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820-4924 Orange light, missing ALL_SYS_PWRGD

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  • 820-4924 Orange light, missing ALL_SYS_PWRGD

    820-4924 came in with no signs of liquid damage and no power on and no mag light. I left the board alone for 2 days while I worked on other repairs, and by the time I got to the board, I first plugged in magsafe and got a orange light. Light disappeared after a few seconds. I then removed magsafe and battery and held power button down for 10 seconds, reconnected power and got orange light and was able to boot machine to login screen. I decided to leave machine alone to charge up battery and noticed mage safe disappeared after a few minutes.

    Now device has orange light, and no boot. First thing I checked was All_SYS_PWRGD and noticed it was not present.

    PP3v42= 3.42v
    PPBUS = 12.6v
    PPVRTC_G3= 3.V
    PPVIN_S5= 12

    PP5V_S5 = 5V
    PP5V_S4 = 0
    PP3V3_S5= 3.3V
    PP3V3_S4= 0

    It appears my PM_SLP_S5_L is not present so S4, S3, S0 rails are not present. Checked up the line and found PM_SLP_S5_L is created by U0500, so I looked into PM_PCH_PWROK and noticed it wasn't present either. I then noticed that PM_PCH_PWROK is created by the U1950 Logic Gate, which is enabled once ALL_SYS_PWRGD is present.

    I feel like I just went in a giant circle and was hoping for any advice on what I should be looking at next.

    Thank you in advance.





  • #2
    Whoops, Did not mean to put PPVIN_S5=12. Apparently made up a reading.

    Comment


    • #3
      ALL_SYS_PWRGD will only appear after all secondary voltages are generated; les CPU one.
      If board booted in SMC bypass, this means a SMC sensor issue.
      Does it still start in this mode?
      If yes, start checking VD0R, VP0R, IP0R and IPBR output sensors.

      Comment


      • #4
        Thank you for clarifying that for me. I had a feeling that is what I was dealing with, but I wasn't sure. Okay so I tried the SMC bypass and the board pulls 0.200 Amps from DCPS. Power rails are being pulled down.

        PP5V_S5=5v
        PP5V_S4 = 4.8v
        PP5V_S3 = 2.35v
        PP5V_S0 = 2.3v
        PP3V3_S5 = 3v
        PP3V3_S4 = 3V
        PP3V3_S3 = 3V
        PP3V3_S0 = 3v
        PP1V5_S0 = 1.5v


        Since device is not booting all the way with SMC Bypass, I believe I need to resolve whatever is pulling PP5V down first before looking into SMC Sensor.

        Comment


        • #5
          You MUST check the SMC sensor involved in power sequence.
          Because is the reason board doesn't even start the sequence...

          "PP5V_S3 = 2.35v"
          I suppose measured on SMC bypass mode.
          In normal mode do you catch a pulse there, at least?
          Try triggering SMC_ONOFF_L.
          If yes, son't need to check above mentioned sensor (previous post).

          Seems to have a problem with 5V_S3 power rail.
          Post resistance to ground at L7520.

          Comment


          • #6
            Yes, PP5V_S3 = 2.35V in SMC Bypass mode.
            In normal mode, there is no pulse, even after triggering SMC_ONOFF_L
            L7520 Diode Reading= 0.392v

            All measured in normal mode
            VD0R = 2.4v
            VP0R = 0v
            IP0R = 0.034v
            IPBR = 0.063v

            Comment


            • #7
              Try to solve 5V_S3 problem starting in bypass mode.
              Check R7520-22, C7524 and R7544.
              Post exact value for P5VS3_EN.

              Comment


              • #8
                R7520, R7521, R7522, R7544 are all measuring correct resistance. C7524 is not shorted.
                R7520, R7522= 2.35v
                P5VS3_EN = 2.9v

                Comment


                • #9
                  Then change U7501...

                  Comment


                  • #10
                    Sorry for the long delay. I did not have access to post on the forum for some reason, but I am back on now. I replaced U7501 and now the board will power on in SMC bypass mode will all rails present for a second then turn off, then power back on again after a few seconds, then power off again. I checked the current sensing resistors on ISL6925 and I am getting 21 ohms between Pins 27 and 28 on U7100, which seems normal, and 4 ohms between Pins 17 and 18.

                    Without smc bypass, PM_SLP_S4_L is missing. I am currently looking into the VRTC, BIOS and SMC sensors. Any other suggestions on what I should be looking into?

                    Thank you

                    Comment


                    • #11
                      You should check SMC voltage sensors, if no pulse at all at PM_SLP_S4_L.
                      Start with VP0R and VD0R.

                      Comment


                      • #12
                        Thanks. I am looking into to that now. I did make a discovery and noticed there was an issue with my MagSafe 2 cable that I have plugged into my DCPS. I replaced the MagSafe 2 cable and now I draw .025A upon connecting to board and spike to .400A for a split second, and drop back to .025A.

                        With new MagSafe cable connected, I get 3.3v on PM_SLP_S4_L for a split second.
                        Split second pulse of 3.3v on PM_SLP_S3_L when connected.

                        Will report back after looking into SMC voltage sensors.

                        Comment


                        • #13
                          If you get pulse even on PM_SLP_S3_L, then check all I/V sensors, not only VD0R and VP0R...

                          Comment

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