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820-2533 Macbook Pro - SYS_ONEWIRE: 0

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    820-2533 Macbook Pro - SYS_ONEWIRE: 0

    15 inch macbook pro charger bulb doesn't come on. Seems there is a problem with SMC. The measured voltages given below. What could be the issue and and how can I go ahead?

    PPBUS_G3H: 12.6
    PP3V42_G3H: 3.4
    SMC_BC_ACOK: 3.2
    PP1V2_S5_SMC_VDD
    SMC_RESERT_L: 3.3
    SYS_ONEWIRE: 0
    SMC_PM_G2_EN: 3.4
    PP5V_S3:0

    #2
    Re: 820-2533 Macbook Pro - SYS_ONEWIRE: 0

    SMC should be ok.
    Try another Magsafe and DC-in board.
    Check voltages on U6900 and U6901.
    OpenBoardView — https://github.com/OpenBoardView/OpenBoardView

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      #3
      Re: 820-2533 Macbook Pro - SYS_ONEWIRE: 0

      SMC_BC_ACOK_VCC is 3.3V

      So U6901 is giving the proper output.
      U6900 getting the 3.3V to VCC pin. R6929 is not open.
      Magsafe is woking fine with another computer
      Last edited by senakahks; 08-21-2020, 11:08 PM.

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        #4
        Re: 820-2533 Macbook Pro - SYS_ONEWIRE: 0

        What about voltage on pins 4 and 5 of U6900?
        And resistance to ground on pin 4 and 5?
        OpenBoardView — https://github.com/OpenBoardView/OpenBoardView

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          #5
          Re: 820-2533 Macbook Pro - SYS_ONEWIRE: 0

          U6900
          Pin4 = 0V
          pin5 = 0V

          Resistance to ground
          Pin4 = 123 Ohms
          Pin5 = 1.7 M Ohms

          Comment


            #6
            Re: 820-2533 Macbook Pro - SYS_ONEWIRE: 0

            Remove U6900 and check voltage and resistance to ground on pin 4 again.
            OpenBoardView — https://github.com/OpenBoardView/OpenBoardView

            Comment


              #7
              Re: 820-2533 Macbook Pro - SYS_ONEWIRE: 0

              Pin 4 pad
              Voltage 3.4V
              resistance to ground 5.4 M Ohms
              Last edited by senakahks; 08-23-2020, 04:26 AM.

              Comment


                #8
                Re: 820-2533 Macbook Pro - SYS_ONEWIRE: 0

                Seems like U6900 was bad, replace with a new one (or from donor board).
                OpenBoardView — https://github.com/OpenBoardView/OpenBoardView

                Comment


                  #9
                  Re: 820-2533 Macbook Pro - SYS_ONEWIRE: 0

                  Great support. Thank you!

                  So, even multimeter is not beeping, a resistance ~ 100 ohms via a chip to ground can be considered as a short to ground. Isn't it?

                  Comment


                    #10
                    Re: 820-2533 Macbook Pro - SYS_ONEWIRE: 0

                    Yes, in fact continuity mode with beep will often be misleading. It really depends on the line you are measuring. On CPU VCore power rail you'd have like 6 ohms and it'd beep but that's normal. On a data line you often expect at least a kiloohm.
                    OpenBoardView — https://github.com/OpenBoardView/OpenBoardView

                    Comment


                      #11
                      Re: 820-2533 Macbook Pro - SYS_ONEWIRE: 0

                      Valuable information. After replacing U6900, now green bulb works on charger. Fan is not working yet. Have to check now.

                      Comment


                        #12
                        Re: 820-2533 Macbook Pro - SYS_ONEWIRE: 0

                        Now SYS_ONEWIRE: 2.8V
                        Green Light is ON
                        S3 rails are not active yet.
                        Last edited by senakahks; 08-24-2020, 04:13 AM.

                        Comment


                          #13
                          Re: 820-2533 Macbook Pro - SYS_ONEWIRE: 0

                          You have to trigger power button for this machine to turn on.
                          OpenBoardView — https://github.com/OpenBoardView/OpenBoardView

                          Comment


                            #14
                            Re: 820-2533 Macbook Pro - SYS_ONEWIRE: 0

                            Tried to trigger by touching the ground to SMC_ONOFF_L. Fan doesn't move at all.

                            Comment


                              #15
                              Re: 820-2533 Macbook Pro - SYS_ONEWIRE: 0

                              Some voltages may be useful:
                              PM_PWRBTN_L: 3.4V
                              SMC_ONOFF_L: 3.4V
                              PM_SLP_S4_L: 0V

                              When trigger SMC_ONOFF_L, PM_PWRBTN_L goes down and come up.
                              Last edited by senakahks; 08-24-2020, 06:47 PM.

                              Comment


                                #16
                                Re: 820-2533 Macbook Pro - SYS_ONEWIRE: 0

                                The charger I have used is a 15V one. So, once charger is changed, SYS_ONEWIRE gives 3.3V
                                Still no luck with FAN
                                Last edited by senakahks; 08-24-2020, 06:54 PM.

                                Comment


                                  #17
                                  Re: 820-2533 Macbook Pro - SYS_ONEWIRE: 0

                                  You must use a good 85W Magsafe.
                                  OpenBoardView — https://github.com/OpenBoardView/OpenBoardView

                                  Comment


                                    #18
                                    Re: 820-2533 Macbook Pro - SYS_ONEWIRE: 0

                                    Yes. That is what I am using now.
                                    What can I check for missing PM_SLP_S4_L?

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