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820-3437 unstable PPVRTC_G3H and SMC_PM_G2_EN

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  • 820-3437 unstable PPVRTC_G3H and SMC_PM_G2_EN

    No signs of liquid damage on this board or machine at all. Doesn't appear to have been cleaned previously.
    Sometimes I get a short (5 seconds or so) fanspin out of the board and the CPU heats up but it's sporadic and nothing sustained.

    Green light so one wire is working
    PP5V_S5 - multimeter (fluke) goes crazy get lightning bolt icon indicates 3.4v-34.4v not seen this before
    PPVRTC_G3H switching between 3.25 and 3.41v
    SMC_PM_G2_EN unstable 0 to 3.41 bouncing about every half a second.
    audible faint ticking corresponding with the power fluctuation near the U2800 area (I think) unhooked the fan and it still faintly clicks.

    R8000,8011,8050,8020 not shorted to ground
    PP3V S5, S4RS3, S3, S0 not shorted to ground
    PP5V S5, S3, S0 not shorted to ground

    Tried reflowing (or rehotting as Louis was joking the other day) the SMC, no change.
    I'm a bit stuck at this point. Any ideas?
    Last edited by aarone; 05-04-2017, 11:19 AM.

  • #2
    PPBUS voltage? Seeing any activity on L7520 or L7560?


    • #3
      PPBUS_G3H varies a little between 8.58 and 8.65 on R7006, doing the same fluctuating on both sides of F7140
      L7520 shows a the - sign flashing on and off and a small number of volts like .005v fluctuating
      L7560 is cycling from 0 to 3.3 or so volts


      • #4
        Voltage on PP3V42_G3H??


        • #5
          Originally posted by aprendiz View Post
          Voltage on PP3V42_G3H??
          A steady 3.42 V on L7095.


          • #6
            Inspect corrosion in U6100 U1900 area and pin8 of U1950. If that is all good, this board is gonna suck. Could really be anything.


            • #7
              Yeah no corrosion anywhere unfortunately. Looking at the schematic could a faulty ISL6259 cause improper signaling to Q7130 (which looks like it creates PPBUS_G3H) and that cause the fluctuations on PPBUS_G3H? Is there anyway to meter CHGR_LGATE and CHGR_UGATE to know if the ISL6259 is working properly to communicate to Q7130 how long to pulse to make PPBUS_G3H?

              Using a different charger (both are OEM) I get about an 11 second fan spin, then off and then on for a split second and then off again permanently.
              Last edited by aarone; 05-04-2017, 06:27 PM.


              • #8
                Is the 10 seconds fan spin then off always happening or is it random at times?


                • #9
                  it's random unfortunately. Sometimes it does it right away when the charger is connected and sometimes it doesn't :/

                  It wasn't doing it and I pressed down on the U7200 area and it started doing it. No idea if that means anything for real or if it's a red herring.

                  10 sec on, one off, small blip... then about 30 seconds off and repeat.

                  heatsink is getting hot during this. I'll take a small video of a few cycles of it and post it
                  Last edited by aarone; 05-04-2017, 09:59 PM.


                  • #10
                    Yeah, this is not a board you really want to mess with. I bet this machine was dropped. Probably a ripped trace/pad somewhere.....


                    • #11
                      donor board it is...

                      It did not die in vain. It gave it's U1950 so that another 820-3437 might live again.
                      First board I've fixed too.
                      Last edited by aarone; 05-04-2017, 10:37 PM.


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