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2019 macbook a2141 backlight troubleshooting

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    2019 macbook a2141 backlight troubleshooting

    Hello, I have a 2019 macbook a2141 with no backlight. video image is visible with flashlight but no backlight. All the associated circuitry is located on the back side of the logic board. I've removed the logic board and display and have them connected together on the bench so I can probe the back side of the board. I'm applying power through a usb-c port attached to the logic board but I'm not sure how to actually boot the logic board. I tried attaching the power button and that didn't work. I also have the fans attached and they are not spinning. If anyone can help me with this setup I would certainly appreciate it. Thank you.

    #2
    Re: 2019 macbook a2141 backlight troubleshooting

    See attached -> locate one of the 2 power buttons that should be a low profile surface mounted pushbutton.

    Press it and confirm that you can see the display graphics without the backlight.

    Then carefully confirm the voltage to ground of:

    ISNS_LCDBKLT_P
    ISNS_LCDBKLT_N
    BKLT_EN_R
    PPVOUT_S0_LCDBKLT


    Is your keyboard backlight working? The same backlight controller on this model appears to drive the LCD and the keyboard backlights.

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      #3
      Re: 2019 macbook a2141 backlight troubleshooting

      Hi mon2, I didn't see an attachment. I did not realize there were surface-mounted pushbuttons on the logic board. I will look for them. This could help me greatly. I don't know if the keyboard backlight is working because it may have been disabled. I received this macbook not working. Thank you!

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        #4
        Re: 2019 macbook a2141 backlight troubleshooting

        Further information - I do not have PPVOUT_S0_LCDBKLT voltage - should read 59V, I read 0V. Also do not have EDP_BKLT_EN. And furthermore, BKLT_SD reads 12.5V (should read 0V to turn on Q8400 to pass 12.6V to backlight boost).

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          #5
          Re: 2019 macbook a2141 backlight troubleshooting

          I knew I forgot something...
          Attached Files

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            #6
            Re: 2019 macbook a2141 backlight troubleshooting

            Thank you! I had not seen these!

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              #7
              Re: 2019 macbook a2141 backlight troubleshooting

              Tried the onboard pwr button (actually these was no switch, just two pads) to no avail. I cannot seem to get the logic board to boot on the bench. If anyone has successfully booted an a2141 logic board out of the case please let me know the setup. Maybe I should have done an NVRAM reset and/or SMC reset before disconnecting the board (?). Although without a battery connection it seems the NVRAM would reset on pwr up.

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