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820-00840 dead 19.7v and 0.01A

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    820-00840 dead 19.7v and 0.01A

    Hi all,

    i am working on macbook pro A1708 820-00840-A.
    no history..customer just brought and say cannot turn on.

    i plugged usb c amp meter and got 19.7v and 0.01A
    check PPBUS_G3H 0.425V..check PPBUS_G3H but no short...but when measure for resistance i got 110 ohm on PPBUS_G3H..check for other rail but no short. can someone help?

    #2
    Re: 820-00840 dead 19.7v and 0.01A

    Hi. Do not have a schematic in front of me at this time but often the PPBUS_g3h regulator is powered from a dual common-cathode diode. Search for it and post the voltage on each of the pins.

    One pin is from the 20v adapter.

    One pin will be from the battery.

    Output pin will be to this regulator. This output pin must be close to the input rail value.

    Post the measurements.

    Comment


      #3
      Re: 820-00840 dead 19.7v and 0.01A

      Originally posted by mon2 View Post
      Hi. Do not have a schematic in front of me at this time but often the PPBUS_g3h regulator is powered from a dual common-cathode diode. Search for it and post the voltage on each of the pins.

      One pin is from the 20v adapter.

      One pin will be from the battery.

      Output pin will be to this regulator. This output pin must be close to the input rail value.

      Post the measurements.
      hi mon2,

      here i attached the schematic
      Attached Files

      Comment


        #4
        Re: 820-00840 dead 19.7v and 0.01A

        Thanks. Post the voltages on each pin of D6905.

        My bad, confirm that the 3v42 voltage is stable.

        Then measure the voltage on both sides of F7000 fuse (ppbus_g3h). Still low voltage?

        If yes, power down and remove F7000. Do NOT bypass it.

        Just want to confirm that the power switching circuit is working to produce the ppbus_g3h rail ok.

        What is the voltage if this rail without F7000? You will be measuring the voltage directly at pin #1 of F7000 pad.
        Last edited by mon2; 09-24-2021, 03:33 AM.

        Comment


          #5
          Re: 820-00840 dead 19.7v and 0.01A

          Originally posted by mon2 View Post
          thanks. Post the voltages on each pin of d6905.

          My bad, confirm that the 3v42 voltage is stable.

          Then measure the voltage on both sides of f7000 fuse (ppbus_g3h). Still low voltage?

          If yes, power down and remove f7000. Do not bypass it.

          Just want to confirm that the power switching circuit is working to produce the ppbus_g3h rail ok.

          What is the voltage if this rail without f7000? You will be measuring the voltage directly at pin #1 of f7000 pad.
          d6905:
          Pin 1 0.43v
          pin 2 20.1 v
          pin 3 19.8v

          pp3v3_g3h 3.4v

          took off f7000
          pin ppbusg3h 0.4v
          pin ppvbat_g3h_chrg_reg 13v

          Comment


            #6
            Re: 820-00840 dead 19.7v and 0.01A

            Post the voltage readings on each pin of Q7030. Interested to know the voltage of SOURCE, DRAIN and GATE. Note there are 2 mosfets inside each.

            Do the same for Q7040.

            Comment


              #7
              Re: 820-00840 dead 19.7v and 0.01A

              Adding to your list...

              with F7000 removed, meter in resistance mode, no power to the logic board,

              check & post the resistance to ground for the F7000 pad # 1

              check & post the resistance to ground for the F7000 pad # 2

              This is to allow us to check which side of the fuse is causing this heavy load.

              Comment


                #8
                Re: 820-00840 dead 19.7v and 0.01A

                Originally posted by mon2 View Post
                Adding to your list...

                with F7000 removed, meter in resistance mode, no power to the logic board,

                check & post the resistance to ground for the F7000 pad # 1

                check & post the resistance to ground for the F7000 pad # 2

                This is to allow us to check which side of the fuse is causing this heavy load.
                resistance to ground for the F7000 pad # 1 OL
                resistance to ground for the F7000 pad # 2 115 ohm

                Comment


                  #9
                  Re: 820-00840 dead 19.7v and 0.01A

                  Originally posted by mon2 View Post
                  Post the voltage readings on each pin of Q7030. Interested to know the voltage of SOURCE, DRAIN and GATE. Note there are 2 mosfets inside each.

                  Do the same for Q7040.
                  these measurements without remove the mosfet

                  Q7030
                  PIN 1-3 ------20V
                  PIN 4 ----------0V
                  PIN 5-6 -------GND
                  PIN 7-10 ------0V
                  PIN 11 --------0V
                  PIN 12 --------0V
                  PIN 13 ------20V
                  PIN 14 -------GND

                  Q7040
                  PIN 1-3 --------0.4V
                  PIN 4 -----------0V
                  PIN 5-6 --------GND
                  PIN 7-10 -------0V
                  PIN 11 ---------0V
                  PIN 12 ---------0V
                  PIN 13 ---------0.4V
                  PIN 14 ---------GND

                  Comment


                    #10
                    Re: 820-00840 dead 19.7v and 0.01A

                    Power down. Meter in resistance mode.

                    Please post the resistance readings for these same mosfets:

                    source to drain
                    source to gate
                    gate to drain


                    Review the resistance chart from this website for guidance:

                    http://electronicsbeliever.com/how-t...-is-defective/

                    Comment


                      #11
                      Re: 820-00840 dead 19.7v and 0.01A

                      Originally posted by mon2 View Post
                      Power down. Meter in resistance mode.

                      Please post the resistance readings for these same mosfets:

                      source to drain
                      source to gate
                      gate to drain


                      Review the resistance chart from this website for guidance:

                      http://electronicsbeliever.com/how-t...-is-defective/
                      i assume the mosfet is broken and replace it but still low on ppbus...could it be U7000 ?

                      Comment


                        #12
                        Re: 820-00840 dead 19.7v and 0.01A

                        update for this problem, i replaced U7000 but still no luck..checked again and found out that PP3V3_TBT_X_F is shorted but i check the others PP3V3 line are not shorted..

                        any suggestion?

                        Comment


                          #13
                          Re: 820-00840 dead 19.7v and 0.01A

                          update.. i found the short..it is C2977. but i lost some components when i open the shield. it is D3411, C3408 and D3403..is it ok if i dont replace the missing components regarding is is a supported components for usb C

                          Comment

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