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820-3332-A 2012 MacBook Pro, No Backlight

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  • 820-3332-A 2012 MacBook Pro, No Backlight

    820-3332-A 2012 MacBook Pro, No Backlight

    I have verified it is no backlight and not no video. Shining a light through the Apple logo, I can see an image (well the LCD is busted, so lines appear.) Video also displays correctly on an external display.

    I have measure Backlight output and I get ZERO (0)V.

    I was going over Louis' MacBook air no backlight sticky and started following that "guide".

    I have no short to ground on the line. I also couldn't initially find any break in traces from L9710 to D9701. I was looking at the voltage divider made up of R9731 and R9715 (which I actually believe are the same call-outs for the resistors on my board) and the one does measure 100ohm (99.2) and the other measures 150-180ohm (It should be 301ohm)...

    I found another 301ohm from a donor board and replaced it and when put on this board, it also measures 150-180ohm.

    The board had some liquid "damage" it did seem minimal, as I did see some around pin 32 of the LCD board connector (the LCD cable connector looks perfect), but it was just some tiny bit of blue/green oxidation.

    I am at work (however I did bring the board/computer assembly) and I can take more measurements, if would help any of you, to help me.

    **I also measured the return line resistors and I basically get 0ohm for each one, even though the schematic says they should be 10.2 ohm, can I just chalk that up to Apple Schematic being incorrect (the Air return line resistors do say they should be 0ohm)**
    Last edited by wrbailey; 10-05-2016, 01:00 PM. Reason: Return line resistors

  • #2
    Backlight output should have something to start with. Is the fuse good and is LCD_BKLT_EN present?

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    • #3
      Fuse is good. I have 11.4V on each side. LCD_BKLT_EN is not present.

      Q9706
      pin4 11.4V
      pins 1 2 5 6 0V
      pin3 11.1V

      Q9707
      pin2 3.3v
      pin3 10.78v
      pins 4 5 6 0V

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      • #4
        What creates LCD_BKLT_EN? U9100? Or does that just pass through some signals that become LCD_BKLT_EN? Like EG_BKLT_EN or IG_BKLT_EN...

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        • #5
          Did you check this with an LCD plugged in, it needs to "see" an LCD for this to work? Yes, EG_BKLT should come on and pass through U9100.

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          • #6
            Yes, the LCD is plugged in and you can see an "image" (It is cracked, so you see it come on with lines, instead of the boot Apple logo, When shining light through rear Apple Logo on LID)

            I'm looking at page 78 of my schematic "KEPLER GPIOS, CLK, & STRAPS" and it looks like it is trying to say EG_BKLT_EN is created from PP3V3_GPU_VDD33?
            I don't see how
            Last edited by wrbailey; 10-05-2016, 06:02 PM.

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            • #7
              It comes from GPU_GPIO_4, but you did not say if it is present. I assume it is not
              Check SMC_LID and IG_BKLT_EN.

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              • #8
                Smc_lid 3.4v
                ig_bklt_en 0v
                eg_bklt_en 0v

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                • #9
                  Is this thing clean enough to take to Apple? Water indicators still ok?

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                  • #10
                    There were two liquid indicators by the LCD connector that were tripped, but I could replace them with none tripped ones from another machine. I had contacted Apple initially about the graphics "recall" for these machines and they sent me a box to send it in to them. I saw you mentioned for the 2011 machines there was a cap you could remove that would cause distorted video... anything similar for this machine? I know that's shady, but, I'm assuming you don't know what my issue is or is it not fixable?

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                    • #11
                      Remove R8430 verify the boot hangs/corrupted video on external LCD and then take it to Apple.

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                      • #12
                        It's got a cracked LCD... still think they'll replace the board?

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                        • #13
                          So are you not sure what the issue could be?

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                          • #14
                            Just get another LCD the take it to Apple. I have no idea what it could be, why fuck with it if Apple will fix it for free?

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