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820-2877-b with fluctuations on ppbus_g3h

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  • 820-2877-b with fluctuations on ppbus_g3h

    Hi I got this board a while back but hadn’t bothered to look at it. I’m just trying to learn these repairs and I’m sorry the majority of the boards are old. Anyway I replaced d7005 one of the diodes was no good it had continuity in diode mode in both direction while the other side did not pin 3had 0 continuity to r7005 so I ran a wire. I u7200 had a short to ground on pin 16. Test pin 16 without u7200 .469v Replaced u7200. No I have a green light on the charger and ppbus_g3h is turning on every 30 seconds almost as if it’s sensing a current draw and shouting down.

    U7000
    chgr_dcin = 16.59v
    chgr_acin = 4v
    smc_bc_acok = 3.3
    pp5v1_chgr_vddp =4.9v
    chgr_rst_l =3.41v

    u7200
    5v3v3s5_reg3=
    3v3s5_entrip=

  • #2
    3V3_S5 tries to appear?
    Post basic voltages for U7200, pins 16, 13, 3, 8, 17.
    Post real voltage on pins 1 & 6 too.

    Comment


    • #3
      Hi yes I just rotated u7200 and now I have good
      ppbus_g3h = 12.56v
      pp5v_s5 = 5v
      pp3v3_s5 =3.3v
      tried power on pads and nothing the pad also has 3.42v
      no s3 or s0 rails

      Comment


      • #4
        C7755 correct voltage present?
        Post resistance to ground (ohm scale) at L6995; should be higher than 30K.

        Check all RTC signals.

        Comment


        • #5
          C7755 pin 1 =.908v
          L6995 =5.98m ohms
          rtc_rst_L =3.42v
          Rtc_clk32k_xtalin = 1.663v

          Comment


          • #6
            Will check other “RTC” signals in a little bit

            Comment


            • #7
              Rtc_clk32k_xtalout_r = 1.743v

              Comment


              • #8
                SM_INTRUDER_L and PM_RSMRST_L good?
                Trigger SMC_ONOFF_L and check for drop pulse at PM_PWRBTN_L.

                Comment


                • #9
                  Sm_intruder_L =3.4v
                  pm_rsmrst_L = 3.4v
                  I’m having a hard time finding a point to check drop pulse at pm_pwrbtn_L one is un smc and the other is under cpu. I don’t see a test point or resistor to test from in between the two points.

                  Comment


                  • #10
                    When I use power on pads
                    smc_onoff_L it doesn’t drop or even move

                    Comment


                    • #11
                      Also c2620 is not present and looks like it’s knocked off.
                      pp3v3r1v8_so_mcp_ifp_vdd on pin 1 pin 2 is gnd

                      Comment


                      • #12
                        "smc_onoff_L it doesn’t drop or even move"
                        Do you mean is always 3V, or just 0V?

                        C2620 shouldn't be a reason for not starting, but I recommend you to solder it anyway.
                        Old platform, no way to measure PM_PWRBTN_L; sorry, didn't check that on schematic.

                        Comment


                        • #13
                          Sorry I meant it stay high at 3.4v

                          Comment


                          • #14
                            These old machines get failing power button.
                            Check first if R5710 is good.

                            Use R5014/15 and check for pulse at PM_SLP_S4_L.
                            Be aware, MCP could be bad, after so many years.
                            You can try heating it...

                            Comment


                            • #15
                              Shorted the point r5014 got no pulse at I’ve got nothing at pm_slp_s4_L =0v

                              Comment

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