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820-01598 stuck at 20V 0.175A

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    #1

    820-01598 stuck at 20V 0.175A

    I´m working on a a2159 which doesn´t start anymore. It is stuck at 20v@0.175A. All_SYS_PWRGD is present. PM_PCH_SYS_PWROK is also present. CPU gets warm. I also get some fan spin, but nothing else happens.

    No waterdamage, board looks very clean.


    Not sure what to check next. Any suggestions?
    Tags: None
    #2
    Re: 820-01598 stuck at 20V 0.175A

    Review this power on sequence for this logic board:

    https://drive.google.com/file/d/1oBr...SjpQfYbKq/view

    Attempt a DFU.

    Comment

      #3
      Re: 820-01598 stuck at 20V 0.175A

      DFU restore and revive didn´t change anything.

      I also checked the power on sequence diagram. PM_PCH_SYS_PWROK is the last entry. So if this signal is present, everything else during power on sequence should also be fine, right?


      My guess would be a CPU related problem, but I don´t know how to check if CPU is working fine

      Comment

        #4
        Re: 820-01598 stuck at 20V 0.175A

        I nailed it down to PPVDD_S0_CPU not being present. Measuring 4Ohm which looks good compared to other board.


        I also took a closer look at U7100 and U7210/7220 which are creating this rail:

        PP5V_COREVR_VCC: 5,1V
        PPVIN_S0_CPUVR_VIN: 12,63V
        CPU_VR_READY: 0V
        CPU_VR_EN_R: 1.8V
        CPUSA_FCCM: 2,5V for first 5 seconds, than going to 5V
        PPBUS_HS_CPU: 12,63V
        PP5V_G3S_CPUREG_MISC: 5,1V
        CPUCORE_FCCM: 2,5V for first 5 seconds, than going to 0V
        CPUCORE_PWM1: 2,5V
        CPUCORE_BOOT1: 4,79V

        PPVCCSA_S0_CPU is 1.05V and must be present before PPVDD_S0_CPU shows up, so that should be OK.

        I think U7210 needs both CPUCORE_FCCM AND CPUCORE_PWM to be present in order to create PPVDD_S0_CPU, right?

        Any Idea what´s the problem is and how to move on?

        Comment

          #5
          Re: 820-01598 stuck at 20V 0.175A

          There´s a mistake in my last post --> Must be PPVCC_S0_CPU instead of PPVDD_S0_CPU of course..


          Any Idea what to check next?

          Comment

            #6
            Re: 820-01598 stuck at 20V 0.175A

            Check the enable pin voltage to ground of PPVCC_S0_CPU regulator.

            Comment

              #7
              Re: 820-01598 stuck at 20V 0.175A

              CPU_VR_EN_R: 1.8V

              That´s the only enable pin I can find on U7100. Please correct me if it´s not the right one I´m looking at..

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