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AO 28 wiring How to tell which one of the two shielded green yellow go where.

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  • AO 28 wiring How to tell which one of the two shielded green yellow go where.

    Hello i had to rewire a AO 28 preamp on a A100 and i could use some help. I can't figure out which of the 2 shielded green yellow cable go where and i'm missing the brown cable that goes to the left of the green yellow next to the GG. I hooked them at random and the preamp was working but soft and loud where reversed.

  • #2
    Google "Hammond service manual" ... it's out there for free download, and has all the info you need.
    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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    • #3
      Maybe this will help...

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      • #4
        You really need the A-100 wiring diagram, which is in the main Hammond console organ service manual. I tried to upload just the A-100 wiring diagram three times, but the site doesn't like something about the image format and gave me error messages.

        Still, enor is right that all this information is out there for download on the web. It's readily available.


        I'm David. 'Dave' is someone else's name.

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        • #5
          Thank you guys, i did purchase the hard copy of the Hammond service manual and i have the A-100 wiring diagram so i know theoratically where those wires go. But from a practical stand point the wires are all bundled and unmarked so the 2 shielded yellow green look identical . I was curious to see if there was a shortcut to identify them. I guess i'll separate them and trace them.

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          • #6
            The yellow and green wires to the Volume Soft rocker switch do not have grounding tabs on the shields. The yellow/green wires to the preamp inputs do have grounding tabs that screw to the shield around the inputs.

            Was there no preamp in the organ? If there was, it's a good idea to take pictures before you begin disassembly.
            I'm David. 'Dave' is someone else's name.

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            • #7
              Ah thanks David, the organ i got was striped and all cables cut so no ground tabs. But now thanks to you i realize that some of my troubles could be due to a missing ground tab. I guess if i lift the volume switch i can do a continuity test to find the other end without undoing the wire bundle

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              • #8
                [QUOTE= i realize that some of my troubles could be due to a missing ground tab.[/QUOTE]
                The shield on the A B preamp connections provides the organ ground to the AO-28. The brown wire from the gnd terminal by the GG terminals provides the ground to the AO-39 and the reverb amp.

                Jim

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                • #9
                  It's alive and working. It was actually simple i just needed to remove the top board (6 screws -2 under, 4 on top ) then the wiring is very clear. As far as the vibrato the brown wire was cut very short at the capacitor box. Once replaced everything worked as intended. Now i need to do some woodwork the 2 sides are sawed off at different angles just below the generator. Is it possible to remove the sides and cut them cleanly or would it be better to add 2 side boards on top of the mangled ones.

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                  • #10
                    After reading the infos on this forum it looks like there is no short cut for the cabinet work. Either i leave the damage that was done alone or i remove the innards from the back, which involves desoldering the manuals from the generator.

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                    • #11
                      I've desoldered, removed, and reinstalled quite a few generators over the years. You need good desoldering equipment like a soldering station like a Weller or Hakko. Trying to do it with a 25W pencil iron will be very slow. You need a soldering station. I did one years ago with a soldering gun, which worked, but I had to take breaks when it got too hot to hold in my hand. Some people try to reattach the harness using the old, oxidized solder, and this frequently leads to bad solder joints and tones that drop out.
                      I'm David. 'Dave' is someone else's name.

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                      • #12
                        Thanks David, i have a Weller but i'm hesitating since this patient was amputated without anesthesia and miraculously recovered. The uneven sides are only a functional problem if the organ is on a table. I'm going to put it on a stand holding the bottom shelf so it should be leveled.

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