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Macbook A1708 / 820-00840-A / No boot

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    Macbook A1708 / 820-00840-A / No boot

    Hi,

    With the Logic Board connected to the DC source, in the USB-C adapter it gives 19.75V and the current is mostly at zero volts and from time to time it peaks at 0.035A (for about a second).
    I was able to find the source of the anomaly, that is, the PP1V_S5G rail is shorted.

    I know it's not advisable to inject voltage, but that's what I did and with the help of an infrared camera I saw that the processor is the only component to heat up.
    With this, is it correct to conclude that the source of the short is in the processor?

    Best regards.

    #2
    Re: Macbook A1708 / 820-00840-A / No boot

    Ouch! I think so but wait on others to chime in.

    What voltage did you inject?

    We repaired the same logic board with the same current draw a few weeks ago - 8 hours later on the review (no microscope), found the issue was due to the ISL9239 not communicating over SMBUS. The ESD diodes caked up and caused a haul down on the SDA / SCL lines.

    Do you have PPBUS_G3H ? We did not. Then replaced the ISL9239 and one of the mosfets. Neither helped. Then cried a bit and almost thought of start drinking but calmed down and logically traced all parts for the ISL.

    In our case, the voltage on the SMBUS line - SCL I believe was too low. The SDA was @ 3v3. Removed the part and the board came back to life.

    Arrow has the tiny tiny tiny parts for the ESD TVS function.

    Fairly sure that Apple had a design weakness on this logic board where the display connector (backlight voltage to be exact) would short to the CPU rail causing this destructive event.

    Review these:

    https://boards.rossmanngroup.com/thr...shorted.52266/

    Comment


      #3
      Re: Macbook A1708 / 820-00840-A / No boot

      Do review this excellent webpage:

      https://repair.wiki/w/A1708_2016,_20...ar_MacBook_Pro

      My post is the last one

      Comment


        #4
        Re: Macbook A1708 / 820-00840-A / No boot

        Originally posted by mon2 View Post
        Ouch! I think so but wait on others to chime in.

        What voltage did you inject?

        We repaired the same logic board with the same current draw a few weeks ago - 8 hours later on the review (no microscope), found the issue was due to the ISL9239 not communicating over SMBUS. The ESD diodes caked up and caused a haul down on the SDA / SCL lines.

        Do you have PPBUS_G3H ? We did not. Then replaced the ISL9239 and one of the mosfets. Neither helped. Then cried a bit and almost thought of start drinking but calmed down and logically traced all parts for the ISL.

        In our case, the voltage on the SMBUS line - SCL I believe was too low. The SDA was @ 3v3. Removed the part and the board came back to life.

        Arrow has the tiny tiny tiny parts for the ESD TVS function.

        Fairly sure that Apple had a design weakness on this logic board where the display connector (backlight voltage to be exact) would short to the CPU rail causing this destructive event.

        Review these:

        https://boards.rossmanngroup.com/thr...shorted.52266/
        I injected 1.5V and 200mA. I started with 1V and 100mA, but it wasn't enough to see which component went into overload (heating) first.

        First I detected that the voltage drop on L7030 was not stable at 13V. It was constantly varying between 0.4V and 1.15V.
        Then I checked on the U7000, which also had various input and output voltages fluctuating.

        As I couldn't find any reason for this behavior or short circuit, I went to check the behavior of the U1900. It was here that I found the PPVIOE_PCHCLK (2) line shorted (caused by the short in the PP1V_S5G voltage).

        I'll review your post and the other link you shared.

        As soon as possible I will give feedback.

        Thank you very much.

        Comment

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