820-00840 20v 0a

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  • powerblackout
    Senior Member
    • Feb 2018
    • 109
    • USA
    #1

    820-00840 20v 0a

    suddenly stopped turning on. no corrosion at all board seems in great shape. ammeter sits at 20V 0A.

    PPBUS_G3H - 13.0V
    PP5V_S5 - 4.99V
    PP3V3_S5 - 3.3V
    PP5V_S4 - 0V no shorts

    SMC_PM_G2_EN - 3.4V
    PP3V1_RTC - 3.1V
    PM_DSW_PWRGD - 3.4V

    PCH_INTRUDER_L - 2.84V
    PCH_SRTCRST_L - 3.1V
    PPDCPRTC_PCH - 1.14V

    PM_SLP_S5_L - 0V
    PM_SLP_S4_L - 0V


    Any ideas on where to start? This seems like the PCH is dead or not getting power?

    more measurements:
    PM_EN_P3V3S5G - 3.3V
    PP3V3_S5G - 0V with 0.7ohm short to ground
    Last edited by powerblackout; 03-18-2022, 09:47 PM.
    Tags: None
    • mon2
      Badcaps Legend
      • Dec 2019
      • 13992
      • Canada
      #2
      Re: 820-00840 20v 0a

      Post the voltage readings of:

      SMBUS_SMC_5_G3H_SDA
      SMBUS_SMC_5_G3H_SCL

      Next, meter in diode mode. Remove all power to the logic board.

      Red meter probe to ground (yes red probe).

      Black meter probe to:

      SMBUS_SMC_5_G3H_SDA - what is the reading?

      Repeat to test,

      SMBUS_SMC_5_G3H_SCL.

      Post the diode mode measurements for both.

        Comment

        • powerblackout
          Senior Member
          • Feb 2018
          • 109
          • USA
          #3
          Re: 820-00840 20v 0a

          0.421 Diode for both
          3.418V for both, pulsing about every second.

            Comment

            • mon2
              Badcaps Legend
              • Dec 2019
              • 13992
              • Canada
              #4
              Re: 820-00840 20v 0a

              SMBUS measurements are good.

              PP3V3_S5G - 0V with 0.7ohm short to ground
              Missed this post from earlier. This is the power rail for the PCH. This is not good. Wait on feedback from others but this may be a show stopper.

              Is PPBUS_G3H @ F7000, pin # 2 also power cycling ?

              If yes, remove the fuse @ F7000 off the board (without the fuse) and then power up again and check the voltage @ F7000, smd pad # 1.

              What voltage do you read for PPBUS_G3H ? Is it stable (not pulsing) ?

              Remove all power - meter in resistance mode. Measure the resistance to ground for F7000, pin # 2 (downstream = consumer side) of this power rail.

              Post the resistance measurement.

                Comment

                • Simplebeans
                  Senior Member
                  • Sep 2021
                  • 130
                  • UK
                  #5
                  Re: 820-00840 20v 0a

                  Originally posted by powerblackout

                  more measurements:
                  PM_EN_P3V3S5G - 3.3V
                  PP3V3_S5G - 0V with 0.7ohm short to ground
                  mon2 and powerblackout I have a MacBook Pro A1708 with the 820-00840 logic board with me here if there is a reference required, where did you take that resistance measurement?
                  Last edited by Simplebeans; 03-19-2022, 10:55 AM.

                    Comment

                    • powerblackout
                      Senior Member
                      • Feb 2018
                      • 109
                      • USA
                      #6
                      Re: 820-00840 20v 0a

                      I measured at U8205 pin 13/14. I have a donor board that has several 10k ohm resistance in the same spot.

                      The SDL/SDA lines aren't "cycling", just pulsing up and down half a volt.
                      PPBUS_G3H is steady 13V, no cycling.

                        Comment

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