Macbook Pro 13" - A1989 - 820-00850-A - No Power Issue

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  • reessi
    Badcaps Veteran
    • Jan 2016
    • 332
    • uk

    #1

    Macbook Pro 13" - A1989 - 820-00850-A - No Power Issue

    Hello,

    This Macbook does not turn on:

    The power button is ripped, I received it like this and the machine was working fine with a ripped power button as boots when plugged in.

    Current state:

    When plugged in the USB meter goes to 20v /~0.5 gradually increasing to 0.7a charging for 10s then resets charging but remains at 20v, current draw drops to around ~40/50mah then restarts a second later looping.. all 4 ports are the same.

    The touchpad responds (vibrating when pressed) but also is cycling on and then off.

    PP3V_G3S -> Present (3.35v) on Battery or just Charger, NOT cycling, always present!
    PP5V_G3S -> Present (5.12v) on Battery or just Charger, NOT cycling, always present!
    3v3_G3H_RTC -> 3.3v on Battery or just Charger.

    There is 3.3v on the Power button connector and when shorted to ground nothing happens.
    The fans do not spin at any point..


    I am not sure where to go from here, is this a charging fault with the CD3215 IC's or something else.

    I have checked as many areas as possible for shorts, all inductors I have seen and checked on the board are not short.


    U7800 has no shorts in the output inductors and has voltages present on several of them.. I am not sure if at this point all of them should be on..
    The voltages present on U7800 turn off for a split second when the charging resets!

    Voltages present on u7800 (Some have multiple outputs and are all present):

    PP1V8_SLPS2R -> 1.8v
    PP0V9_SLPDDR -> 0.9v
    PP1V1_SLPS2R -> 1.1v
    PPVDDCPU_AWAKE -> 0.74v
    PP0V82_SLPDDR -> 0.81v
    PPVDDCPUSRAM_AWAKE -> 0.79v

    MISSING (Not sure if should be present at this stage):

    PVCCPCOREPRIM -> 0v (SW0 & SW1)
    P1VPRIM -> 0v (SW0 & SW1)


    On the charger with battery dis-connected:


    PP_G3HOT:
    12.55v @ 38mah then every 30s it changes to 12.22v @ 60mah!!

    Battery is currently at 11v.

    I can upload photos of the board and I have the boardview and schematics from this forum.

    I have thoroughly inspected the board under the microscope and no damage can be seen.

    Many thanks.
    Last edited by reessi; Today, 09:48 AM.
  • mon2
    Badcaps Legend
    • Dec 2019
    • 14280
    • Canada

    #2
    Flux and remove the fuse @ F7000. Then power up again.

    Measure the voltage to ground on F7000, pcb pad # 1 on the PCB at the site of the removed fuse. Is the voltage stable? What is the voltage?

    Comment

    • reessi
      Badcaps Veteran
      • Jan 2016
      • 332
      • uk

      #3
      Hi mate,

      Pin 1 shows 12.22v no changes after removal with battery connected and charger.

      1.4v with just battery.

      And 12.22v with charger no battery.

      It is stable, 12mah consumption on the USB C meter in all cases.

      Cheers.

      Comment

      • mon2
        Badcaps Legend
        • Dec 2019
        • 14280
        • Canada

        #4
        Attach the power adapter only. Carefully measure the voltage to ground on each pin on the battery connector @ J6951.

        Post each measurement. We are testing if the SMBUS interface lines are ok or if one of the TVS ESD diodes has become defective.

        Click image for larger version

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        Comment

        • reessi
          Badcaps Veteran
          • Jan 2016
          • 332
          • uk

          #5
          Actually I already checked SCL and SDA earlier due to seeing that in another thread.. But checked again now:

          1 -> 0v
          2-> 3.3v
          3-> 3.3v
          4-> 0v

          By the way nothing is in those lines when the fuse is removed. Also with the fuse removed the USB meter stays at 5v... Is this expected?

          Comment

          • reessi
            Badcaps Veteran
            • Jan 2016
            • 332
            • uk

            #6
            Sorry actually the voltage is cycling quickly, 3.3v, 3v, 2.84v, something like that but probably too quick for my multimeter!

            Same on both lines.

            Diode readings if helpful:

            SCL - 1300
            SDA - 1255

            OK just realised you said with charger only... On charger only the voltage is stable at 3.34v well occasionally changes to 3.32v but I don't think that is anything. It cycles with the battery connected.
            Last edited by reessi; Today, 02:39 PM.

            Comment

            • mon2
              Badcaps Legend
              • Dec 2019
              • 14280
              • Canada

              #7
              These lines are fine. They are not shorted. If these lines reported a low voltage then one of the diodes is shorted.

              Remove all power. Meter in resistance mode. Measure the resistance to ground of each and every inductor on the board. You are hunting for a short on one of the power rails. If the resistance is too low, then the rail may have a short on that power rail and causing the power cycling.

              Comment

              • reessi
                Badcaps Veteran
                • Jan 2016
                • 332
                • uk

                #8
                I already did that on every inductor I could find, none are low except the CPU ones as expected.

                I'll do some checking again but I spent quite some time looking for shorts so far..

                What about the missing outputs on U7800?
                Should they be on at this stage or come on later?

                PVCCPCOREPRIM -> 0v (SW0 & SW1)
                P1VPRIM -> 0v (SW0 & SW1)

                I'm going to work through all the power rails one by one from the schematic and see if any are short..
                Last edited by reessi; Today, 03:25 PM.

                Comment

                • mon2
                  Badcaps Legend
                  • Dec 2019
                  • 14280
                  • Canada

                  #9
                  Do you have a power sequence chart for this model?

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                  Click image for larger version

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                  Last edited by mon2; Today, 06:58 PM.

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