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820-3115 does not turn on when LVDS cable plugged in

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  • 820-3115 does not turn on when LVDS cable plugged in


    I bought this shit from craigslist.
    The lady said she spilled some water on the macbook.
    She heard some sizzling and she couldn't turn it back on anymore.

    The macbook is in a pristine condition.
    I took it apart and I couldn't find where the water was spilled.
    No corrosion on the board. Maybe a little corrosion on C3897,

    I cleaned the whole board. After I dried it I attached the power cable and it turned on.
    I attached the speaker and I heard the dong sound. I put it back to the macbook and it didn't turn on.
    I disconnected all the cable except the LVDS cable. It still didn't power on. After I removed the LVDS cable it turned on.
    I tried with a different LCD same thing. I replaced the LVDS connector. Still nothing. It won't even try to turn on.
    It doesn't do anything. Fan is not spinning. Nothing at all.

    I pulled the backlight fuse. I thought maybe something with the backlight circuit. No luck.
    I pulled
    L9004 and it turns on. Has backlight, but of course no picture. I checked everything for short or low resistance.
    I replaced L9004 and U9000. These didn't solve anything.
    I pulled C9011 and C9012 and C9015. Same shit.
    I pulled U9000 again and solder a wire from Pin 2,3 to Pin 4,5. The 3.3V rail is jumping up and down and it does not turn on.
    I know my test LCD is good. I just used it yesterday. Anyway I would believe something is wrong with the LCD.

    Any thoughts?

    Last edited by bighead; 04-23-2016, 07:01 AM.

  • #2
    Did you check L9004 for shorts with the LCD plugged in?


    • #3
      Yes, I did. That was the first thing I did. No short on L9004.
      5K range when LCD plugged in.
      Last edited by bighead; 04-23-2016, 09:39 PM.


      • #4
        I removed L9004 and attached my bench PSU on pin2.

        It draws 0.21xxA when the macbook is turned off.
        When it turns on it draws 0.23xxA and have picture.
        WTF should I do with this macbook?


        • #5
          So if the LCD is plugged in it will not even spin the fan, totally dead? This makes no sense because nothing should happen on L9004 until U9000 is switched on, this will only happen after the dong and the LCD is recognized. Is there 3V on L9004 immediately after you apply power?


          • #6
            No, the fan won't even spin if the LCD connected. Totally dead. Nothing on L9004 when I apply power.
            Looks like it has a problem with the PP3V3_S5 rail. When I try to turn it on when LCD connected the PP3V3_S5 collapse.


            • #7
              I changed the TPS51125 and now everything is working fine. Problem solved. Thanks for your help!


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