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MacBook Air 2011 13" >820-3023 A< no power (PLT_RESET_L missing)

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    MacBook Air 2011 13" >820-3023 A< no power (PLT_RESET_L missing)

    Dear community,
    this is my very first post, I am quite new to macbook repairs, and I am excited:-)

    I have a 2011 MacBook Air 13' that does not power on. No fan spin, nothing.

    Here are the specs:

    MacBook Air Mid-2011
    CPU: 1.7 GHz Core i5 (I5-2557M)
    Model: A1369 (EMC 2469)
    RAM: 4 GB
    VRAM: 384 MB


    The first question:
    Unfortunately, it came with a 'fake' power adapter which seems not to talk to the computer. Sometimes it does show green light immediately after connecting it to the board, sometimes it shows green light after a few seconds, sometimes it doesnt show a green light at all. But it has never shown red light.. I thought that the DC-IO-Board may be faulty, but I tried with another DC-IO-Board from another Macbook Air with the same specs - still nothing. The second Macbook Air has the 3-beep-fault, but at least it has a fan spin. Due to this, I assume that its DC-IO-board is good. Hence, I assume that the first Macbooks IO-Board is okay, too.
    I do have an original MagSafe from 2011, but it is the one for the Macbook Pro, giving 16.5 V/3.65 A. Can I use this one on my Macbook Air to test? On the Air's cover there are 14.5 V/3.1 A specified only.


    The second question:
    PPBUS_G3H = 8.36 V

    According to the schematics, it should be 12.8 V, but the other Macbook with the 3-beep-failure also has 8.36 V on PPBus_G3H. Can I assume PPBus_G3H to be okay then?

    Third question:
    While measuring some rails, I noticed:
    PPVIN_SW_T29BST = 0.14 V
    But in the Rossmann forum I have read that this has to do with thunderbolt, hence I assume that I dont have to care about this right now.

    Fourth question:
    I also noticed:
    CPU_RESET_L = 0.14 V
    On the other board this was 1 V. CPU_RESET_L is made by U2780 with:

    PP3V3_S0_RSTBUF = 3.3 V
    PLT_RESET_L = 0.0 V

    ..C2680 and R2680 are not shorted to ground.

    PLT_RESET_L is sent out from the PCH, hence I wanted to check if the PCH is powered on:
    PP3V3_S5_PCH_VCCDSW= 3.3 v
    PPVRTC_G3_PCH = 3.3 v
    PP1V05_S0_PCH_VCC_CORE = 1.05
    PM_SLP_S5_L = 3.34 v

    This seems good. Hence, I assume that U2780 is broken.


    :::Some other rails that I measured:

    PPBUS_S0_LCDBKL = 8,36 V
    PPBUS_S0_VSENSE = 8,36 V
    PPVIN_S5_P5VP3V3 = 3,3 V
    PP18V5_DCIN_CONN = 14,86 V (strange?!.., as with PPBus_3GH)
    PPDCIN_OR_PBUS = 14,86 V
    PPDCIN_G3H_INRUSH = 14,86 V
    PP3V42_G3H_REG = 3,42 V
    PP3V3_S5_LPCPLUS = 3,3 V
    PP3V3_S5_SMC = 3,3 V
    PP3V42_G3H_CHGR = 3,42 V
    PP3V42_G3H_PWRCTL = 3,42 V
    PP3V42_G3H_SMBUS_SMC_BSA = 3,42 V
    PP3V42_G3H_ONEWIRE = 3,42 V

    PP5V_S0_FET = 5 V
    PP5V_S0 = 5 V
    PP5V_S0_BKL = 5V

    PP3V3_S5_REG = 3,3 V
    PP3V3_S5_XDP = 3,3 V
    PP3V3_S5_CPU_VCCDDR = 3,3 V
    PP3V3_S5_LCD = 3,3 V
    PP3V3_S5_PCH = 3,3 V
    PP3V3_S5_PCHPWRGD = 3,3 V
    PP3V3_S5_SYSCLK = 3,3 V
    PP3V3_S5_VMON = 3,3 V
    PP3V3_S5_PWRCTL = 3,3 V
    PP3V3_S5_PCH_VCC_SPI = 3,3 V
    PP3V3_S5_P3V3SUSFET = 3,3 V


    I am very thankful for any help:-)

    #2
    Re: MacBook Air 2011 13" &gt;820-3023 A&lt; no power (PLT_RESET_L missing)

    45W, 60W and 85W Magsafe will work without issue on MacBook Air.
    PPBUS_G3H is always 8.xV on MacBook Air (8.4V for 2012 and older). 12.6V is for most Pro. Don't trust voltage indication on schematics.

    As always you have to go through the list of power rails and check what's present and what's missing. No point in listing multiple names of the same power rail.
    OpenBoardView — https://github.com/OpenBoardView/OpenBoardView

    Comment


      #3
      Re: MacBook Air 2011 13" &gt;820-3023 A&lt; no power (PLT_RESET_L missing)

      Originally posted by piernov View Post
      45W, 60W and 85W Magsafe will work without issue on MacBook Air.
      PPBUS_G3H is always 8.xV on MacBook Air (8.4V for 2012 and older). 12.6V is for most Pro. Don't trust voltage indication on schematics.
      Thanks for that hint!


      Originally posted by piernov View Post
      As always you have to go through the list of power rails and check what's present and what's missing. No point in listing multiple names of the same power rail.
      Ah okay, so you mean it is unnecessary to measure the subrails? For example there's no need to measure PPBus_S0_LCDBKLT when I have already measured PPBus_G3H because they are actually the same rail and the same voltage?!

      Comment


        #4
        Re: MacBook Air 2011 13" &gt;820-3023 A&lt; no power (PLT_RESET_L missing)

        Update:

        I spent some more time with the board and I noticed that ALL_SYS_PWRGD is not present. I measured the necessary rails and I found out that PPDDR_S3_REG is shorted to ground. Then, I took a look around the area where PPDDR_S3_REG is built and I saw that it is a little bit wet around C7341 and C160Z. Attached you see two pictures of this area, one of the faulty board and one of my comparison board. What do you think? Also, what would be the best method to find the location of the short? Voltage injection? Unfortunately, I dont have a laboratory power supply yet..


        Last edited by _Cupa; 04-02-2021, 10:32 AM. Reason: image upload failed

        Comment


          #5
          Re: MacBook Air 2011 13" &gt;820-3023 A&lt; no power (PLT_RESET_L missing)

          Update:
          I measured the remaining main power rails and there is quite something not right:
          PP3V3_S5 = 3,3 V
          PP3V3_SUS = 3,3 V
          PP3V3_S3 = 3,3 V
          PP3V3_S0 = 3,3 V
          PP1V8_S0 = 1,78 V
          PP1V5_S3 = 0 V shorted to GND
          PP1V5_S3RS0 = 0,27 V Resistance to Gnd = 127 Ohm
          PP1V5_S0 = 1,5 V
          PPVTTDDR_S3 = 0 V , shorted to GND
          PP0V75_S0_DDRVTT = 0 V, shorted to GND
          PPVCCSA_S0_CPU = 0,88 V, seems ok, specified as 0.9 V
          PP1V05_SUS = 1,05 V
          PP1V05_S0 = 1,05 V
          PP15V_T29 = 0,21 V, on the other board 0,16 V
          PP3V3_T29 = 2,44 V, on the other board 3.3 V
          PP1V05_T29 = 0,04 V on the other board 1,03 V
          PP1V05_S0_PCH_VCCADPLL = 1,05 V
          PPVCORE_S0_CPU = 0,0 V Resistance to Ground = 25 Ohms (on the other board 1,17 V and also 25 Ohms)
          PPVCORE_S0_AXG = 0,0 V Resistance to Ground = 17 Ohms (on the other board 0,0 V and 26 Ohms
          PP1V5_S3_CPU_VCCDQ = 0,28 V Res to Gnd 123 Ohms = (on the other board 1,49 V and 163 Ohms)
          PP1V05_S0_CPU_VCCPQE = 1,05 V
          PP1V8_S0_CPU_VCCPLL_R = 1,78 V

          Comment


            #6
            Re: MacBook Air 2011 13" &gt;820-3023 A&lt; no power (PLT_RESET_L missing)

            Did someone attempt to reflow the RAM?
            OpenBoardView — https://github.com/OpenBoardView/OpenBoardView

            Comment


              #7
              Re: MacBook Air 2011 13" &gt;820-3023 A&lt; no power (PLT_RESET_L missing)

              Originally posted by piernov View Post
              Did someone attempt to reflow the RAM?
              I don't think so, the RAM chips look very clean and their surrounding, too.

              Comment


                #8
                Re: MacBook Air 2011 13" &gt;820-3023 A&lt; no power (PLT_RESET_L missing)

                Does someone have an idea in which of the missing power rails i should investigate time next?

                Comment


                  #9
                  Re: MacBook Air 2011 13" &gt;820-3023 A&lt; no power (PLT_RESET_L missing)

                  If PP1V5_S3, PP0V75_S0_DDRVTT and PPVTTDDR_S3 are all fully shorted to ground, the culprit is most likely U7300.
                  OpenBoardView — https://github.com/OpenBoardView/OpenBoardView

                  Comment


                    #10
                    Re: MacBook Air 2011 13" &gt;820-3023 A&lt; no power (PLT_RESET_L missing)

                    Originally posted by piernov View Post
                    If PP1V5_S3, PP0V75_S0_DDRVTT and PPVTTDDR_S3 are all fully shorted to ground, the culprit is most likely U7300.
                    Thank you for that advice. I will spend some time with the schematic and the area around U7300 and then I need to exercise a bit with the hot air station. I got mine just a few days ago and I should exercise with an old board before I try to do real stuff. I will get back to this thread when Im done:-)

                    Comment


                      #11
                      Re: MacBook Air 2011 13" &gt;820-3023 A&lt; no power (PLT_RESET_L missing)

                      Hi i have this same Macbook Air and i am in need of the schematics for the 820-3023-A board! If you can help me it would be much appreciated.......Thanks

                      Comment


                        #12
                        Re: MacBook Air 2011 13" &gt;820-3023 A&lt; no power (PLT_RESET_L missing)

                        https://www.badcaps.net/forum/showth...ght=820-3023-A

                        Comment


                          #13
                          Re: MacBook Air 2011 13" &gt;820-3023 A&lt; no power (PLT_RESET_L missing)

                          Thanks for the link mon2 Take care!

                          Comment

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