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820-3432 no lcd

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  • 820-3432 no lcd

    It appear I need to replace c8312 as I am getting no voltage from it and it looks a bit ugly. However in an attempt to replace it I have misplaced the little bugger on my trash board, how would I go about finding equivalent caps on the trash board I have? Or would I need to buy a new trash board from aliexpress.

    Thanks.

    Capture.PNG

  • #2
    It works fine without. Also no idea what a 820-3432 is

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    • #3
      Thanks for the promp reply Duke.
      820-3432 is the name of the brd file on the mid 2013 macbook air. I don't know what it is either. So the c8312 chip is not required and I should remove it instead of replacing it?

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      • #4
        As long as it is not shorted it will not affect operation.

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        • #5
          U8300 pins 2&3 are 3.3v; nothing on pins 4 & 5
          C8309 is 3.3v
          C8311 is 0
          C8312 is removed

          I have replaced U8300 and still getting the same results

          Any ideas what to test next?

          Thanks in advance

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          • #6
            Does this thing even chime? Did you try a known good LCD assembly? Is SMC_LID high?

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            • #7
              chime and green light. Will test SMC_LID high to morrow and get back to you.

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              • #8
                So before I took it apart it had chime and green light.
                Now no chime and no green light

                I took the following measurements from U7090:

                1) 0.58
                2) 0.1
                3) 128.33
                4) 127
                5)gnd
                6) 17.77
                7)NC
                8) 17.77

                Pin 4 was shorting to ground. Replaced U7090, and tested it for shots to ground before powering it on. Now after powering it on the I am getting a short to ground on pin 4.

                The numbers I am getting are obviously so far wrong I don't know what to do. This is my first board I have tried to fix so please don't abuse me too much duke...

                Last edited by oneoone; 12-18-2016, 11:33 PM.

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                • #9
                  I have no idea what you are doing or why you are messing with U7090. Is 3V42 present?

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                  • #10
                    3v42 is not present neither is ppbus g3h

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                    • #11
                      Is there a short to GND on 3V42?

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                      • #12
                        3v42 reads 0.1v. Testing in continuity mode suguests it is shorted to ground. Is this where I should be focusing my research?

                        EDIT: I am about to remove L7095 and test for a short either side as per Louis instructions here: How does PP3V42_G3H circuit work and does it require PPBUS_G3H to operate?

                        EDIT2: short to ground still exists on bottom pad. Are there any tips to finding what is shorting it to ground or should i just start pulling up everything one by one until the short is gone?
                        Last edited by oneoone; 12-19-2016, 09:40 PM.

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                        • #13
                          Inject voltage and see what heats up, start low at 1V and see how much current it draws and go up from there. You fried this board.....

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                          • #14
                            I 100% fried the board. Is it salvageable? Where is the best place to learn how to not fry boards or is it just experience?

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                            • #15
                              I also don't have a working power meter, so looks like I am going on a bit of an expedition unless you have a solution?

                              Thanks

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