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Hammond A100 with Leslie kit # 7850

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  • Hammond A100 with Leslie kit # 7850

    I'm trying to use my Hammond A100 with the two-channel Leslie kit #7850. Since the A100 has separate amps for main speakers and reverb speaker, this should be possible. I'm following the kit's intallation instructions, which are:

    =======================================
    The brown and orange wires are for channel 1 and the red and yellow for channel 2 of the console connector.
    1. Connect the black wire to the organ "main" speaker ground.
    2. Remove the signal wire from the "main" speaker in the organ; attach it to the RED wire from the console connector.
    3. Attach the YELLOW wire to the speaker terminal just vacated.
    4. Remove the signal wire from the "flute/tibia" speaker in the organ: attach it to the BROWN wire from the console connector.
    5. Attach the ORANGE wire to the speaker terminal just vacated.
    =======================================

    Here's my problem: The A100 has TWO main speakers, not just one. So which of the two main speakers should be wired to the brown and orange connectors in steps 4 and 5? The middle speaker? Or the one on the right? (Reverb speaker is on the left.)

    Thanks for any help you can give.

    Best wishes,
    Jack Lyon

  • #2
    Middle speaker. That's where the amp attaches.

    Geo

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    • #3
      Originally posted by geoelectro View Post
      Middle speaker. That's where the amp attaches.

      Geo
      Thank you! That seems to work, but only IF I skip step #2 in the instructions. Thoughts?

      Comment


      • #4
        I have my doubts whether this kit would work in an A100. Looking at the schematic, when the switch is in the echo position the AO39 sees a 133 ohms (R2 & 4) ro signal gnd.

        Jim

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        • #5
          Originally posted by Jaim View Post
          I have my doubts whether this kit would work in an A100. Looking at the schematic, when the switch is in the echo position the AO39 sees a 133 ohms (R2 & 4) ro signal gnd.

          Jim
          Thanks, Jim, but is 133 ohms too much or too little? Sorry, but I don't know enough. What are R2 and 4?

          Comment


          • #6
            Originally posted by Jaim View Post
            I have my doubts whether this kit would work in an A100. Looking at the schematic, when the switch is in the echo position the AO39 sees a 133 ohms (R2 & 4) ro signal gnd.

            Jim
            Yes, that needs to be adressed - this kit appears to be made for solid-state organs and so the load resistors need to be adapted to work with tube amplifiers. It can be done, sure, but it's a bit of work. Remove resistors R2 and R3, and wire in jumpers in their place. Replace resistors R4 and R5 with 10 ohm / 10 watt resistors.

            Also, the A-100 isn't really a 2-channel organ in the true sense of the term. You need to make sure that you don't break up the connections in the "wrong" place. The reverb amp gets its input signal from the leads to the main speaker; so you need to make sure to move that connection to the "input" of the Leslie kit as well - otherwise you'll only have reverb in the "main" and "ensemble" positions of the switch.

            I _think_ that should cover it, but I may very well be overlooking something. Anyone?

            http://www.fishorgans.com/leslie_kits/007850B.pdf
            Current organs: AV, BC, A-100
            Current Leslies: 22H, 142, 147, 760
            Organs in the past: L-100 (several), M-100 (x2), T-100, E-100, CV
            Other keyboards: Roland FP-4, Yamaha DX7, Yamaha TX81Z, Yamaha Motif ES Rack, Korg Krome, Novation Mininova

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            • #7
              Thanks very much for this information. I really appreciate your help with this.

              I should have mentioned that I'm using a Leslie model 720, which is two-channel. I'd like to send the main signal from the A100 to the rotary channel, and the reverb to the stationary channel.

              I previously bridged the two amps in the 720, effectively making it one-channel. That worked fine, but I really wanted to have the reverb as well, and not through the rotary channel.

              So that's the goal here: Main Hammond signal to 720 rotary channel, reverb signal to 720 stationary channel.

              Thanks again for your help.
              Last edited by EditorJack; 07-16-2017, 12:21 PM.

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              • #8
                The other question is: Do you want the MEE switch to function?

                Jim

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                • #9
                  Yes! Although I don't care about Ensemble. I do want to be able to switch between Hammond and Leslie.

                  Comment


                  • #10
                    The A100 has a balanced output from the AO28 preamp to the AO39 power amp. The reverb amp takes a speaker level output off the AO39 and runs it into the reverb amp compressor, through the spring and back into the amp to the speaker. So anything you do with the main amp will affect the reverb. In addition the main and reverb amps are tube driven which means bad things will happen if you mess with the load on the output transformers.

                    SO - what to do. The balanced input going into the AO39 from the GG terminals of the preamp should be a red/black twisted pair. The brown wire is the signal ground. Try connecting the channel 1 in from the kit to either the red or black wire on the AO39. Connect the kit signal ground (black) to the brown wire on the AO39. The preamp signal is pretty hot so it should work. You won't have MEE but its something. You can mute the A100 main amp by pulling the 5U4 rectifier tube of the AO39.

                    Jim

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