Macbook Pro A1502 820-4924A BACKLIGHT ISSUE

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  • Instafixx
    Badcaps Veteran
    • Jul 2022
    • 374
    • India
    #1

    Macbook Pro A1502 820-4924A BACKLIGHT ISSUE

    Hello,
    i have a Macbook A1502 with No Backlight but the image is on as confirmed by a flashlight.

    the macbook was dirty so i went ahead and cleaned it. the light back on for a couple of minutes and now its again back off.

    The resistance of the Pins at j8300 look okay as confirmed by tallying from a donor board.

    I think its a mosfet issue with the Q7701 but never quite understood how these things work.
    Can anyone guide?
    Tags: None
    • Instafixx
      Badcaps Veteran
      • Jul 2022
      • 374
      • India
      #2
      Re: Macbook Pro A1502 820-4924A BACKLIGHT ISSUE

      Update : Did and SMC Reset, have Backlight for 1 second then it went away !

        Comment

        • Instafixx
          Badcaps Veteran
          • Jul 2022
          • 374
          • India
          #3
          Re: Macbook Pro A1502 820-4924A BACKLIGHT ISSUE

          Originally posted by Instafixx
          Update : Did and SMC Reset, have Backlight for 1 second then it went away !
          Interesting development while checking the LCD Connector Voltages is that when when we touch the meter probe to Point 15 the Lcd starts working normally .

          To confirm I ran a jumper wire from point 15 to point 16 of J8300 and the LCD starts working normally. I think I just bypassed some circuit or mosfet. Would like to do a full proof solution to this so if anyone here can help would be highly obliged.

          Thanks In Advance.

            Comment

            • mon2
              Badcaps Legend
              • Dec 2019
              • 14039
              • Canada
              #4
              Re: Macbook Pro A1502 820-4924A BACKLIGHT ISSUE

              Can you post a clear pic of the points on J8300 you have bridged?

              Review the j8300 connector using the boardview file. What are the labels on the pins that you have bridged?

              From the schematic, pin 15 is the negative phase of the data lane 0 for this display. Pin 16 is ground. Need to review exactly which pins you are referencing.

                Comment

                • Instafixx
                  Badcaps Veteran
                  • Jul 2022
                  • 374
                  • India
                  #5
                  Re: Macbook Pro A1502 820-4924A BACKLIGHT ISSUE

                  Originally posted by mon2
                  Can you post a clear pic of the points on J8300 you have bridged?

                  Review the j8300 connector using the boardview file. What are the labels on the pins that you have bridged?

                  From the schematic, pin 15 is the negative phase of the data lane 0 for this display. Pin 16 is ground. Need to review exactly which pins you are referencing.
                  Yes Pin 15 is DP_INT_ML_N<0>.
                  and Pin 16 is Ground.

                  So as i said i was just checking the voltage of the Pins of J8300 with the Macbook on and the battery and display plugged in and when we touch the Pin # 15 the screen comes ON.

                  Even when there is no probe on the ground still the screen used to come ON. Hence making a jumper from 15 to 16 did the trick.

                    Comment

                    • mon2
                      Badcaps Legend
                      • Dec 2019
                      • 14039
                      • Canada
                      #6
                      Re: Macbook Pro A1502 820-4924A BACKLIGHT ISSUE

                      Very strange as this is the data line for the display contents. If you are able to see the expected graphics on the LCD screen, then this data line is working.

                      Perhaps you are allowing for a ground connection and completing the circuit to permit the backlight boosted voltage to be on.

                        Comment

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