820-01987 no backlight when wake up from sleep

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  • kingskie
    Badcaps Veteran
    • Oct 2014
    • 249
    • indonesia
    #1

    820-01987 no backlight when wake up from sleep

    Hello,

    I have a problem with 820-01987 that has no backlight when wake up from sleep. before there was water damage around U6903 and backlight caps. no corrosion found so i just clean it up. is there any component that in charge for enable backlight after wake up from sleep mode?

    any suggestion would be appreciated.
    Tags: None
    • kingskie
      Badcaps Veteran
      • Oct 2014
      • 249
      • indonesia
      #2
      Re: 820-01987 no backlight when wake up from sleep

      when no backlight after wake up from sleep mode, i turn off the macbook with power button and then try to power on with power button again. and still no backlight.
      but if i disconnect the battery and reconnect and turn on the macbook, the backlight is on. but backlight off again when wake up from sleep mode. already tried PRAM reset bust still the same.

        Comment

        • mon2
          Badcaps Legend
          • Dec 2019
          • 14340
          • Canada
          #3
          Re: 820-01987 no backlight when wake up from sleep

          Check if the lid switch is working which is a logic level used to tell the logic board the lid is open or closed.

          Believe that is a hall effect (magnetic) sensor linked to the track pad. Check to see if your track pad cable is clean and with proper contact.

          The backlight ic will have an enable pin. When it works, check the enable pin value. When backlight is off, check again.

            Comment

            • kingskie
              Badcaps Veteran
              • Oct 2014
              • 249
              • indonesia
              #4
              Re: 820-01987 no backlight when wake up from sleep

              hi @mon2,

              update:
              now the backlight is fully off even after dissconnect the battery. what should i check first?

                Comment

                • mon2
                  Badcaps Legend
                  • Dec 2019
                  • 14340
                  • Canada
                  #5
                  Re: 820-01987 no backlight when wake up from sleep

                  Same points of interest. The backlight input voltage that is used to boost to create the backlight.

                  What is the voltage before the backlight IC?

                  Enable logic pin on the backlight IC - voltage?

                  The actual backlight voltage value?

                  Does the caps key led toggle? To confirm logic board is booting.

                  Also, this model is impacted by the Flex gate fault where the video cables are too short and get broken over time.

                  https://boards.rossmanngroup.com/thr...ning-on.61731/

                    Comment

                    • kingskie
                      Badcaps Veteran
                      • Oct 2014
                      • 249
                      • indonesia
                      #6
                      Re: 820-01987 no backlight when wake up from sleep

                      hi @mon2,

                      these are my measurements:
                      PPBUS_G3H = 12.58V
                      PPVIN_S0SW_LCDBKLT_R = 12.58V
                      BKLT_SD = 0V
                      LCDBKLT_EN_L = 0V

                      the value for R8402 and R8401 is normal.

                      the caps key led is on, and i can see image but no backlight

                      this is 2020 model, does it have problem with flex gate? i already check the flex gate all looks good.

                      can i use 2016-2018 screen to test with this model?

                      Originally posted by mon2
                      Same points of interest. The backlight input voltage that is used to boost to create the backlight.

                      What is the voltage before the backlight IC?

                      Enable logic pin on the backlight IC - voltage?

                      The actual backlight voltage value?

                      Does the caps key led toggle? To confirm logic board is booting.

                      Also, this model is impacted by the Flex gate fault where the video cables are too short and get broken over time.

                      https://boards.rossmanngroup.com/thr...ning-on.61731/

                        Comment

                        • kingskie
                          Badcaps Veteran
                          • Oct 2014
                          • 249
                          • indonesia
                          #7
                          Re: 820-01987 no backlight when wake up from sleep

                          update:

                          i change Q8400 and the problem solved.

                          thanks for the help @mon2

                            Comment

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