Signal Booster repair

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  • badcapjerboard
    Senior Member
    • Apr 2023
    • 68
    • USA

    #1

    Signal Booster repair

    Can anyone please help me identify the chip needed for replacement?
    Seems the dc jack breaking off the board broke this device. There is a chip with a hole blown through it which I removed, but I can't tell what was written on it or get any useful info with a meter. I'm assuming it's a transistor.
    It looks the same as a chip nearby which says 4R_s 94 but clearly said something different. Can anyone tell me what is an appropriate replacement or how to figure it out?
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    blue arrow removed chip. also knocked out little capacitor below it.
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  • CapLeaker
    Leaking Member
    • Dec 2014
    • 8190
    • Canada

    #2
    I don’t think it is a transistor like a NPN or PNP, more like a Zener diode or something like that. Look at the trace and pin config where the SOT-23 device was, You got the traces for bottom 2 pins together where the SOT-23 on the PCB would be. Wouldn’t make any sense having a transistor there, other than that the other amps would have to have the same transistor and they do not.

    Maybe the SOT-23 marking is Z7 = 8.2V Zener.

    Comment

    • badcapjerboard
      Senior Member
      • Apr 2023
      • 68
      • USA

      #3
      Thank you. Appreciate it! Will try to find one and see what happens..

      Comment

      • CapLeaker
        Leaking Member
        • Dec 2014
        • 8190
        • Canada

        #4
        Anyway, that's all I could come up with… look at the broken SOT23 with you DMM in diode mode and check the pads on the board, not that something else is shorted to gnd as well.

        Comment

        • badcapjerboard
          Senior Member
          • Apr 2023
          • 68
          • USA

          #5
          Ya, the pads are all shorted to ground still. I can't get a reading with a dmm on the blown chip.

          Comment

          • CapLeaker
            Leaking Member
            • Dec 2014
            • 8190
            • Canada

            #6
            check out the mlcc smd cap next o it on the right

            Comment

            • badcapjerboard
              Senior Member
              • Apr 2023
              • 68
              • USA

              #7
              The big cap to the right on my esr meter showed as ref for 25v e cap good if cap <47 uF
              But right above that, second to the right shows as bad cap with high esr. I removed it and it didn't change anything.
              Last edited by badcapjerboard; 01-04-2024, 02:17 PM.

              Comment

              • CapLeaker
                Leaking Member
                • Dec 2014
                • 8190
                • Canada

                #8
                the top and the bottom right pad of the SOT-23 are joined together. The bottom left pin is GND. There has to be a through hole and probably the story continues on the other side of the PCB.

                Comment

                • badcapjerboard
                  Senior Member
                  • Apr 2023
                  • 68
                  • USA

                  #9
                  What a pain. the connectors at both ends were soldered onto the board so that I had to desolder them to get the board out. And the bottom of the board has a metal plate attached so I can't see the traces.

                  Comment

                  • CapLeaker
                    Leaking Member
                    • Dec 2014
                    • 8190
                    • Canada

                    #10
                    yeah... it's shielded all right. That's a pain in the rear to get off, if you don't have the right equipment.

                    Comment

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