1. Increase range of Frequency knobs.
Cut ground wire from pin 3 of pots R86 and R88 ("Freq" knobs). Attach 10k resistors here. Connect other ends of resistors to pin 3 of pots R85 and R87 ("Q" pots). So, R86 pin 3 resistor to R85 pin 3, R88 pin 3 resistor to R87 pin 3. Then, replace R47 and R48 on the board with 10k resistors.
What this does is to sweep between negative voltage and positive voltage instead of between negative voltage and ground, and with smaller resistor values at the ends of the pots, which altogether increases the range of the filter sweep just right.
Note for this mod: with cutoff opened up and resonance set high, a high control voltage signal may create a loud clipping which can make the unit seize up and stop working until power is turned off and back on again. years of use and still no damage though!
2. Stop Modulation from controlling frequency.
Cut wire that goes from pin 2 of pot R89 (Modulation Output) through 2 resistors on to J9 and J12 ("Fc1") switch lugs. You can remove the resistors if you want.
3. Stop Fc2 of Filter A from controlling Fc2 of Filter B.
Cut wire connecting J10 and J13 ("Fc2").
not responsible for any damage or injury.