Repeating VCF A(S)R Modification

This modification creates a repeating envelope generator that can be used like an LFO with adjustable wave shape.

Parts Required:

1) DPDT (center off) miniature toggle switch

1) 1N4148 or 1N914 signal diode

3) 10 K resistors

1) 1 K resistor

1 - 2’ length insulated wire

Procedure:

Remove the wire jumper 9 near point M .

Replace the jumper with a 1N4148 or 1N914 diode.

Tack solder a 10K resistor between pins 3 and 14 of IC8.

Cut the circuit trace connecting pin 8 to V REF (Pin 11, resistors R85 and R86) on IC8.

Install (tack solder) a 10K resistor between pins 8 and 11 of IC8.

Tack solder a 1K resistor between pins 7 and 10 of IC11.

Using insulated jumper wires, make connections between pin 14 of IC8 to pin 12 of IC11. Make connections between pin 8 of IC8 to pin 11 of IC11.

Install a DPDT (center off) toggle switch (RS 275-1545 or RS 275-664) in place of the switch installed at S3, the A(S)R sustain switch.

Connect wires between the following:

Lugs 1 and 4 of new S3 to lug 1 of R115

Lug 2 of new S3 to wiring point (M)

Lug 3 (thru a 10K resistor) to R79 end, nearest to Q7 (junction of R79 and Q7 base).

Lug 5 and the O15 end of R79

Now the A(S)/AR switch functions as an A(S)R/AR/Repeat AR switch.In the down position, the A(S)R mode is selected. In the middle position, the AR mode is selected. The up position selects Repeat AR mode.

Many, many thanks to Scott Lee for creating this design.