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PS48 Bose sub & head unit schematic / advice please.

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    PS48 Bose sub & head unit schematic / advice please.

    PS48 is model for sub & where i suspect issue lies .

    CD head unit seems to run ok , & can take a line out signal into an amp with audio present .

    Can't seem to measure any voltages at secondary side of PSU within SUB unit .
    Attached Files

    #2
    Re: PS48 Bose sub & head unit schematic / advice please.

    Yep ,primary side requires a rebuild .

    First on the list Q101 & Q102 ( ST Electronics P9NB50FP ) . Both S/C , which doesn't surprise me considering the amount of glue across their respective pins that had turned a dark brown colour & no doubt become conductive .
    Attached Files

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      #3
      Re: PS48 Bose sub & head unit schematic / advice please.

      Also replace the following .

      U101 , ST Electronics L6598D

      R101 , 10R

      R103 , 10R
      Attached Files

      Comment


        #4
        Re: PS48 Bose sub & head unit schematic / advice please.

        C119 ( 470NF ) has a leaky resistance reading of 10K
        Attached Files

        Comment


          #5
          Re: PS48 Bose sub & head unit schematic / advice please.

          D150 , marked KJJN9 , which is in fact BAV70 .

          Contains two diodes with a common cathode .

          One of them measuring leaky & become a 2 way street .
          Attached Files

          Comment


            #6
            Re: PS48 Bose sub & head unit schematic / advice please.

            Q104 , marked K3NN7 , which is an MMBT3906 has a low reading of 45R at collector / emitter junction .
            Attached Files

            Comment


              #7
              Re: PS48 Bose sub & head unit schematic / advice please.

              Q103 , marked K72 L7 , O/C .

              Only mentioned on parts list & schematic as being an N-CH-FET .

              Spotted a thread on another forum stating that it's type 2N7002
              Attached Files

              Comment


                #8
                Re: PS48 Bose sub & head unit schematic / advice please.

                Also stated on thread found that the opto's can go leaky .

                Not taking any chances therefore replaced U102 & U103 , both type CNY17F-1
                Attached Files

                Comment


                  #9
                  Re: PS48 Bose sub & head unit schematic / advice please.

                  WOW ,what a mission .

                  All working & on test .

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