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Microphonic Swell Pedal in B-2

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  • Microphonic Swell Pedal in B-2

    Even after replacing the electrolytics in my B-2's AO-10 preamp, there is still a significant amount of noise, and it seems to be coming from the swell pedal housing. If the housing cover isn't screwed on tight enough, this makes the noise worse. It's like an intermittent static sound. The sound decreases as the swell pedal is turned down. But then I noticed that when the pedal is pushed all the way up, there is a very audible thump. This happens in both the Leslie anything the line out is going to. I figured this might be a microphonic tube, and tapping V1 V2 and V4 all produced some kind of audible thump, so it was hard to tell which one it might be. However, tapping the pedal housing, or especially the arm that links to the pedal produces the most offensive noise. I've read that the swell housing can go microphonic, but I haven't been able to find what the cause or remedy would be for that. I have had to adjust the variable capacitor when it got out of alignment after removing the preamp to replace the caps.

    On a possibly related note - where the heck are the screws that hold the filter tray to the generator? My initial thought to take care of the noise was to make sure those were good and grounded, but it's hard to see where they are without lifting the manuals up. I hoped this might take care of some excessive crosstalk on certain tones too. Checked the preset panel screws, those are all good and tight.
    Farfisa Mini Compact V1, Fender Rhodes 73 Mk. 1, Hammond B2, Hammond L-102 "El Choppo", Hammond M-101, Hohner Cembalet CF, Hohner Cembalet N, Hohner Favor Combo, Hohner Pianet L, Hohner Pianet T, Hohner Symphonic 30N, Leslie 145, Leslie "430" (former 130 cab with horns and light show added), Nord Electro 3, and an entire village of guitars and harmonicas.

  • #2
    I believe the tray is soldered in place.

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    • #3
      If you just replaced the electrolytic capacitors in your AO-10, you may not have gone far enough in terms of parts replacement.

      However, inside the swell capacitor housing, there is a wire, usually green, that loops around the pivot shaft. In some cases, if this wire is rubbing against the pivot, you can get noise. Try to dress the wire in a loop that doesn't touch the moving parts.
      I'm David. 'Dave' is someone else's name.

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      • #4
        I think that green wire could have had something to do with the noise. I took your advice on dressing it, and that static noise has so far disappeared. The thump is still there when the pedal is fully depressed. I still have to change out the non-electrolytics in the preamp, those parts are on the way. A new 6SC7 tube (V4) is on its way too, just to try out, since I read on George Benton's site that these tubes are prone to static and noise.
        Farfisa Mini Compact V1, Fender Rhodes 73 Mk. 1, Hammond B2, Hammond L-102 "El Choppo", Hammond M-101, Hohner Cembalet CF, Hohner Cembalet N, Hohner Favor Combo, Hohner Pianet L, Hohner Pianet T, Hohner Symphonic 30N, Leslie 145, Leslie "430" (former 130 cab with horns and light show added), Nord Electro 3, and an entire village of guitars and harmonicas.

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        • David Anderson
          David Anderson commented
          Editing a comment
          I guess it's a good idea to swap tubes, but 6SC7s are getting so rare these days that you don't want to have to replace one if you don't absolutely have to.

      • #5
        I tried a Sovtek 6SC7 just for fun, and it still seemed to be just as microphonic as the original. What I did notice this time around though was that when that static noise reappeared, wiggling the tube around in it's socket seemed to remedy it. George Benton's website says that these sockets get "problematic as they get older," does that mean it needs to be cleaned, replaced, or somehow serviced?
        Farfisa Mini Compact V1, Fender Rhodes 73 Mk. 1, Hammond B2, Hammond L-102 "El Choppo", Hammond M-101, Hohner Cembalet CF, Hohner Cembalet N, Hohner Favor Combo, Hohner Pianet L, Hohner Pianet T, Hohner Symphonic 30N, Leslie 145, Leslie "430" (former 130 cab with horns and light show added), Nord Electro 3, and an entire village of guitars and harmonicas.

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