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  • Hammond Tone Cabinet (JR-20) fuzz



    Hi there,</p>

     Can anyone here tell me what could be causing this static? </p>

    <span class="Apple-style-span" style="white-space: pre-wrap; ">http://hermes.zshare.net/stream/f6fc6ea6b7c19b8731801f8bc9f25852/1224058064/20572504/1224025549.wav</span> </p>

     I have tried wiggling all the tubes in the JR-20 amp, and no more or less noise is heard.  I will try to find a culprit tube on my C-2 amp tomorrow, but I'm just curious if this is a common thing.  Also, is there a chance that this could be a capacitor issue?</p>

     I know that most JR-20s were made with some kind of crystal contact/ pickup in the reverb unit, and its probably long gone; so the reverb does not work.  I'm OK with that because the Chapel's acoustics are awesome, but on that note, does anyone have a link to an online service manual for the JR-20?  I'm having a hard time finding a PDF version of that one. </p>

  • #2
    Re: Hammond Tone Cabinet (JR-20) fuzz



    Tough one here. I heard what sounded like ocean surf with a couple of clicks. If I had to guess I would say filter caps in the JR20. Could even be preamp tube(s) in the tone cab. Can you fire up the JR20 on a jumper (disconnected from the organ) and short the signal inputs? If it still makes noise the problem is definately the JR20. If it is silent is the preamp in the C2. Is the reverb level switched to off? Will it play and make organ music? Do you have another tone cab that is known good to test the C2?</P>


    If you're not electrically inclined, I would not recomend this. A mistake here could cause serious injury to you or the equipment.</P>


    H101</P>

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    • #3
      Re: Hammond Tone Cabinet (JR-20) fuzz



      I'm not sure about using a jumper wire with the isolated cabinet, because I'm not sure about the line in voltage/ polarity and such.  (I still can't find the service manual on line.)  The whole setup belongs to a local chapel with absolutely no funding, so I'm doing what I can on my own to help restore the organ.  That being said there are no other tone cabinets/ organs in the area besides my L-100 that is also having some difficulty... It will play, but it seems that as soon as the tubes warm up, I get a distorted sound and the fuzz that you heard in the video.  </p>

       </p>

      The click at the beginning was me turning on the run switch, and the fading in and out was my use of the swell pedal.  </p>

       </p>

      Also, because this setup is new to me, I'm not exactly sure how to work the reverb unit in the tone cabinet.  Any ideas?</p>

       </p>

      RM </p>

      Comment


      • #4
        Re: Hammond Tone Cabinet (JR-20) fuzz



        Since warming of the tubes seems to cause the trouble it very well be power tube (s). You can find your schematic at www.captain-foldback.com .</P>


        Click on Hammond at the bottom of the page then Hammond schematics. Scroll down to the bottom of the page and he has several versions posted.</P>


        There should be a selector switch for the reverb on the back of the chassis. I had a JR20 many years ago. I think there is an off position.</P>


        H101</P>

        Comment

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