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MacBook A1397 820-3332 No Display/No POST help!

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    MacBook A1397 820-3332 No Display/No POST help!

    A1397 - Laptop turns on as usual. No chimes or Caps Lock behavior, no backlight. Fan spin normal. Attached are V readings. I've isolated all components. 2 Batteries. 3 different chargers. Green Light on adapter. Board: 820-3332 - I've touched up the connections around the U8900.
    History: Client brought it to me one time - I tried different charger and it worked, left it as that.

    It came back in 2 days as expected, did a full clean up of motherboard - so much dust. It works again. Comes back after 1 week same issue. I've checked both sides of board, all clean no corrosion under microscope. I relowe with flux most ICs except major chips CPU/PCH/GPU etc, just the QFN smaller chips ensuring solid soldering and no dirt. Still the same. Turns on fan spin normal, no further post.

    SOME S0 VOLTAGES:
    PP1V05_S0 1.05
    PPVCORE_S0_CPU 0.897
    PPVCORE_S0_AXG 0V
    PP1V5_S3RS0_CPUDDR 1.34V
    PP3V3_S0 3.34V
    PP1V05_PCHVCCIO_S0 1.062V
    PP1V8_S0 1.8V
    PP5V_S0 5.04V
    P1V8S0_PGOOD 3.33V
    P1V8S0_FB 0.79V
    SMC_RESET_L 3.38V

    This guy is missing as per ChatGPT 🙂
    PPVCORE_S0_AXG is a voltage rail that supplies power to the core logic and graphics processing unit (GPU) of a computer system. The "PPV" in the name stands for "positive power voltage," indicating that it is a voltage supply rail.
    In the context of a MacBook or other Apple computer, the "S0" in the name indicates that this voltage rail is active when the system is in the "S0" state, which is the normal operating state when the computer is running. The "AXG" in the name refers to the integrated graphics processor (IGP) that is built into the CPU of the computer.
    PPVCORE_S0_AXG typically supplies a voltage in the range of 0.7V to 1.2V to power the core logic and graphics processing units of the computer. The specific voltage value may depend on the specific model and configuration of the computer system.

    What else can I check? Thanks!

    #2
    Re: MacBook A1397 820-3332 No Display/No POST help!

    Updated Images
    Attached Files

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      #3
      Re: MacBook A1397 820-3332 No Display/No POST help!

      I think I found the issue. L8960 and l8930 are 10 Ohms - OK, GFXIMVP_PHASE1/2
      L7560 CPUIMVP_PHASE2G, CPUIMVP_PHASE1G, CPUIMVP_PHASE1, PPVCORE_SO_CPU_PH2, CPUIMP_PHASE3_L 0.30 Ohms - possible CPU short.

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        #4
        Re: MacBook A1397 820-3332 No Display/No POST help!

        No I don't thin CPU is shorted.
        CPUIMP_PHASE2 0.914V
        CPUIMP_PHASE3_L 0.929V
        PPVCORE_SO_CPU_PH1 is 0.915V
        CPUIMVP_PHASE2G, CPUIMVP_PHASE1G is 0V
        GFXIMVP_PHASE1 0.905V
        GFXIMVP_PHASE2 0.905V

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          #5
          Re: MacBook A1397 820-3332 No Display/No POST help!

          At 16.5V it pulls 1.69Amps then increases to 1.85Amps constantly.
          Last edited by sikocan; 03-06-2023, 02:08 AM.

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