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820-2936 green light no fan spin

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  • 820-2936 green light no fan spin


    This board was liquid damaged, repaired and working. Somehow a screw dropped on it sometime after, no idea how they pulled that off. Anyhow, I was missing PP5V_SUS and Q7840 was replaced, PP5V_SUS came back.

    Sometimes the fan tries to move bit stops, it's not even a quarter spin, it's like a blip. I have PPVCCSA_S0_REG but I do not have PPVCORE_S0_CPU_PH2 or PH1

    If I leave it on long enough, the CPU does get a little warm but, not hot, also when I plug in a mouse, it does light up but a USB drive stick does not.

    Any idea what to look for next?

  • #2
    VCORE always stays at 0V?
    Nor even a pulse when charger is connected, or triggering SMC_ONOFF_L?
    Other coils should get voltage before VCORE appears; check for pulse on them at least.
    Check for pulse at PM_SLP_S4_L and 5V_S3 coil first; especially if no fan movement detected.
    Also try to start in SMC bypass mode...


    • #3
      No pulsing all, when charger connected or triggering SMC_ONOFF_L, SMC Bypass, the fan does come on but no boot or chime.

      Is it something with the bios/traces or clock signal?


      • #4
        "No pulsing all"
        Nor even PM_SLP_S4_L?
        Do you get 3V3_S5 and 3V3_SUS?

        "SMC Bypass, the fan does come on but no boot or chime"
        Board stays on then?


        • #5
          no pulsing PM_SLP_S4_L it's a steady 3.3v, SMC bypass board stays on "fan stays going" I do get 3V3_S5 and 3V3_SUS 3.3v each.


          • #6
            In SMC bypass, do you get voltage on all coils, less the CPU ones?

            I was interested for 3V3_S5/SUS in normal mode, when the board doesn't start...
            Check if AVREF_SMC voltage is present.


            • #7
              3V3_S5/SUS without bypass is 3.3v and SMC bypass is 3.3v as well.
              AVREF_SMC is 3.3v with and without SMC bypass

              I get voltage on all coils except the PPVCORE_S0_CPU_PH2 or PH1 and PPVCORE_S0_AXG_R in normal and in SMC bypass

              Also noticed ppbus_g3h is 12.6v normal but in bypass it's 12.33v, I assume that is due to me bypassing it? If not, then I guess SMC issues?


              • #8
                That is normal for SMC bypass.

                So the board stays on even in normal mode?
                Check R7402.


                • #9
                  The board stays on in normal mode, minus the vcore of course.
                  r7402, 7mv on pin 1 and 12.60v on pin 2. Even in SMC bypass, it measures the same
                  Also, resistance is 55k, which should be 90.9k, so I removed the resistor out of the circuit and it measures 90k to be sure it's good.


                  • #10
                    Post some voltages for U7400; pins 1, 15, 24, 40.
                    You may need to change it...


                    • #11
                      pin 1 = 28.9mv
                      pin 15 = 5v
                      pin 24 = 5v
                      pin 40 = 5v


                      • #12
                        you don't get a pulse at pin1, at least?
                        ALL_SYS_PWRGD is high?
                        Do you get 25MHz at pin 9/U2800?

                        If you get 0V at pin 2/U7400 without enable present, I recommend you to change U7400.

                        Check all SPI Bus Series Termination resistors and check for corrosion around U6100.
                        You can also try reflashing BIOS.


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