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820-00165: Not powering up. MagSafe light is green then orange. Missing PP5V_S4RS3

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  • 820-00165: Not powering up. MagSafe light is green then orange. Missing PP5V_S4RS3

    Hello,
    I have another no power logic board that i've been fighting with. Came in with heavy liquid damage. Replaced all the corroded and suspected corroded components but still not getting power on s4. Here are the readings:

    PPBUS_G3H - 8.58v
    PP3V42- 3.4V
    PP5v_S5 - 5V
    PP3v3_S5 - 3.3V
    PPVRTC_G3H- 3.324v
    PP5V_S4RS3 - 0v
    PP3V3_S4 - 0V
    PP3V3_SUS - 3.3v
    SMC_ADAPTER_EN - 3.4v
    PM_BATLOW_L - 3.3v
    PM_RSMRST_L - 3.3v

    cycled SMC_ONOFF_L and went from 3.4v to 0.35v on PM_PWRBTN_L.
    PM_SLP_S4_L also pulses during the SMC_ONOFF_L cycle.


    Any suggestions would be much appreciated. Thanks

  • #2
    Replaced SMC as well with the same result

    Comment


    • #3
      Where was liquid by?

      Comment


      • #4
        If PM_SLP_S4_L pulses, then all S3 voltages should pulse too; i.e. L7520, check that.
        Also check if PM_SLP_S3_L pulses.
        If yes, check if S0 voltages pulse.

        Check for corrosion around u1950.
        Do you get pulse at ALL_SYS_PWRGD?

        Comment


        • #5
          Sign of liquid was at the regions of R1830, J7000, C7131, U7820, U7320, U1845, Q1842, U7840. I replaced U7820, U7320, and surrounding caps and resistors.

          Yes they all pulse when i cycle SMC_ONOFF_L, even ALL_SYS_PWRGD. I did notice however that PP3V3_S4 reads about 0.04v and PP3V3_S3 reads about 0.06V before the pulse.
          No corrosion on U1950

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          • #6
            Looks like it may be the CPU on the 19 caps connected to the PPVCC_S0_CPU line. Measure ground resistance at C1031. So pulled R7310 and R7320. Still reading short. Wondering if i should pull all 19 caps to confirm.

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            • #7
              Liquid around U7320 could caused overvoltage on CPU core; worst scenario in this case...

              "Still reading short."
              Where?
              What is resistance to ground on L7310/20 now?

              Comment


              • #8
                I had pulled L7310/20, ane R7310/20 to isolate the short to either the 19 caps or the cpu. And the reading is 0.98ohms on the caps. On L7310 pad 1, the reading is 40.3K

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                • #9
                  Forgot, but i'm reading short at C1031.

                  Comment


                  • #10
                    Dead CPU.
                    Normal value is higher than 10 ohms in CPU VCORE, for this board.
                    All mentioned caps support more voltage than CPU; is the first who die in case of overvoltage...

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                    • #11
                      Yep that's my conclusion. Thanks for the assist.

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