820-00138-A no power

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  • r0ck3tman
    New Member
    • Jul 2020
    • 3
    • USA
    #1

    820-00138-A no power

    This is my first repair so please be patient with me.
    I get green then orange light at the magsafe.
    Fans are not coming on.
    This is what I have checked

    PPBUS_G3H 12.54v
    PPDCIN_G3H_ISOL 16.66v
    PPVRTC_G3H 3.37v
    PP3V3_S5 0.42v

    U1900
    pin 1 PPVRTC_G3H 3.37v
    pin 2 PP3V3_S5 0.42 - C1902 0.42v
    pin 5 PP3V3_S5 0.42
    PP5V_S4RS3 missing
    PP3V3_S4 missing

    U7100
    pin 11 SMBUS_SMC_G3_SCL 3.3v
    pin 19 PP5V1_CHGR_VDD 5.47v
    pin 12 PP3v42_G3H 3.37v



    U7501 pin 12 SMC_PM_G2_EN 3.13v
    U7501 pin 14 PP5V_S5 4.80v
    U7501 pin 29 PP5V_S5 4.80v
    C7505 pin 1 PP5V_S5 4.80v
    U7501 pin 4 P5VS4_EN is 0.93v
    R8175 pin 2 P5VS4_EN is 0.93v
    C8174 pin 1 P5VS4_EN is 0.93v
    R8174 pin 2 P5vS4_EN is 0.93v
    U7501 pin 21 P3V3S5_EN is 2.9v
    U7501 pin 32 P5VS4_LL is 0v This could be incorrect.
    C7524 pin 2 P5S4_LL is 0v


    The only area where there is possible corrosion is at C7524 and pin 32 of U7501

    SMC_ONOFF_L is 3.4v and shorting it does not turn on the fans.

    My first thought is U7501 is bad and needs to be replace. I have not done so yet. I also thought of replacing C7524

    Please let me know if I'm missing anything and if I need to check something else.
    Tags: None
    • piernov
      Super Moderator
      • Jan 2016
      • 4435
      • France
      #2
      Re: 820-00138-A no power

      First thing you should confirm the batteries in your multimeter are good and that the multimeter is not too out of calibration. A good part of the measurements you report are out of tolerance.

      Originally posted by r0ck3tman
      PP3V3_S5 0.42v
      U7501 pin 21 P3V3S5_EN is 2.9v
      The only area where there is possible corrosion is at C7524 and pin 32 of U7501
      My first thought is U7501 is bad and needs to be replace. I have not done so yet. I also thought of replacing C7524
      Well, you found the problem, time to get down to work. While you're at it you should check for a short to ground on PP3V3_S5.
      OpenBoardView — https://github.com/OpenBoardView/OpenBoardView

        Comment

        • r0ck3tman
          New Member
          • Jul 2020
          • 3
          • USA
          #3
          Re: 820-00138-A no power

          Thanks Piernov.
          As I'm new to this, what is the best way to check that? Set the multimeter in Diode Mode with red to ground with power off? or is there some other way?

            Comment

            • piernov
              Super Moderator
              • Jan 2016
              • 4435
              • France
              #4
              Re: 820-00138-A no power

              I use resistance mode rather than diode mode but doesn't really matter here.
              OpenBoardView — https://github.com/OpenBoardView/OpenBoardView

                Comment

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