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820-01041-A no 20V

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  • 820-01041-A no 20V

    Hi,



    I’ve got an 820-01041-A that is driving me crazy, so I’m here for a 2nd opinion. I know these boards are fairly new, so there is not that much info out there.



    The problem is I can’t get this board to get 20V from the charger. PP20V_USBC_TA_VBUS remains at 5V.



    So, I get the following voltages



    PP20V_USBC_TA_VBUS = 5.15V @ 0.06A

    = PP3V3_G3H_T = 3.374V

    = PP3V3_G3H_RTC_X = 3.383V

    = PP1V8_G3S = 0.0V

    = PPBUS_G3H = 12.29V

    There are no G3S voltages



    PMU_CLK32K_PCH = 32.768Khz



    I have swapped out all 4 CD32. In case any where faulty.
    Still no PP20V!



    These are the CD32 Voltages



    PP1V8_SLPS2R = 1.802V

    PP1V1_UPC_ = 1.11V

    PP3V3_UPC = 3.335V

    PP5V_S4_X_USBC = 0.0V



    There is data on USBC_XA_CC1_CONN. So the charger is talking to CD32.
    SMC Reset Circuit



    U6940 voltages

    PMU_ONOFF_L = 3.38V

    PMU_RSLOC_RST_L = 3.38V

    CHGR_RST_IN_R = 0.0V



    Communication with the SMC



    I2C_UPC_SCL = 1.8V

    I2C_UPC_SDA = 1.8V

    UPC_I2C_INT_L = 0V



    There is no activity on these data lines. No pulses at all on my scope.



    T2 Voltages



    PPVDDCPU_AWAKE =0.825V

    PPVDDCPUSRAM_AWAKE =0.802V

    PP0V82_SLPDDR = 0.821V

    PP1V1_SLPDDR 1.1V

    PP0V9_SLPDDR 0.9V

    PP1V2_AWAKE = 1.2V



    The board is crystal clear. No liquid damage I can see, under the microscope.

    Of course, the customer needs some critical data. Since its looking like a SMC and SMC is integrated into U3900 T2 chip its looking hopeless.



    Anyone have any ideas on what else I could try or what I could have missed ?

  • #2
    If the "SOC ROM" gets corrupted there will also not be 20V. This is U4770 on 01521 schematic so probably the same on this one.
    Problem here is if you flash a good binary in there the 20V will be back but the machine will not power on as the ROM is married to the T2 chip.
    So far I do not have enough dumps/machines yet to be able to figure this stuff out. It may be possible to repair the original dump, but I have found that apple has used many different versions of iBoot inside the ROMs. I would need to at least find a known good dump with the same iBoot versions and see if the ROMs can be merged by extracting the unique parts.

    So if you want to mess with this you should read the SOC ROM and find a dump from a good board and flash that in and see if 20V comes back. Then comes the at the moment impossible task of fixing the corrupted ROM.

    !!1.8V ROM MAKE SURE YOU DO NOT READ THIS ON 3V3!!

    Comment


    • #3
      Thanks Duke, i'll give this a crack tomorrow. i've got a few of these machines in i can mess about with.

      Nice to see your still about.

      Comment

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