Macbook air 2020 (820-01958) with water damage not turning on

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  • MKesenheimer
    New Member
    • Jan 2023
    • 5
    • <s>KNAsldkn</s>
    #1

    Macbook air 2020 (820-01958) with water damage not turning on

    Dear all,

    I have a Macbook Air 2020 13” (820-01958) with water marks around U8700, C7665 and U2800 in front of me. The laptop is not turning on but the CPU is getting warm after a while.
    I am trying to figure out which component is potentially dead. For that I made the following measurements:

    Voltages on T2 chip rails:
    PP1v8_SLPS2R = 1.80V
    PP1v8_AWAKE = 1.80V
    PP1V8_SLPS2R_PMUVDDGPIO = 1.80V
    PP1v1_SLPS2R = 1.10V
    PP0v8_SLPS2R = 0.80V
    PP0v82_SLPDDR = 0.82V
    PP3v3_AWAKE = 3.28V
    PPVDDCPUSRAM_AWAKE = 0.80V
    PP0v9_SLPDDR = 0.90V
    PP1v1_SLPDDR = 1.10V
    PP1v2_AWAKE = 1.20V
    PPVDDCPU_AWAKE = 0.53V

    Voltages for boot process:
    PP3v_G3H = 2.99V
    PP5v_G3S = 5.07V
    PP3v3_G3S = 3.28V
    PP1v8_G3S = 1.80V

    BridgeOs boot:
    PP1v8_VCCQIO_SSD0 = 1.80V
    PP0v9_SSD = 0.90V
    PPVCC_NAND_SSD0 = 2.52V

    CPU PCH:
    PP3v3_S5 = 3.28V
    PP1v8_PRIM_PCH = 1.81V

    S5 and S4:
    PM_SLP_S4_L = 3.28V (steady)
    PM_SLP_S5_L = 3.28V (steady)
    PP1v8_S3 = 1.81V
    PP1v1_S3 = 1.10V
    PP0v6_S3 = 0.61V

    S3 and S0:
    PM_SLP_S3_L = 3.28V (steady)
    PM_SLP_S0_L = 3.28V (steady)
    PPVCCIN_AUX_PCH = 1.80V
    PP1v05_PCH_CPU = 1.03V (steady)
    PP1V1_S0SW_CPU_VCCPLL_OC = 1.10V
    PP1v8_S0SW_CPU = 1.81V
    PPVCC_S0_CPU = 0.01V


    Diode mode measurements
    PP1v8_SLPS2R = 1.133
    PP1v8_AWAKE = 0.911
    PP1V8_SLPS2R_PMUVDDGPIO = 1.541
    PP1v1_SLPS2R = 0.459
    PP0v8_SLPS2R = 0.906
    PP0v82_SLPDDR = 0.026
    PP3v3_AWAKE = 1.350
    PPVDDCPUSRAM_AWAKE = 0.333
    PP0v9_SLPDDR = 0.038
    PP1v1_SLPDDR = 0.359
    PP1v2_AWAKE = 0.517
    PPVDDCPU_AWAKE = 0.009
    PP1v1_S3 = 0.279
    PPVCC_S0_CPU = 0.00

    The measurements that seem odd to me are marked red.
    I also noticed a frequent clicking sound (around 30Hz) that may come from an inductor in the area around the CPU. But I am not sure where it exactly comes from.
    In a different thread I read that this clicking sound may come from a defective CPU, however, the S3 power rail for the CPU (PP1v1_S3) and PP1v05_PCH_CPU seem ok.
    The system status LED also glows dimly white.

    I have done alle measurements with a logic board that had all peripherals completely unplugged.

    Is it safe to assume that the CPU is indeed dead or should I continue my search? How can I reassure that the CPU is dead? What would be the next logical step to continue?

    Many thanks,
    Matthias
    Last edited by MKesenheimer; 01-05-2023, 08:42 AM.
    Tags: None
    • mon2
      Badcaps Legend
      • Dec 2019
      • 14117
      • Canada
      #2
      Re: Macbook air 2020 (820-01958) with water damage not turning on

      Measure the resistance to ground of the cpu power rail. Appears to be a shorted CPU.

        Comment

        • MKesenheimer
          New Member
          • Jan 2023
          • 5
          • <s>KNAsldkn</s>
          #3
          Re: Macbook air 2020 (820-01958) with water damage not turning on

          Resistances to ground of the CPU power rails are:

          PPVCC_S0_CPU = 0Ω / 0V (in diode mode)
          PP1V1_S3 = 320Ω / 0.28V
          PP1V8_S0SW_CPU = 1.18kΩ / 0.82V
          PP1V05_S0_CPU_VCCST = 550Ω /0.41V
          PP1V05_S0_VCCSTG = 492Ω / 0.19V
          PP1P05_S0_CPU_VCCPLL = 333Ω / 0.33V

          * Edit *
          ALL_SYS_PWRGD = oscillating around 1.5V with 34Hz
          CPU_VR_EN = oscillating around 0.8V with 34Hz
          VCORE voltages = 5.0V
          Last edited by MKesenheimer; 01-05-2023, 02:36 PM.

            Comment

            • mon2
              Badcaps Legend
              • Dec 2019
              • 14117
              • Canada
              #4
              Re: Macbook air 2020 (820-01958) with water damage not turning on

              To me, it looks like a dead CPU but one extra step you can take to confirm is to lift up one leg of each of the multiphase power rail coils.

              Read in full before proceeding...

              That is, lift up one leg of L7210, L7220, L7230.

              After doing this, measure the resistance to ground again of the same power rail that powers the CPU.

              Now, if you continue to see the 0 ohm to ground resistance, the CPU is for sure shorted. Otherwise, one of the power supply devices is at fault.

              This could be U7210, U7220 or U7230.

              Wait on other comments but the above is a worthwhile effort to confirm the short condition.

              Alternatively, if you inject 1 volt (not higher) @ 2A-5A onto this shorted rail - who heats up? Remove the heatsink to confirm.

              Is it the cpu ? If yes, the CPU is shorted.

                Comment

                • MKesenheimer
                  New Member
                  • Jan 2023
                  • 5
                  • <s>KNAsldkn</s>
                  #5
                  Re: Macbook air 2020 (820-01958) with water damage not turning on

                  Alright thank you. I'll wait if someone else has another suggestion. If not, I will try your suggestions tomorrow.

                    Comment

                    • MKesenheimer
                      New Member
                      • Jan 2023
                      • 5
                      • <s>KNAsldkn</s>
                      #6
                      Re: Macbook air 2020 (820-01958) with water damage not turning on

                      Ok, so I did what you suggested. The short remained after I removed the inductors. As I injected 1V to the shorted rail, the CPU warmed up.
                      Now it's pretty clear that the CPU is damaged.

                      Thank you very much for your help.

                        Comment

                        • Rickkap
                          Senior Member
                          • Aug 2015
                          • 129
                          • UK
                          #7
                          Re: Macbook air 2020 (820-01958) with water damage not turning on

                          Old thread but i have exactly the same symptoms. Is it possible to swop the CPU/PCH with one that is working or is it tied to the board like the T2??

                            Comment

                            • incorrect
                              Member
                              • Nov 2017
                              • 22
                              • Greece
                              #8
                              Here i am too. PPVCC_S0_CPU to GND 0 ohm.1V injection while the phases coils are removed drops to 0.75V @ 5A. There is a thermal production on or around CPU but i can't say that the CPU becomes hot. tbh nothing that is connected to PPVCC_S0_CPU becomes hot. Even after 5 minutes of 1V injection. any idea? Device had only a small spot of corrosion on R7673 and C7673 just next to U7650.
                              Last edited by incorrect; 11-25-2023, 03:33 AM.

                                Comment

                                • mon2
                                  Badcaps Legend
                                  • Dec 2019
                                  • 14117
                                  • Canada
                                  #9
                                  ….
                                  Last edited by mon2; 01-10-2025, 03:48 AM. Reason: Wrong thread post

                                    Comment

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