MACBOOK A1989 820-00850

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  • PITERPENY
    Badcaps Veteran
    • Jul 2023
    • 455
    • Ukraine
    #1

    MACBOOK A1989 820-00850

    Hello. Need a fresh look. MacBook shows no signs of life.
    When connected to USB-C with the battery connected, the consumption is 20V/0.220A and PPBUSG3H=11V.
    If you disconnect the battery, the consumption will be 5V/0.220A and PPBUSG3H=12.3V
    PP3V3_G3H=3.3V
    PP5V_G3S=0V
    PP1V8_SLPS2R =1.8v =0v=1.8v =... cyclically
    voltage around u7800 appears/disappears cyclically.
    Tags: None
    • ugamazing
      Senior Member
      • Jun 2013
      • 165
      • usa
      #2
      Is PP1v8_SLPS2R shorted? It should be stable. Might be a faulty T2. Are other T2 rails stable or do they all cycle?

      Also, the change in PPBUS when disconnecting battery is unusual; ppbus will be lower on battery and higher on charger(+batt). Have you tried testing board with a known-good case/battery and also DFU restore?

      What work has been done on the board if any? Any signs of damage/liquid near any USB-C controllers at all? 20v/0a can be a ROM issue also, keep in mind. You can swap the ROM or reprogram with clean dump to be sure.

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          thanks...
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