CS-50 CMOS, and "C50 Taurus" Idea

[Haible Juergen]

> Do you have advice on where to start?

All right, I've opened my CS-50 last night. The chip I replaced is IC2
on the left pcb under the keyboard.
No idea if this is your CS-50's problem, too, but then there are really only
a few CMOS 40xx chips there at all. (Check the right pcb under the keyboard,
too.)

Now, when I went thru the schemos last night, another idea struck me.
Ok, there is this method of pseudo-unison playing, but you need an external
device to shape the envelope then. I used a pedal so far.
Next step would be to bring out a GATE signal and control an external VCA.
What you need is a GATE that is active when *any* key is depressed.
(Not just the individual voices' gate signals). Should be easy to derive
an overall GATE from th eindividual gates, but - nice surprise -
such a GATE is already there. It's called "TR9" (diode-OR-ed from TR1 ...
TR4),
and its used to trigger the envelope of the Ring Modulator.
So I just need to find a place where to retrofit a GATE OUT jack. (not easy
with all this thick wood)

Next step would be to build an external VCA - or use a VCA from a modular
system.
Then why not also use an external VCF. 
Now which VCF / VCA combination is most famous for Bass sounds ?
You guessed it. I always wanted to build the VCF / VCA part of the Moog
Taurus,
but now I feel motivated to start the project. The V/Hz VCOs of the CS-50
would be a worthy input for a Taurus backend, I think.

JH.