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On dealing with a broken tab switch in an M-series organ

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  • On dealing with a broken tab switch in an M-series organ

    I was just doing some maintenance and cleanup work on my M-111, tidying up the various projects I've done on it over the years (see my signature), and fixing a few snags.

    One problem I was fixing was that when activating the 2nd harmonic percussion, the percussion worked, but the 2nd harmonic disappeared from the registration (if it was being used). I quickly traced this down to one contact in the 2nd harmonic switch. Attempting to clean an realign it didn't fix the problem, so I decided to work around it.

    The tab switches each have a pusher that comes out of the back when the tab is depressed, so what I did was fashion a small extension to the switch frame, to which I attached a lever-style microswitch to be depressed by this pusher. Since a picture is worth a thousand words ...



    I then wired the normally open contacts of this microswitch to bypass the offending original switch.

    This technique can be used to repair many, but not all, of the tab switches. Some of them have interlocks on the back, which is actually what the pushers are there for, so there'd be no room for a microswitch. If you need to bypass multiple contacts, the switch could control a relay, and the relay used to bypass the contacts.

    BTW, an interesting thing I discovered, initially by tracing the schematic, and then confirmed in reality, is that if you've got both 2nd and 3rd harmonic percussion selected, pulling out either the 2nd or 3rd harmonic drawbar gets you both harmonics.
    Stefan Vorkoetter: http://www.stefanv.com

    1962 Hammond M-111 with Improved Vibrato, Internal Rotary Speaker, Drum Machine,
    Window Seat Tone Cabinets, Completely Rebuilt Amplifier, and Recapped Tone Generator.
    1978 PAiA 1550 Stringz'n'Thingz with many enhancements.
    2017 Raspberry Pi organ-top synthesizer.

  • #2
    I must write to you finally that I have followed your renovations and improvements for several years. You never fail to amaze and inspire with your ingenuity and craftsmanship. In fact, though I am an old Hammond salesman from the '60s and '70s, you have given me the courage to tackle many projects, including my current BV from 1948, that I would not have normally attempted.

    I recapped the gen and line box, preamp, and rebuilt a nearly trashed black painted 22H leslie, including replacing some cabinet parts.

    Thank you for your inspiration.
    Larry K

    Hammond A-3 System, Celviano for piano practice
    Retired: Hammond BV+22H+DR-20, Hammond L-102, M-3, S-6, H-112, B-2+21H+PR-40, B-3+21H, Hammond Aurora Custom, Colonnade.

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    • #3
      This seems to be a common problem for M100 owners, it's happened on my M100 but until now I haven;t tracked down the cause of the problem,thank you for this excellent post

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      • #4
        Thanks for the kind comments.

        Originally posted by stefanv View Post
        ... the various projects I've done on it over the years (see my signature) ...
        Hmmm. It appears that my signature has vanished, and I don't see anywhere to reinstate it.
        Stefan Vorkoetter: http://www.stefanv.com

        1962 Hammond M-111 with Improved Vibrato, Internal Rotary Speaker, Drum Machine,
        Window Seat Tone Cabinets, Completely Rebuilt Amplifier, and Recapped Tone Generator.
        1978 PAiA 1550 Stringz'n'Thingz with many enhancements.
        2017 Raspberry Pi organ-top synthesizer.

        Comment


        • Admin
          Admin commented
          Editing a comment
          I see your sig. It doesn't appear immediately on a new post without a page refresh, but it should be present on older posts.

        • stefanv
          stefanv commented
          Editing a comment
          Thanks. I don't see sigs on anyone's posts. Very odd. Also, I don't see anywhere to edit it under User Settings, Account.
          ... Never mind ... I found a little tiny checkbox that says "Show Signatures".
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