[sdiy] Electronic organs revisted: using organ manuals and pedals for synth DIY projects, etc

[aankrom]

So I'm looking at the shcematics for the Kimball 600 organ that I am 
going to cannibalize. The upper manual looks like the best candidate for 
synth projects because it has more switches per key. Still the lower 
manual and the pedal board look promising. All that wire is a little 
daunting. I guess it's a good thing I'm not trying to fix it.

What I am curious about is anyone else who has done this sort of thing. 
The keys and the action on the manuals are actually pretty good. I'm 
just not sure which keyboard scanner circuit is the best to use I'm 
going to check MFOS and CGS. For the pedal board I'll probably use Ken 
Stone's circuit that uses a 74C922: I have a a 74C923 which I hope is 
easily adaptable. I also have an old Popular Electronics magazine from 
1979 that shows how to expand key-count of 74C922's using a few 
74LS367's, which I happen to have a ton of. (I just do. Heck, it's crazy 
that I just happen to have 2 74C923's just sitting in my parts bin.) 
With the 74C923 I should be able to have a 20-note keyboard. Or maybe I 
could just not use on of the pins and use it like a 74C922.

If every tone on this organ didn't sound like some sort of squarewave, 
I might fix the ciphers and dead notes, but there's a lot of nice 
Sprague orange drop caps, lots of good wire, lots of 2N404's.

Plus the speakerbox I have to move the amp and reverb into is sweet - 
great sound board. The power supply for the organ uses FOUR chokes and 
there's a big coupling transformer between the preamp and the power amp 
- it could be for phase-shifting, but it has a lot of leads, well six 
instead of five.


Incidently, I fixed the rhythm section and have drawn up some plans to 
make it into a stand-alone unit that still uses some wood from the 
organ. I want to modify the unit so I can trigger each sound independent 
of the rhythm generator. I'd also like to be able to tweak the sounds 
just a little bit. I can see this project getting easilly out of hand. I 
just want a cheesy rhythm machine like the old Rolands or Korgs. I 
already have a Boss DR-660 and two Coron DS-8 clones. One weird thing: 
the tempo changes if you disconnect the lamp that flashes on the 
downbeat, I'm guessing it's because the lamp is incandescent and the 
load it presents affects the tempo. I'm still poking around the circuit 
with my scope and DMM (wish my analog MM worked...) to see what's what.

AA