A demonstration of the Hammond L-100 mods by Kon Zissis (searchable in the internet archive wayback machine). I found this tonewheel organ at a thrift store last winter and have been tinkering with it for the last several months to get it up and running.
Because I was only able to find one video demonstrating the vibrato chorus and none showing this overdrive mod, I thought it might inspire others to revive these spinets which I think are wonderful contraptions (within their limitations). Be warned, not only am I a clumsy keyboard player, but also very new to working with electronics. This video is not an instructional video of any sort. Be safe!
Vibrato Chorus mod - this involves moving a wire (see instructions) adding a capacitor, a potentiometer, and removing a resistor. The result is that you can mix the vibrato and chorus signal from the vibrato amp. It also adds some volume and brightness to the sound. The KZ mod has detailed instructions on additional modifications that can effect treble and bass response, but I stuck to the simple version. KZ warns that not including the capacitor can cause a thump, and I can confirm this is true! I wouldn't bother doing it without the capacitor. Also, there is a trim pot in the vibrato amp to adjust vibrato width which would obviously have an effect on this sound. I didn't bother demonstrating the vibrato chorus with "small vibrato" but that indeed sounds different (a bit smaller). I love this mod - when I first got the organ, I wasn't altogether sure what the vibrato chorus tab actually did other than make it quieter, now it opens up a wider range of possibility.
Zener Overdrive - The KZ instructions first recommend adding one diode, but they also mention adding a second to get more distortion. I tried initially with one, and found using two much more satisfying. The mod also involves a capacitor, switch, and potentiometer,
Some other cool things about this organ: It's very simple to put an effects loop between the volume pedal and the amplifier (where the white RCA wire goes) to further play with the sound. All that's needed are a couple of RCA adapters. Likewise, it's fairly easy to run a guitar or other instrument through the amp in the same RCA input, I think it sounds pretty good as a guitar amp, but keep in mind I don't own a fancy one with which to compare it.
Please check out some of the music I'm involved in on my channel and here: basidium.bandcamp.com/music