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Macbook Air A1466, 820-3437 S0 present but doesn't turn on

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    #1

    Macbook Air A1466, 820-3437 S0 present but doesn't turn on

    Hello,

    First time doing a macbook board (board no. 820-3437-B), and the architecture is completely new and different to me from regular laptops. I'm stumped. Measured a bunch of stuff already and don't know where to go next.

    When plugging in charger the light goes green then orange, fan does not start. Current draw is 0.1A constantly.

    Heres what I measured so far:

    PPBUS_G3H - 8.5V
    SMC_RESET_L - 3.4V
    PM_SLP_S3_L - 3.3V
    PM_SLP_S4_L - 3.3V
    PP3V3_S5 - 3.3V
    PP1V05_S0 - 1.05V
    P1V8S_PGOOD - 0V
    P5VS4RS3_PGOOD - 0V
    P1V05S0_PGOOD - 0V
    DDRREG_PGOOD - 0V
    PP3V3_S0 - 3.3V
    PP1V5_S0 - 1.5V
    PP5V_S0 - 5.1V

    Any ideas where to go with this next? No visible liquid or physical damage.
    Last edited by FrozenHaxor; 07-31-2019, 10:21 AM.
    Tags: None
    #2
    Re: Macbook Air A1466, 820-3437 S0 present but doesn't turn on

    Missing ALL_SYS_PWRGD. So missing rail most likely.
    PP1V8_S3, PP1V2_S3… others seem present.
    OpenBoardView — https://github.com/OpenBoardView/OpenBoardView

    Comment

      #3
      Re: Macbook Air A1466, 820-3437 S0 present but doesn't turn on

      Originally posted by piernov View Post
      Missing ALL_SYS_PWRGD. So missing rail most likely.
      PP1V8_S3, PP1V2_S3… others seem present.
      Well the CPU rail is definitely not there. Apparently a release of magic smoke was involved when the Macbook died, doesn't appear that anything has a hole in it. Investigating CPU rail now.

      Comment

        #4
        Re: Macbook Air A1466, 820-3437 S0 present but doesn't turn on

        CPU VCore won't be present without ALL_SYS_PWRGD.
        OpenBoardView — https://github.com/OpenBoardView/OpenBoardView

        Comment

          #5
          Re: Macbook Air A1466, 820-3437 S0 present but doesn't turn on

          Measured all PGOOD sources. Looks like the only one missing is the DDRREG_PGOOD.
          No voltage on L7430. Should that be on at this point?

          ----

          DDRREG_EN goes to 3.3V so I assume it should go on at this point.
          Last edited by FrozenHaxor; 07-31-2019, 11:42 AM.

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            #6
            Re: Macbook Air A1466, 820-3437 S0 present but doesn't turn on

            I think U7400 has a hole in it, doesn't seem right. Will investigate more.
            Attached Files

            Comment

              #7
              Re: Macbook Air A1466, 820-3437 S0 present but doesn't turn on

              If you're missing PP1V2_S3, that's indeed an issue. Measure resistance to ground on that line.
              I don't see anything wrong with this chip, although it could still be the culprit if there's no short to ground.
              OpenBoardView — https://github.com/OpenBoardView/OpenBoardView

              Comment

                #8
                Re: Macbook Air A1466, 820-3437 S0 present but doesn't turn on

                L7430 to ground is about 1.3kOhm.

                Comment

                  #9
                  Re: Macbook Air A1466, 820-3437 S0 present but doesn't turn on

                  Ok, so on U7400, you get 5V on pin 12, 3.3V on pin 16, but nothing on pin 13? And no short to ground?
                  Looks like U7400 itself is bad then. There are a few passive components around it, but it seems like there is no damage around the IC so it's unlikely that they are bad.
                  OpenBoardView — https://github.com/OpenBoardView/OpenBoardView

                  Comment

                    #10
                    Re: Macbook Air A1466, 820-3437 S0 present but doesn't turn on

                    That is correct. Just replaced U7400 with brand new one, and it behaves in exactly the same way as the old one did. Perhaps the inductor driver is bad? I do not detect a short to upper rail nor to ground on those integrated mosfets, gates do not appear to be shorted either. This is very odd. Sadly I cannot swap CSD58873Q3D with another one on this board since the other two appear to produce 5V and 3.3V rails which are needed for the 1.2V rail to work. It could prove though that the 1.2V rail one is operational if I swap it in place of the 3.3V one. I also seem unable to buy that part in my country.


                    ------

                    Swapped Q7430 with Q7520 - the result is that 5V rail is still good and the 1.2V rail still doesn't work, so the CSD58873Q3D from 1.2V circuit is good.

                    Measured all passives around U7400 - all checks out according to schematic.
                    Last edited by FrozenHaxor; 08-03-2019, 05:32 AM.

                    Comment

                      #11
                      Re: Macbook Air A1466, 820-3437 S0 present but doesn't turn on

                      Hum… not sure, except if the new U7400 was bad as well, but it's not common for it to fail anyway…
                      Measure voltage and resistance to ground on PP0V6_S0_DDRVTT and PPVTT_S3_DDR_BUF as well. And voltage on MEMVTT_PWR_EN and DDRREG_1V8_VREF. Maybe it'll give a hint.
                      OpenBoardView — https://github.com/OpenBoardView/OpenBoardView

                      Comment

                        #12
                        Re: Macbook Air A1466, 820-3437 S0 present but doesn't turn on

                        Here are the measurements:

                        PP0V6_S0_DDRVTT - 0V, 0.62kOhm to ground
                        PPVTT_S3_DDR_BUF - 0V, 2.47kOhm to ground
                        MEMVTT_PWR_EN - 3.22V
                        DDRREG_1V8_VREF - 1.8V

                        Comment

                          #13
                          Re: Macbook Air A1466, 820-3437 S0 present but doesn't turn on

                          No idea, those look normal for the current situation.
                          Make sure there's no corrosion at all, especially on DDRREG_VBST_RC, and no components were knocked off the board around U7400.

                          Also check resistance across R7450 to make sure it's close to 0 ohm.
                          OpenBoardView — https://github.com/OpenBoardView/OpenBoardView

                          Comment

                            #14
                            Re: Macbook Air A1466, 820-3437 S0 present but doesn't turn on

                            It is really odd indeed, like everything is okay but the IC does not start. I will put the board through ultrasonics. It has been in another shop afterall and they had a go at it giving up in the end - who knows what they did, no soldering signs only probing marks. When taking the shields off I noticed slight staining like dried water, perhaps it had some liquid damage before and they did not take shields off for cleaning leaving some residue - or its factory like that. I genuinely do not see any damage or etching myself. Will see after the ultrasonic cycle, tank is heating up.


                            ------

                            Still no change after thorough cleaning. Board is spotless.

                            R7450 is 0.01Ohm
                            Last edited by FrozenHaxor; 08-05-2019, 05:50 AM.

                            Comment

                              #15
                              Re: Macbook Air A1466, 820-3437 S0 present but doesn't turn on

                              The board was replaced. Sometimes you just have to give up in order to not waste too much precious time. Thanks for trying to help me solve this puzzle though

                              Comment

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