Hammond L100 - noisy harmonic tabs

[Roomorchestra]

Hi all,
When I depress either the 2nd or 3rd harmonic (or both) percussion tabs, my organ makes a lot of noise - a loud swishy white noise. It goes or is severely lessened when I take the percussion off. Any ideas what could be the cause? There's also an increase in a ground hum sort of noise when I turn the volume / expression pedal up over half way - normal?

Thanks,

[geoffbrown]

Sounds like your amp needs an overhaul, a good starting point would be replacing all the electrolytic capacitors if they are original

[Roomorchestra]

Yeah, that sounds about right - they do all look original, apart from the run capacitor which I replaced a few years back.
I'm not sure about doing these sort of repairs myself, but there's no one I can find in my area who will repair it (esp. at the moment of course). So far I cleaned all the valve bases, RCA posts and the square plastic connectors with a contact cleaner, and the noise from the Perc. Tabs did seem to get a bit better - temporarily. I can use it as it is, but it'd great to get the percussion working again.

[theseacowexists]

It sounds crazy, but run a ground wire from the chassis of the motor to the chassis of the generator. Instantly cleared up the percussion tab static for me.

[Drawbar Dave]

Clean your molex connectors too!

[Roomorchestra]

Thanks all. Yes, I have cleaned the molex connectors - but I think I could give them another going over with the ol' de-oxit.
@theseacowexists:Forgive my ignorance, but in terms of running a ground wire from the chassis of the motor to the chassis of the generator -is it just a simple bit of wire soldered between two points, if so what is the generator...

Thanks again.

[theseacowexists]

Yes, it is just a simple bit of wire soldered between two points. You don't necessarily even need to solder a wire, an alligator clip lead will work just as good and is easier to install (and uninstall!). The generator is the tonewheel generator - the big metal thing that sits below the top shelf of the organ and is about as wide as the organ.

[Roomorchestra]

Brilliant. Thanks for the tips. If you don't mind, I'd be interested to know why this works - how come the ground wire cleans up the noisy percussion? It just earths something in the signal path I guess?

[theseacowexists]

Roomorchestra
Yes, it must just earth something in the signal path. I also had a T-200 that made that static noise no matter what setting it was on, and this trick cleared up that noise as well. Too bad it couldn't clean up the mechanically noisy vibrato drum scanner :/

[Roomorchestra]

Yeah that makes sense - I see how that can work. Unfortunately it's not solved the issue in this instance - I tried earthing the signal path between the motor and the generator using a crocodile/ alligator clipped wire - but the perc. tabs are still making the same noise when switched on. I've also cleaned the Molex connectors (at least I think I have - several times), and that's not cleared it up either.
Hmmm. It's weird because the noise goes as soon I depress any keys, but it's pretty unbearable in between the notes, and it cuts the attack effect off when you play a note. I'm a a player and performer (as opposed to a engineer) and it's a shame when recording I can't use the percussion. It's an immaculate L122 and a shame I can't get to resolve this, as it's a great playing organ in all other respects. Thanks to everyone here on the forum though for the suggestions.