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820-2850-A can't adjust the backlight

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  • 820-2850-A can't adjust the backlight

    The backlight is always on 100%, we have changed the graphic chipset, frame buffer cap, Graphic power controller and backlight driver with no success, any ideas?

  • #2
    Try PRAM reset first.
    Check PWM signal at U9701 (pin 2) when press backlight adjust keys.
    DC scale good enough to see the variation.

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    • #3
      PWM signal is present, but it doesnt vary.
      It also doesnt show it in osx when i press one of the two keys.

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      • #4
        Backlight is adjusted through GMUX (U9600).
        Reflow it and change with one from donor board, if no result.

        One thing, does this machine has EFI password?

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