Yamaha CS80

David mate,

Here's a thought:


So in therory, if you put all 7 triggers to 2 X 4019 and put it low -
6.5 say and join all the out's together and connect it to the trig 9 
wire. You should have your ringmod back....on paper. I think :)
I will give this a go tomorrow and see. 



--- In yamahacs80@yahoogroups.com, "David Rogoff" <david@...> wrote:
>
> --- In yamahacs80@yahoogroups.com, "billwolfer" <bill.wolfer@> 
wrote:
> >
> > Someone mentioned modding the CS80 to 7 voices if you have a 
dead or
> > troublesome voice. I just had this done, courtesy of David 
Rogoff, our
> > moderator and list-owner. One of the VCO chips was misbehaving, 
so
> > David asked me if he could change the keyboard circuit to 7 
voices. It
> > sounded like a reasonable, albeit temporary solution, but when I 
got
> > the machine home again, now the EG for the ring modulator is not
> > functioning. I know that this EG is monophonic, and that it was
> > working before the modification, so my theory is that by 
crippling one
> > of the voices, somehow we are bypassing the EG circuit for the 
ring
> > modulator. Can anyone verify this?
> 
> Here's the details on what's happening.  Based on the KAS chip
> datasheet, I changed the MODE pins from a one (-6.5v) to a zero
> (8.5v), which puts the chip in 7-note mode. A side-effect of the 
way
> the KAS works is that in this mode it jams the KO8 gate output 
active.
> This caused the 8th voice cards to drone, which I "fixed" by 
removing
> the VCO chips (one of which was bad, anyway). The other side-
effect is
> that the TR9 gate signal, which is an OR of the other 8 gates, is
> always on. This is the gate used to trigger the EG for the ring-
mod.  
> 
> If this was a longer-term fix, it would be easy to disconnect the 
8th
> gate buffer (IC8 / TR8 on the KAS board), which would remove both
> side-effects.
> 
> It is handy that the KAS chip can be set for any number of voices, 
up
> to 8, for emergencies like dead voice cards (and because it was 
also
> used on the 4-voice CS50), although the dead cards have to be the
> highest number voices.  You can disable, for example, just voice 3,
> like some poly-synths were able to do. 
> 
>  David
>