JBL Subwoofer SUB200/230 - intermittently goes quiet

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  • synapse
    Senior Member
    • Jun 2012
    • 51
    • Australia
    #1

    JBL Subwoofer SUB200/230 - intermittently goes quiet

    Hi,
    I have been given this Sub to try and fix.
    It seems to go quiet after a while, sometimes turning the sub level dial at the rear makes it loud again. (when it's quiet it just sounds like someone has turned the volume down.

    I thought this variable resistor might be faulty, but after removing it it seems to test fine, a nice gradual rise and fall in resistance on the multimeter.

    Has anyone got ideas of what to check next?
    Attached Files
    I'm currently a Part-time Computer Systems Engineering student.
    Full time Service Assurance (faults) for a large Telco.
    Tags: None
    • synapse
      Senior Member
      • Jun 2012
      • 51
      • Australia
      #2
      Re: JBL Subwoofer SUB200/230 - intermittently goes quiet

      These are top and bottom of the two boards inside
      Attached Files
      I'm currently a Part-time Computer Systems Engineering student.
      Full time Service Assurance (faults) for a large Telco.

        Comment

        • synapse
          Senior Member
          • Jun 2012
          • 51
          • Australia
          #3
          Re: JBL Subwoofer SUB200/230 - intermittently goes quiet

          and this is a little add of board near where i removed the Potentiometer
          Attached Files
          I'm currently a Part-time Computer Systems Engineering student.
          Full time Service Assurance (faults) for a large Telco.

            Comment

            • Khron
              Badcaps Legend
              • Sep 2006
              • 1350
              • Finland
              #4
              Re: JBL Subwoofer SUB200/230 - intermittently goes quiet

              On one hand, i don't suppose you'd be inclined to attempt to trace out at least some of the (input) circuitry, would you?

              And on the other hand, on a Jamo Sub 200 that i bought faulty last year, both the low-pass adjust pot and the volume pot had went wonky, so... Even if the volume pot seems to measure ok, a replacement one can't be more than a buck or two It's not like they used Alps Blue Velvet ones as stock, anyway
              Khron's Cave - Electronics - Audio - Teardowns - Mods - Repairs - Projects - Music - Rants - Shenanigans

                Comment

                • Agent24
                  I see dead caps
                  • Oct 2007
                  • 4958
                  • New Zealand
                  #5
                  Re: JBL Subwoofer SUB200/230 - intermittently goes quiet

                  Could have been bad solder joints on the potentiometer - the movement caused by turning it may have restored connection momentarily.

                  Replace the potentiometer and if it still shows the fault, you could trace the signal with another amp or scope and see if you can find out what happens to it when it level drops.
                  "Tantalum for the brave, Solid Aluminium for the wise, Wet Electrolytic for the adventurous"
                  -David VanHorn

                    Comment

                    • budm
                      Badcaps Legend
                      • Feb 2010
                      • 40746
                      • USA
                      #6
                      Re: JBL Subwoofer SUB200/230 - intermittently goes quiet

                      This may help.
                      Attached Files
                      Never stop learning
                      Basic LCD TV and Monitor troubleshooting guides.
                      http://www.badcaps.net/forum/showthr...956#post305956

                      Voltage Regulator (LDO) testing:
                      http://www.badcaps.net/forum/showthr...999#post300999

                      Inverter testing using old CFL:
                      http://www.badcaps.net/forum/showthr...er+testing+cfl

                      Tear down pictures : Hit the ">" Show Albums and stories" on the left side
                      http://s807.photobucket.com/user/budm/library/

                      TV Factory reset codes listing:
                      http://www.badcaps.net/forum/showthread.php?t=24809

                        Comment

                        • synapse
                          Senior Member
                          • Jun 2012
                          • 51
                          • Australia
                          #7
                          Re: JBL Subwoofer SUB200/230 - intermittently goes quiet

                          Thanks guys, If i get a chance over the next few days I'll re solder in a new one then see what happens.
                          That service manual is gold, thankyou very much.
                          I'm currently a Part-time Computer Systems Engineering student.
                          Full time Service Assurance (faults) for a large Telco.

                            Comment

                            • synapse
                              Senior Member
                              • Jun 2012
                              • 51
                              • Australia
                              #8
                              Re: JBL Subwoofer SUB200/230 - intermittently goes quiet

                              Just an update: Replaced the potentiometer and it's working like new now.

                              Thanks for your help.
                              I'm currently a Part-time Computer Systems Engineering student.
                              Full time Service Assurance (faults) for a large Telco.

                                Comment

                                • budm
                                  Badcaps Legend
                                  • Feb 2010
                                  • 40746
                                  • USA
                                  #9
                                  Re: JBL Subwoofer SUB200/230 - intermittently goes quiet

                                  Thanks for the follow-up.
                                  Never stop learning
                                  Basic LCD TV and Monitor troubleshooting guides.
                                  http://www.badcaps.net/forum/showthr...956#post305956

                                  Voltage Regulator (LDO) testing:
                                  http://www.badcaps.net/forum/showthr...999#post300999

                                  Inverter testing using old CFL:
                                  http://www.badcaps.net/forum/showthr...er+testing+cfl

                                  Tear down pictures : Hit the ">" Show Albums and stories" on the left side
                                  http://s807.photobucket.com/user/budm/library/

                                  TV Factory reset codes listing:
                                  http://www.badcaps.net/forum/showthread.php?t=24809

                                    Comment

                                    • Agent24
                                      I see dead caps
                                      • Oct 2007
                                      • 4958
                                      • New Zealand
                                      #10
                                      Re: JBL Subwoofer SUB200/230 - intermittently goes quiet

                                      Awesome! Good to hear.
                                      "Tantalum for the brave, Solid Aluminium for the wise, Wet Electrolytic for the adventurous"
                                      -David VanHorn

                                        Comment

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