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A2141 - 5V/0A - liquid damage

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    A2141 - 5V/0A - liquid damage

    Hello,

    I have Macbook A2141 with minor liquid damage. I already cleaned PCB and done some measurements.

    I noticed that PPBUS_G3H is missing. So I removed F7000 and F7001.
    There is 12.25V on PPVBAT_G3H_CHGR_REG
    PPBUS_G3H > ground is about 1Ω. So, there is a short.

    I didn't find much informations about this model.

    Could someone help me, what to check next?

    Thanks

    Marty

    #2
    Re: A2141 - 5V/0A - liquid damage

    Which side of PPBUS_G3H is with the low resistance?

    Is it the producer side (ISL) or the consumer side?

    Post the details of the pin # of the removed fuse pcb pad for this measurement.

    Comment


      #3
      Re: A2141 - 5V/0A - liquid damage

      Hello, thanks for reply

      On F7000 pin #1 there is 12.25V

      On F7000 pin #2 there is 0V (shorted-1Ω to ground)

      On F7001 pin #1 there is 12.25V

      On F7001 pin #2 there is 0V (shorted-1Ω to ground)

      Comment


        #4
        Re: A2141 - 5V/0A - liquid damage

        On F7000 pin #2 there is 0V (shorted-1Ω to ground)
        On F7001 pin #2 there is 0V (shorted-1Ω to ground)
        It is possible that you have a shorted high side mosfet on the CPU rail.

        Measure the resistance between F7000/F7001 pin #2 (either is ok) and the Vcore rail that powers the CPU.

        That is, the PPBUS_G3H is considered the high voltage to power the logic board. The Vcore voltage is built upon a high and low side mosfet that switch on/off to dial down the high voltage to a much lower safe voltage for the CPU.

        If the high side mosfet is leaky, the CPU will be damaged.

        Post the measurement. The next logic step is use a DC lab power supply to dial up 1 volt and inject this voltage onto the same low resistance side of the fuses. Then monitor the current draw and also which component(s) heat up. The CPU can be confirmed if the heat sink is removed.

        The general rule is to keep the voltage for injection to a low value to protect the CPU - in case it is still alive.

        Comment


          #5
          Re: A2141 - 5V/0A - liquid damage

          It's from F7000/F7001 pin #2 > PPVCC_S0_CPU

          Comment


            #6
            Re: A2141 - 5V/0A - liquid damage

            So, does it mean CPU is burned?
            Last edited by martyjelen; 07-11-2023, 06:25 AM.

            Comment


              #7
              Re: A2141 - 5V/0A - liquid damage

              I think you are ok here but best to check against a known good board.

              Reference:
              https://boards.rossmanngroup.com/thr...-ground.37575/

              Would you have an adjustable power supply?

              Dual it to 1 volt. Red power supply probe on the ppbus_g3h line with the short. Black power lead to ground.

              With this setup; no other power adapter or battery; who is heating up? Is it the CPU or some capacitor?

              Comment


                #8
                Re: A2141 - 5V/0A - liquid damage

                I don't have much to lose with this case. I dialed up 1V to ppbus_g3h. Nothing seems to get hot.

                Comment


                  #9
                  Re: A2141 - 5V/0A - liquid damage

                  What is the current draw on your power supply during this injection? Is the heatsink on or off the CPU?

                  Comment


                    #10
                    Re: A2141 - 5V/0A - liquid damage

                    Current draw is about 750mA. Heatsink is on, but I check PCB with thermal camera, so I think it should be visible, if something is wrong with CPU or am I wrong?

                    Comment


                      #11
                      Re: A2141 - 5V/0A - liquid damage

                      Is the power supply being current limited to 750 mA? Can it support higher current?

                      Comment


                        #12
                        Re: A2141 - 5V/0A - liquid damage

                        I set limit to 5A. Current draw is still 750mA.

                        Comment


                          #13
                          Re: A2141 - 5V/0A - liquid damage

                          While injecting this 1 volt from your dc power supply, measure the voltage to ground at PPVCC_S0_CPU. Do you see a voltage reading?

                          Comment


                            #14
                            Re: A2141 - 5V/0A - liquid damage

                            There is nothing. 0V.

                            Comment


                              #15
                              Re: A2141 - 5V/0A - liquid damage

                              Review the resistance to ground of L9581 and L9081 as noted here:

                              https://repair.wiki/w/A2141_2019_16%22_MacBook_Pro

                              Comment


                                #16
                                Re: A2141 - 5V/0A - liquid damage

                                Seems OK, there is more than 1k ohms.

                                Comment


                                  #17
                                  Re: A2141 - 5V/0A - liquid damage

                                  Is your meter auto ranging or manual select for the resistance scales?

                                  Can you post a pic of the meter face while taking this 1 ohm reading?

                                  Suspecting that perhaps the meter is stating the resistance is higher than the selected scale with the "1" = over limit. So you need to use the next higher meter scale till you have a valid measurement.

                                  Comment


                                    #18
                                    Re: A2141 - 5V/0A - liquid damage

                                    I can select ranges. Did you mean that 1ohm reading from PPBUS_G3H > ground?

                                    If I change range to kΩ, it shows 0,001kΩ

                                    Comment


                                      #19
                                      Re: A2141 - 5V/0A - liquid damage

                                      So, it really reads 0,9Ω-1Ω from PPBUS_G3H > ground.

                                      Comment


                                        #20
                                        Re: A2141 - 5V/0A - liquid damage

                                        Short your meter probes. What is the resistance?

                                        Comment

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