Microphonic A100

[analogtodd]

Hi
Been working on a couple of A100 organs. One of them appears to be microphonic. With all the draw bars in, no perc on, no chorus on, with no presets on, you can tap on the keys or plastic end caps or even just the wood itself and it rings like its microphonic. This particular A100 has no speakers or power amp or reverb amp, just the AO28 preamp.

I chalked this up to being a microphonic tube, but I swapped out the whole set from another AO28 preamp, and the microphonic sound is still there. I finally thought, maybe I had a bad cap or something in the preamp, and I yanked the preamp out and replaced it with another AO28 preamp (which sounded fine in the other A100 cabinet) and it still sounds microphonic.

Is there something in the cabinet or Tone Generator that can be microphonic???? I've thumped around and tried to isolate, but so far, nothing good.

[analogtodd]

Ok, not more than 2 min after writing this, I went and tried again, this time, I noticed the Perc Line Transformer seemed to be where the microphonic sound was coming from. I pulled the cover off, wacked it a few times, ran a Han-D-Mag over the cover and the transformer and the preamp for good measure, and then I fired it back up. Its about 500% less microphonic now! I just saw a post while searching microphonics where someone said they'd used grommets to isolate the transformer even more, I think I might do that too! Thank you forum! :)

[Papus]

My T202 sometimes goes microphonic......... it's the actual tone wheel pickups themselves......... when I crank it through a Marshall Plexi half-stack pushed by a Tube Screamer pedal :P