Archive of the former Yahoo!Groups mailing list: Discussion about the Korg PolySix synthesizer

Here are a few more observations/measurements. Feel free to correct:

Pin 2 on IC14 gets the control voltage for the MG delay; the range is
between about -4.6V (Delay 0) and +4.6V (Delay 10).
Pin 3 on IC14 gets a voltage that is "ramped up" from -5V (to about +13V).
IC14 then acts as a comparator/Schmitt trigger, changing its state from
-15V to +15V.

So basically if the voltage on Pin 2 is very low (Delay 0) the ramp on Pin
3 will cause IC14 to switch immediately or nearly immediately. However if
the voltage on Pin 2 is higher the switch will occur after some time has
passed and the voltage on Pin 3 has gotten higher.

The ramp on Pin 3 is reset with every NEW gate signal coming from KLM366.
As long as keys are held no new gate signal is happening; for a new gate
signal all keys need to be released first.

What is happening with the clone is that this reset doesn't always start
the ramp at -5V; sometimes the reset doesn't reach the full depth and the
ramping starts around +2V or so. Which of course means that IC14 switches
it's state earlier than intended (because the ramp takes less time to reach
the "switching point" since it didn't start low enough).
This leads me to believe that C33 isn't fully discharged.