sides on the USB C input cable a few times and now were back to 20V. Freaking china, why can't they make a single reliable device.!

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