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A1990 820-01326-05 stuck on 20v

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    A1990 820-01326-05 stuck on 20v

    thank you for allowing me to participate in this Forum, as a hobby I delight in the repair of macbooks, I am a beginner, I have this macbook that I bought to try to get it back in operation.
    At the first attempt it turned on it seemed to have a correct absorption of amps and seemed to charge the battery, from the beginning there seemed to be activity as the trackpad seemed to respond to impulses. Obviously it never turned on, no sound, the fans never turned. It does not heat in any point, observed with a thermal imager. A newbie question, does this type of macbook start up with no battery connected?
    I tried before and to perform other operations a DFU restore but it was not successful returning errors almost at the end of the process.
    The logic shows no signs of the presence of oxides or liquids.
    It has a strange behavior, without battery connected it remains stable at 20v but with variable absorption from 0.03A-0.07A if I connect the battery v from 20v to 5v, cyclically.
    Here are the measurements I made:

    PPBUS_G3H - 12,60v
    PPBUS_HS_CPU - 12,60v
    PPBUS_HS_OTH5V - 12,60
    PP5V_G3S - 5v
    PP3V3_G3H_T - 3,3
    PP2V5_NAND_SSD0 = 2,5v
    PP1V8_SSD0 = 1,8v
    0V9_SSD present and stable

    U7701
    Pin 12 5,1v
    Pin 6 2,8v to 3,1v oscillating and unstable
    Pin 16 0v
    Pin 17 0v


    L8102 0.06
    L7030 0.43
    L7701 0.08
    L8410 0.78
    LB700 0.26
    L7660 0.40

    Also it has a strange behavior, a continuous variation of the voltage on r3460 and r3450, from 0.5v to 1.8v with continuous oscillation, I replaced u3200 and it is now stable on 0.8v

    I repeat, I am a beginner, forgive me if I make any mistakes in the description :giggle:

    #2
    Re: A1990 820-01326-05 stuck on 20v

    Can you post the schematic and boardview files for the 820-01326-05 ? Do not see these in my database.

    Remove all power -> meter in resistance mode.

    Check the resistance to ground of U7701, pin 6 that is oscillating.

    More after reviewing the schematics.

    Comment


      #3
      Re: A1990 820-01326-05 stuck on 20v

      unfortunately I have not found that schematic anywhere and am trying to compare with 820-01041.
      As soon as I get home in the afternoon I will carry out the test you suggested on U7701 pin 6
      Tks ;-)

      Comment


        #4
        Re: A1990 820-01326-05 stuck on 20v

        now the situation has changed, without changing other components:
        PPBUS_G3H - 12.60v
        PPBUS_HS_CPU - 12.60v
        PPBUS_HS_OTH5V - 12.60
        PP5V_G3S - 5v
        PP3V3_G3H_T - 3.3
        PP2V5_NAND_SSD0 = 2,5v
        PP1V8_SSD0 = 1,8v
        U7701
        Pin 12 - 5,1v
        Pin 6 - 0V
        Pin 16 - 0v
        Pin 17 - 0,20v
        u7701
        resistance to mass
        PIN 6 - 50 kΩ
        pin 17 - 83 kΩ
        pin 16- slowly increases > 180Ω>>>>>>>

        Comment


          #5
          Re: A1990 820-01326-05 stuck on 20v

          what will it be that triggers this instability? unfortunately my skills are not that advanced .... I'm stalled

          Comment


            #6
            Re: A1990 820-01326-05 stuck on 20v

            For now, do not use the battery.

            Reaching 20v with adapter is a good sign to validate that each of the ACE controllers is working to allow for this power delivery contract.

            Meter in diode mode.

            Remove all power to the logic board.

            Red meter probe to ground (yes red probe).

            Black meter probe to point to test.

            Check diode mode to ground on all power rails of SSD.

            Post the values.

            Comment


              #7
              Re: A1990 820-01326-05 stuck on 20v

              here are the measures, after, i also read the tensions, i hope it is right

              PP3V3_G3H_SSD0_SNS = 0,40
              PP3V3_G3H_SSD1_SNS = 0,40
              PPBUS_G3H_SSD0_SNS = 0,37
              PPBUS_G3H_SSD1_SNS = 0,37

              PP3V3_G3H_SSD0_SNS = 3,3v
              PP3V3_G3H_SSD1_SNS = 3,3v
              PPBUS_G3H_SSD0_SNS = 12,60v
              PPBUS_G3H_SSD1_SNS = 12,60v

              Comment


                #8
                Re: A1990 820-01326-05 stuck on 20v

                I'm not very experienced but they would seem normal values, am I doing something wrong?

                Comment


                  #9
                  Re: A1990 820-01326-05 stuck on 20v

                  Remove all power. Meter in diode mode.

                  Red meter probe (yes red probe) to ground.

                  Black meter probe to test point:

                  PP1V8_SLPS2R

                  What is the reading ?

                  Comment


                    #10
                    Re: A1990 820-01326-05 stuck on 20v

                    thank you very much for the help you are giving me ;-), you are very kind
                    here is the measurement:

                    PP1V8_SLPS2R 0,37

                    Comment


                      #11
                      Re: A1990 820-01326-05 stuck on 20v

                      can i do other tests? :testa di botto:

                      Comment


                        #12
                        Re: A1990 820-01326-05 stuck on 20v

                        Originally posted by sdogs View Post
                        thank you very much for the help you are giving me ;-), you are very kind
                        here is the measurement:

                        PP1V8_SLPS2R 0,37
                        can i do other tests? :pensiero:

                        Comment

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