JBL CSMA1120 amplifier

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  • Bterrier
    Senior Member
    • Apr 2018
    • 72
    • USA

    #1

    JBL CSMA1120 amplifier

    I recently picked up a jbl csma1120. Seems to work well, however the bass and trebles knobs are missing. I wouldn't mind if there were still a way to adjust the bass and treble, but there is nothing to turn, just printed circuit board behind the holes.

    Is this repairable? How to these knobs work and install. I was expecting to see a shaft of a potentiometer where the knobs are missing.
  • petehall347
    Badcaps Legend
    • Jan 2015
    • 4426
    • United Kingdom

    #2
    Re: JBL CSMA1120 amplifier

    pictures please .
    is there a remote ?

    Comment

    • Bterrier
      Senior Member
      • Apr 2018
      • 72
      • USA

      #3
      Re: JBL CSMA1120 amplifier

      No remote. It is more of a commercial amp. It can run 4 or 8 ohm loads as well as 70v and 100v systems.

      I will upload a few pics later tonight.


      https://jblcommercialproducts.com/en.../csma-180-1120

      Comment

      • R_J
        Badcaps Legend
        • Jun 2012
        • 9535
        • Canada

        #4
        Re: JBL CSMA1120 amplifier

        Looks like they are/were screwdriver adjustments, no knobs, so they are either pushed in or broken

        Comment

        • Bterrier
          Senior Member
          • Apr 2018
          • 72
          • USA

          #5
          Re: JBL CSMA1120 amplifier

          Yes, the plastic piece/knob that you would turn with a screwdriver is missing. Im tryng to find a solution. If I can get those pieces from JBL, how would they be installed. Im confused how they work

          Comment

          • Bterrier
            Senior Member
            • Apr 2018
            • 72
            • USA

            #6
            Re: JBL CSMA1120 amplifier

            Photo attached. Printed circuit board within the holes. It actually looks like the head of a screw, and the lighting wasnt so good in my work area, I actually tried to use a screwdriver to turn it.

            There are also 2 pads/contacts above the screw print, I'll try to get a better photo when I can






            Attached Files

            Comment

            • R_J
              Badcaps Legend
              • Jun 2012
              • 9535
              • Canada

              #7
              Re: JBL CSMA1120 amplifier

              It looks like the controls are still intact and could be adjusted with a small screwdriver if needed, getting those little extentions from jbl???, good luck
              if not this pdf might help
              Attached Files
              Last edited by R_J; 06-20-2018, 08:49 PM.

              Comment

              • Bterrier
                Senior Member
                • Apr 2018
                • 72
                • USA

                #8
                Re: JBL CSMA1120 amplifier

                No, it can't be adjusted with a screwdriver. This is my issue.

                I know it looks like a Philip's screwdriver would work, but that is only an image of a Philip's screw head which is printed on the circuit board. There are no moving parts.

                Attached Files

                Comment

                • R_J
                  Badcaps Legend
                  • Jun 2012
                  • 9535
                  • Canada

                  #9
                  Re: JBL CSMA1120 amplifier

                  Those are APC brand pots (apc spain), just like in the picture I provided (3rd pot), the blue is the pot, the white with the cross is the part that turns, and the black is what is left of the broken knob. You don't use a philips, you use a small flat blade, like a jewelers screwdriver.

                  Whats left of the black knob might be able to be pushed out, It depends on how the pot is mounted.
                  The pdf I provided has shafts that should work if you can not get the originals from JBL
                  If it is a CA6 size pot Page 4 number 6031 looks similar, If its a CA9 page 12 has the shafts
                  Attached Files
                  Last edited by R_J; 06-21-2018, 06:43 AM.

                  Comment

                  • Bterrier
                    Senior Member
                    • Apr 2018
                    • 72
                    • USA

                    #10
                    Re: JBL CSMA1120 amplifier

                    Thanks for the info. After further inspection, it appears you are correct. It seems as the plastic extension is broken off flush with the pot. How would I go about attempting to remove the broken piece?

                    If I am unsuccessful, I will replace the pots but I am trying to avoid that if possible because everything seems to be functional.

                    Comment

                    • R_J
                      Badcaps Legend
                      • Jun 2012
                      • 9535
                      • Canada

                      #11
                      Re: JBL CSMA1120 amplifier

                      Just use a small screwdriver that fits the slot, that black plastic should just push out the back of the pot. It should take very little force so no hammer
                      Last edited by R_J; 06-21-2018, 08:41 AM.

                      Comment

                      • Bterrier
                        Senior Member
                        • Apr 2018
                        • 72
                        • USA

                        #12
                        Re: JBL CSMA1120 amplifier

                        Thanks I didnt realize the back was open. All set now, just need the extensions.

                        Comment

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