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820-3208 - no fan spin

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  • 820-3208 - no fan spin


    i have an 820-3208 in an S0 state. but no fan spin.

    The missing S0 rails are

    incidentally PP1V5_S3_CPU_VCCD is at 1.35v and not 1.5v

    all_sys_pwrgd is not present (50mv)

    I have changed Q7950 twice just in case

    inputs on Q7950 are

    VMON_Q2_BASE 1.06v
    VMON_Q3_BASE 1.3v
    VMON_Q4_BASE 0.7v
    S0PGD 0.65v

    the voltages coming in to each of the resistors (and dividers) feeding Q7950 are fine. the resistors themselves are fine. and the all_sys_pwrgd resistors also seem fine

    any thoughts on where to go next with this board?



  • #2
    If you have doubts with Q7950, remove it.
    The board should work without it.
    If ALL_SYS_PWRGD stays low, VCORE will not appear.
    So check wich power supply involved in generating ALL_SYS_PWRGD fails.
    Check first if R7967 gets 3V at pin1.
    Next, remove one by one R7901 and R7963-66.
    When ALL_SYS_PWRGD goes high, you just found the culprit...


    • #3
      thank you

      removing R7901, R7903-6 sends pwrgd high. measuring on the incoming side of each removed resistor pad gives the following:

      p5vs3_pgood 0.5v
      p3v3s5_pgood 0.5v
      pvccsa_pgood 0v
      cpuvccios0_pggod 0.6v
      p1v8s0_pggod 0.6v

      so i guess a problem on one of the 0v lines.... any known issues to look for on those?


      • #4

        You must check ALL_SYS_PWRGD after each resistor removed.
        You cannot get 3V on the other side of the resistors, as the pull-up R7967 remains on ALL_SYS_PWRGD side...


        • #5
          for example leave R7967 in place; remove the other resistors 7963-8 and test for voltage on pad 1.

          unfortunately now a retrograde step in any event. i had identified that CPUVCCIOS0_EN was not present. went to make a cup of tea and have come back to find that the board is no longer in an s0 state. so I have lost most of the rails. I still have the hot rails but PPVRTC_G3H is only 2.7v.

          no orange light on the charger.



          • #6
            Check now PPBUS_G3H and 3V42 rails...


            • #7
              i have all the always on rails.just RTC is at 2.7v rather than 3v. i will replace the clock chip\


              • #8
                Good luck, I hope PCH is still OK...


                • #9
                  that would be annoying. but I can't see why the PCH would spontaneously have fried.

                  I have swapped the clock chip. Output on RTC is still 2.7v . Also pp3v3_s5 is at 2.7v as is the P3V3S5_DRVH line coming from U7201

                  no enable on U7941. dead SMC?


                  • #10
                    "I can't see why the PCH would spontaneously have fried
                    i had identified that CPUVCCIOS0_EN was not present"
                    You already have something PCH related...

                    Check resistance to ground on VCCRTC and 3V3_S5 lines; be aware, both go to PCH.
                    Compare with a good board, if possible.
                    Also check again all RTC signals.


                    • #11
                      I don't think it can be PCH as that enable signal is generated from pm_slp_s3_r which is also required for other enable lines that I know are functional.

                      i guess either r or c7981 must have been damaged.

                      But of course now the problem is rather wider with no full S5 rails and only 2.7v on pp3v3. I will check the resistances tomorrow morning before work.


                      • #12
                        I don't want to dissapoint you, but PM_SLP_S3_L is controlled by PCH; it also has the pull-up resistor inside.
                        All the sleep signals are controlled by PCH.


                        • #13
                          Sure. But if the signal wasn't being generated then all the other rails that rely on it would not be present. And previously the board was in an S0 state meaning that pm_slp_s3_l was not in an active low state .


                          • #14
                            You're right, it "WAS"...
                            So you can't discard PCH now.
                            C1802/03 are prone to fail on this board.
                            But them cannot drop so much VRTC rail.

                            If U2700 receives correct 3V42, and all caps from VRTC are good (disconnect them for test), then no other reason than bad PCH remains...
                            Last edited by 2informaticos; 12-02-2018, 09:41 AM.


                            • #15
                              resistances on the requested lines are
                              PPVRTC- 4MOhm
                              PP3v3_S5 - 3.8kOhm

                              the always-on rails are present (save that PPVRTC is at 2.7v)

                              SMC_RESET_L,SMS_PWRBTN_L are both high.
                              SMC_PM_G2_EN is at at a few mV.

                              dead SMC?


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