A1708 820-00840 no power

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  • nassih
    Badcaps Veteran
    • Oct 2015
    • 276
    • morocco

    #1

    A1708 820-00840 no power

    hello everybody my macbook a1708 is giving me some issues:
    no power and no amp consumption i have replaced c7078 was shorted to ground. voltage checked :
    ppbus_g3h=0.3
    ppdcin_g3h_chr_r=5.1v
    ppvin_g3h_p3v3 g3h=3.8v
    pm_en_p3v3_g3h_r=4.6v
    pp3v3_g3h_vr=2.2v (required 3.3v)
    pp3v3_g3h=2.2v (required 3.3v)
    no short to ground
    tanks
  • mon2
    Badcaps Legend
    • Dec 2019
    • 14060
    • Canada

    #2
    Re: A1708 820-00840 no power

    ppbus_g3h=0.3
    STOP.

    Remove the fuse @ F7000. Then, meter in DC volts mode (30V or higher is ok).

    Red meter probe to F7000, pin # 1 (ISL side) PCB pad.
    Black meter probe to ground (shield is ok).

    What is the voltage to ground ?

    Next, meter in RESISTANCE mode. Remove all power.

    Check the resistance to ground of F7000, pin # 2 (downstream / consumer side) PCB pad.

    One meter probe on F7000, pin # 2 PCB pad.
    Other meter probe to ground.

    What is the resistance to ground ? Make a note of the meter scale if it is not automatic scaling.

    Post your readings. From the very low voltage, sounds like you have a shorted capacitor on the downstream / consumer side of the logic board.

    Comment

    • nassih
      Badcaps Veteran
      • Oct 2015
      • 276
      • morocco

      #3
      Re: A1708 820-00840 no power

      tanks sir for reply.ok I will do all that tonight, I also want to inform you that after replancement of diode D6905 the voltages have changed:
      ppdcin_g3h_chr_r= 20v
      pp3v3_g3h_vr= 3.4v
      pp3v3_g3h= 3.4v
      ppbus_g3h=0.3

      Comment

      • nassih
        Badcaps Veteran
        • Oct 2015
        • 276
        • morocco

        #4
        Re: A1708 820-00840 no power

        voltage on F7000 pin 1 = 0.123v
        when I was measuring the voltage across f 7000, I noticed that f 7000 has a high resistance about 470k,replaced from donor board same issue

        Comment

        • mon2
          Badcaps Legend
          • Dec 2019
          • 14060
          • Canada

          #5
          Re: A1708 820-00840 no power

          Do you have F7000 removed or on the board ?

          The fuse must be removed to check if the PPBUS_G3H voltage rail is being generated.

          Comment

          • nassih
            Badcaps Veteran
            • Oct 2015
            • 276
            • morocco

            #6
            Re: A1708 820-00840 no power

            yes i have removed f7000 but still no generate voltage
            how much voltage should be on f7000 when removed?

            Comment

            • piernov
              Super Moderator
              • Jan 2016
              • 4435
              • France

              #7
              Re: A1708 820-00840 no power

              Bad dual diode and possibly resistor feeding PP3V3_G3H input as always.
              OpenBoardView — https://github.com/OpenBoardView/OpenBoardView

              Comment

              • nassih
                Badcaps Veteran
                • Oct 2015
                • 276
                • morocco

                #8
                Re: A1708 820-00840 no power

                I believe that the diode seems good, I have checked with meter, the last one was open on point 1 and 3
                ppbus_g3h can generate the voltage without battery in?

                Comment

                • mon2
                  Badcaps Legend
                  • Dec 2019
                  • 14060
                  • Canada

                  #9
                  Re: A1708 820-00840 no power

                  ppbus_g3h can generate the voltage without battery in?
                  Yes. One leg of the dual diode is a feed from the battery.

                  Other leg of the dual diode is a feed from the external power adapter.

                  The diode will select the higher of the 2 sources to create the PPVIN_G3H_P3V3G3H.

                  This input feeds the regulator @ U6990.

                  Review the voltage to ground on each leg of D6905 (dual ANODE diode).

                  Next, check the voltage to ground of PP3V3_G3H @ L6995, pin # 2.

                  Post each measurement.

                  Comment

                  • nassih
                    Badcaps Veteran
                    • Oct 2015
                    • 276
                    • morocco

                    #10
                    Re: A1708 820-00840 no power

                    the voltage on D6990:
                    pin1: 0,3V
                    pin2: 20V
                    pin3: 19
                    PP3V3_G3H on L6995: 0,23v

                    Comment

                    • nassih
                      Badcaps Veteran
                      • Oct 2015
                      • 276
                      • morocco

                      #11
                      Re: A1708 820-00840 no power

                      sorry its D6905 not D6990

                      Comment

                      • mon2
                        Badcaps Legend
                        • Dec 2019
                        • 14060
                        • Canada

                        #12
                        Re: A1708 820-00840 no power

                        So this rail is missing. This rail may have a shorted part on this leg.

                        Remove all power. Meter in resistance mode.

                        Measure the resistance to ground of L6995.

                        Post the resistance reading.

                        Comment

                        • nassih
                          Badcaps Veteran
                          • Oct 2015
                          • 276
                          • morocco

                          #13
                          Re: A1708 820-00840 no power

                          black probe to ground red probe to L6995 :130k
                          red probe to ground black probe to L6995 :2.8k

                          Comment

                          • nassih
                            Badcaps Veteran
                            • Oct 2015
                            • 276
                            • morocco

                            #14
                            Re: A1708 820-00840 no power

                            voltage on L9695 : 3.4v

                            Comment

                            • mon2
                              Badcaps Legend
                              • Dec 2019
                              • 14060
                              • Canada

                              #15
                              Re: A1708 820-00840 no power

                              From post # 10

                              PP3V3_G3H on L6995: 0,23v
                              Which is correct ?

                              Comment

                              • nassih
                                Badcaps Veteran
                                • Oct 2015
                                • 276
                                • morocco

                                #16
                                Re: A1708 820-00840 no power

                                sorry PP3V3_G3H is 3.4v

                                Comment

                                • mon2
                                  Badcaps Legend
                                  • Dec 2019
                                  • 14060
                                  • Canada

                                  #17
                                  Re: A1708 820-00840 no power

                                  the voltage on D6990:
                                  pin1: 0,3V
                                  pin2: 20V
                                  So PPBUS_G3H is now @ 20V ?


                                  Can you confirm this? What changed ?

                                  Comment

                                  • nassih
                                    Badcaps Veteran
                                    • Oct 2015
                                    • 276
                                    • morocco

                                    #18
                                    Re: A1708 820-00840 no power

                                    checking resistance between PPBUS_G3H and the output of buck converters:
                                    L8030: 1m
                                    L8060: 0.8m
                                    L7960:
                                    L7900:
                                    L7730: 1.5m
                                    L7690: 15m
                                    L7670: 12m
                                    L7430: 8m
                                    L7370: 7m
                                    L7220: 6m

                                    Comment

                                    • nassih
                                      Badcaps Veteran
                                      • Oct 2015
                                      • 276
                                      • morocco

                                      #19
                                      Re: A1708 820-00840 no power

                                      Originally posted by mon2
                                      So PPBUS_G3H is now @ 20V ?


                                      Can you confirm this? What changed ?
                                      no sir PPBUS_G3H is 0.037v

                                      Comment

                                      • nassih
                                        Badcaps Veteran
                                        • Oct 2015
                                        • 276
                                        • morocco

                                        #20
                                        Re: A1708 820-00840 no power

                                        to confirm:
                                        PPDCIN_G3H_CHGR_R : 20v(pin2 D6905)
                                        PPBUS_G3H_R : 0.037v (pin1 D6905)
                                        PPVIN_G3H_P3V3G3H :19.76v (pin3 D6905)

                                        Comment

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