[sdiy] Yamaha SY-2

[Richard Atkinson]

Hi Martijn,

Very interesting! I'm told that if you leave it on for too long
(around 20 minutes), the pulse width control stops working, and all
the presets that use pulse control (around a third of them) stop
working. All works fine for the first 20 minutes you have it on, then
you can just let it cool back down, or use the other 2/3rds of the
presets.

My main plan for this synthesizer involves replacing one of the
presets with variable controls. The service manual gives full details
of the resistor/diode matrix for the presets. By replacing one row of
these with switches, diodes and variable resistors, I hope I can get a
fully variable SY-2 sound.

Richard

On 4/25/07, Synthusiast <synthusiast at gmx.net> wrote:
> >Hopefully the problem with the pulse wave output will turn out to be in the
> >external components and not in the epoxied modules!
>
> Interesting. I had a SY-2 here a few weeks back with the same problem. It
> turned out that the offset of the sawtooth output (from the epoxied
> module...) was several volts high. This caused the pulse waveshaper, that
> runs on the sawtooth output, to stop functioning. The offset couldn't be
> trimmed away, so I put a small capacitor between the sawtooth output and the
> pulse waveshaper input. Worked like a charm.
>
> Regards,
> Martijn
>
>
>