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Speaker on/off switch for M-111

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  • Speaker on/off switch for M-111

    Hi all - I'm new to the forum, and to Hammond ownership - picked up an M-111 in decent shape a couple of weeks ago free on Craig's list (reverb doesn't work though - the tubes in the amp light up but it doesn't turn on). It seems to work fine - not a whole lot of volume (probably needs new tubes), so I hooked it up to an external amp via the phono input on the expression pedal tower (even though folks tell me that's not supposed to work that way, for whatever reason, it works remarkably well), and I'm using a Line 6 Roto Machine for a Leslie sim that sounds pretty good (I know, I know, there's no substitute for a real Leslie, but don't have $ for that right now!). At any rate, what I want to do now is rig a switch to turn the main speakers off and on. I've heard things about 8 ohm load issues for the power amp and I sure don't want to blow up the A0-29! The good folks over at the Harmony Central keyboard forum referred me to youfor some info. Any info you can give would be helpful. Thanks - Chasmac

  • #2
    Re: Speaker on/off switch for M-111



    Yes, the phono jack on the expression box is in fact an input. It will work as an output but it's not the best place to tap an output. This point is right on the grid of the output driver tube and is a rather high impedence.</p>

    You should always keep the amp connected to a load to prevent output transformer damage. Simply switching between the speakers and an 8 ohm resistor will do the trick. At least a 10 watt resistor although I would recommend a 20 to 25 watt.</p>

    Low volume may be a sign of trouble in the amp that should be looked at. It's common for the output bias voltage to fail. This could damage output tubes. I would recommend getting a schematic and either you or a knowledgeable person going through it.</p>

    George
    </p>

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    • #3
      Re: Speaker on/off switch for M-111

      Thanks, George, for the good info. I still don't know which wire to tap into to install the switch and resistor that would shut off all of the speakers at the same time. Has anyone on the forum done this or can refer me to an article on the subject? Where would I get a schematic for this organ? With regard to the low volume, I'm hard of hearing and I don't know how loud this organ should be, so it's probably fine. I know when I put in my hearing aids I can hear it just fine. It's certainly loud enough to be heard across a room, though not loud enough to be heard overthe rest of the instruments in theband (it probably wasn't designed to be that loud!), so that's when I need to run it through an external amp. Thanks again - Chasmac

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      • #4
        Re: Speaker on/off switch for M-111

        simply remove the 6V6 tubes to quiet the organ while using line output.

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        • #5
          Re: Speaker on/off switch for M-111



          [quote user="JonC3"]simply remove the 6V6 tubes to quiet the organ while using line output.
          [/quote]</p>

          Although that certainly quiets the organ, it also raises the DC voltages in the amp because of the loss of the load the power supply was designed for.</p>

          Sounds like he just wants it louder, I would just let it and the external amp play just to keep it simple.</p>

          George
          </p>

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          • #6
            Re: Speaker on/off switch for M-111



            Yes, but not as much to destroy the tubes - around 10V which is the safe +/- 10%. Once I serviced (oiled) an M3 which was working without one 6V6 tube for 10 years.</p>

            But it is always better to install dummy load. I'm only giving the fastest and easiest way...</p>

            Jon</p>

            </p>

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            • #7
              Re: Speaker on/off switch for M-111



              Chasmac,</P>


              You'll find a link to the M-100 service manual (actully the whole m series) in this post: </P>


              http://organforum.com/forums/3/60979...ead.aspx#60979</P>


              (Thanks, xDave &amp; others)</P>


              I'll take a stab at theresistor / switch... You'll findBlack and Green wires attached to the M111 main speakers. Look for the amp side - that is, the bit of Green and Black wires running from the amp to the first speaker. Place the resistor bewteen the Black &amp; Green wires. A few inches more toward the speaker, install your switch on the Green wire. </P>

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              • #8
                Re: Speaker on/off switch for M-111

                Thanks for the how-to, Bones - I'll give it a try! Chasmac

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                • #9
                  Re: Speaker on/off switch for M-111



                  This'll go back to your earlier issues: low volume and no reverb. It's possible there could be an easy fix on both,especially the reverb issue.</P>


                  The connectionsfor the reverbare RCA plugs/jacks. These can become badly oxidized over time (read: 40+ years!), even to the point where no signal can get through at all. So first thing to try is, get some spray contact cleaner, unplug the RCA leads to and from the reverb amp and tank, then spray both plugs and jacks, and re-seat (I like to give them a little twist when I reseat them.) In fact this is a good idea to do on every RCA connector you find in the organ. Also you'll want to spray and reseat any Molex connectors you find -- these are the white plastic, squarish or rectangular plugs. IIRC at least one of the connections to the main power amp utilizes these Molex connectors, so that could potentially be contributing to your volume issue.</P>


                  When I got my L111 it ran but had absolutely no sound. When I got back there and started poking around I found all these oxidized connectors -- some so badly that it took a mighty heave to unplug them! But after I sprayed and plugged everything back in, bingo - full volume, no problem. So this is definitely a first step to take on all these L100/M100 models, especially if they've been sitting unplayed for many years. I'd definitely try this before rushing out to buy a whole new set of tube$! anyway good luck -Scott</P>
                  Nobody loves me but my mother,
                  And she could be jivin' too...

                  --BB King

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