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Thoughts on the Hammond Vibrato Scanner

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  • Thoughts on the Hammond Vibrato Scanner

    Just thinking out loud ...

    Having recently overhauled my vibrato scanner to resolve a ticking issue (caused by a sticking issue), and having been very careful to not bend the little pin through which the signal flows out of the scanner through a set of triply redundant (presumably for reliability and noise reduction) "brushes", it occurred to me that Hammond could have made the scanner completely brushless.

    The rotor of the scanner has a set of plates on one end that revolve through the sets of stator plates to scan the line box, a shaft and the aforementioned pin in the middle, and a counterweight at the other end. The pin protrudes from the scanner into another compartment on the back of the scanner containing the brushes.

    My thought was that instead of the pin, there could have been a stack of circular plates (say 5cm in diameter) on the shaft, and another stack of fixed circular plates that these mesh with in what is currently the brush compartment (which would need to be relocated to the centre of the scanner back, and maybe enlarged). This fixed stack of plates would need a slot cut in it for assembly. The output signal would then be capacitively coupled from the rotating circular plates to the fixed ones. As these plates would be much larger than the stator and rotor plates, their capacitance would be higher, and so would not significantly affect the signal (and what little effect they do have could be compensated for in the vibrato amp).

    This would have made the scanner much more robust IMO, and probably not significantly affected the cost, since less precision is required than with the current pin arrangement.

    This is also a viable DIY idea, and might be a way to rescue a scanner with a damaged or broken pin.
    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
    Is this a project you intend to pursue or are you just throwing it out there as an idea? Either way, IMHO i think Hammond wanted the simplest methodology to bring the signal out of the scanner. I've always been impressed with the company's mechanical engineering as well as their electronic, and having serviced and rebuilt hundreds of scanners over the years, I can't recall an issue with the brushes. I do, however, feel that the pin could have been a tad beefier. That being said, if your idea provides a better scheme for bringing out the vibrato signal, perhaps one of the talented engineers on the forum will tackle it.
    Over the years: Hammond M3, BC, M102, B3, four X77s and three PR-40s, a Thomas Electra and a Celebrity, three Fender Rhodes, Roland HS-10, HP-2000, HP-600, RD-600, JV-880, a thing made by Korg (?), two Leslie 910s, 122, 257, 258, 247, two 142s, and three custom-built Leslies. Wow, way too much money spent!

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    • #3
      I would pursue it if I didn't have a zillion other hobby projects, including many involving my Hammond organ, so I just tossed it out there for discussion in case anyone else wanted to try it.

      I can understand why they made the pin as thin as possible. If the pin were twice the diameter it is now, then it would have twice the contact area and thus twice the linear friction, resulting in twice the wear. It would also have twice the leverage trying to slow the scanner down, so combined with the friction, require quadruple the amount of power to keep the scanner turning. And, I may be wrong about this, but it might also require twice the spring strength to ensure the brushes maintain good contact, which would further double the wear rate and friction. Furthermore, making it only twice as thick wouldn't even really be enough to make it strong enough to resist being bent.
      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


      • #4
        Of course, if someone had a scanner with a broken pin they'd want to send me, I could try to fit it in over the winter. :-)
        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

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