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820-3476 No boot or Odd Boot

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  • 820-3476 No boot or Odd Boot

    Retina no drop or liquid damage

    Started off randomly failing to come out of sleep.

    Now the computer rarely will turn on from completely off

    Plug in charger you get a green light that turns orange
    Battery unplugged the computer boots itself when charger plugged in
    Backlight sometimes comes on with no image but only occasionally does back light turn on. When it does turn on backlight voltage is 37V
    There is no chime on backlight turning on and no chime any other time
    No output to external monitor. USB mouse does turn on the red led optical sensor

    Checked all the main voltages on the schematic and all the PM SLP rails everything is there but the computer will not boot.
    PPVCore is there
    DDR is there
    3v3 is there
    5v is there
    G3H is there
    PM SLP s5/s4/s3/s0 are there read 3.3v

    Is this a BIOS issue? Bad PCH? Local apple store brought it to me and said it had passed ASD when on and working.
    B&C Connection LLC
    Chris Long

  • #2
    Does the mouse turn on when the computer does not boot? Do a PRAM reset and see if audio comes back.

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    • #3
      Tried PRAM no difference. Occasionally after PRAM or SMC reset I get Backlight but still no image.
      The USB mouse turns on everytime you "boot" the laptop and fan spins every time. LCD panel never turns on but does have voltage. Backlight rarely turns on but when it does has 37v.
      If hooked up via HDMI or Thunderbolt I get no external display
      B&C Connection LLC
      Chris Long

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      • #4
        Disconnect internal LCD and it should display through thunderbolt. I still suspect the LCD assembly.

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        • #5
          Duke you were correct. LVDS disconnected and it outputs to external monitor.

          Looks like new screen on the way. Never seen that before.
          B&C Connection LLC
          Chris Long

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