[sdiy] Adding sync to dual oscillator Yamaha CS synths

[Richard Atkinson]

Hi all,

I've been growing tired of the wimpy sound of my Yamaha CS-15D. Apart from 
adding extra controls for Channel I, I thought I'd have a go at adding 
oscillator sync.

Has anyone ever tried this before? I'm not aware of any CS series 
instruments that have it as standard, but it looks like it might be 
possible. I had a look at the Yamaha IC Guide Book:

http://www.loscha.com/miller/Yamaha_IC_Data_Book.pdf

iG00153 VCO III is on pages 35 & 36. It looks like the VCO integrator 
capacitor at pin 14 of the first VCO could be discharged to GND by 
connecting a transistor across it, controlled by the one-shot 
multi-vibrator waveform at pin 10 of the second VCO. The waveform actually 
available at pin 10 of an iG00153 may need some buffering and/or inversion 
to perform this task, but it strikes me it should be possible.

Richard