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Fishman Loudbox Acoustic

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  • Fishman Loudbox Acoustic

    I got in a Fishman Artist for repair.
    Ch #1: no output
    CH #2: full output

    Ch #1 was a bad opamp: easy peasy.
    Ch #2 was a whole nother can of worms.

    This amp is an absolute nightmare to work on.
    All of the boards have to come out along with the IEC board.
    Not tech friendly at all.
    (and don't even ask about the crumbly Tolex)

    So I got Ch #2 out of the painted steel chassis and it works fine.
    I did take notice that the ground buss on that board is NOT connected to the control pot shells (as Ch #1 IS).
    Put the board back in, tighten up the control hardware & boom. Full output.
    So I remove the board and I ran a 'ground' wire to different pots and the Mid pot causes the issue when 'grounded'.
    I took the control apart and found one of the wiper contacts bent in such a way that it actually touched the shell of the control.
    Bent it back, reassembled the control and the issue was gone.
    So, as near as I can figure, the control (which did have a loose mounting nut) 'broke' through the paint in the chassis hole and found 'ground'.
    Which begs the question: why was the 'ground' buss not connected on Ch #2?
    (I could not find any cut traces, although being a surface mount PCB, it was hard to tell).
    Did Fishman receive a defective part & this was how they dealt with it?
    Was it a One Off?

  • #2
    My artist is acting up: making crackling noise in the tweeter only: woofer is noise free. It's not the tweeter, as I swapped the woofer for the tweeter, and the problem then occurs with woofer, which exhibits large excursions of the cone.
    Thinking it may be the amp chip: TAS5630B, which is only about $20, but a 64 pin htqfp would be a bear to replace.
    Any chance a schematic is available?


    • #3
      I have not come across the correct schematic.
      But from what I can tell the power amp it is similar to the Loudbox 100.
      LM3886 is the tweeter IC.
      Attached Files


      • #4
        Originally posted by Jazz P Bass View Post
        I have not come across the correct schematic.
        But from what I can tell the power amp it is similar to the Loudbox 100.
        LM3886 is the tweeter IC.
        Jazz, I gotta hand it to you on that one. I've only dealt with two of these in my career, the first one I was able to sort out, thought it was so long ago, I don't recall what it was. The second one was a disaster, and within an hour, seeing how far I'd have to go with it, it wasn't economically viable to continue, and closed it back up. It was one of CenterStaging's inventory units, so it had to be sent out either to Fishman, or some other shop who no doubt charged a bunch of $$ for the repairs. Life is too short to work on those, IMHO.
        Logic is an organized way of going wrong with confidence


        • #5
          Lucky Me!
          I have one coming in next week.


          • #6
            Here's pics of the amp chip used in my artist, see attached links:



            The datasheet for the amp chip is here:

            Since this is bi-amped, and since it appears one channel is used for the woofer and a second channel for the tweeter, I'm just thinking of just adding a 2 way crossover on the working channel (woofer), and calling it a day:


            • #7
              When I needed a schematic for a fishman product I simply called them and they sent it over by email right away. Not saying this is the case with every model and it could be the case where they only send one for older models. Still it is worth a call to find out.

              edit: "Here they are. If you'd like factory service (flat $50 charge plus shipping) at any point, please let me know." This is exactly what was in the email with the schematic sent.
              When the going gets weird... The weird turn pro!


              • #8
                I would check the input pins for the tweeter (C & D?) to see that there is nothing going on there.
                The amp may be 'doing what it's told'.

                Attached Files


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