The mod involved lifting one end of 9 different resistors, soldering a wire to each end and another wire to each point where the resistors were attached. Not rocket science, I'm just inserting a switch between each signal. Using ribbon cable was the hot ticket anticipating the wire soldered to the switches had to be of fairly high gauge (thin) due to clearance issues. Also this allowed for an easy way to disconnect/connect the analog board from the switches in the future without having to remove the left panel board, jack board and switches.
I was originally going to wire the switches such that for each VCO the down position is off and the up position enables all 3 mod sources. I then thought it would be much more flexible to have the down position select the external CV jack and the up position select the 2 bus mod sources. In the down position with nothing plugged into the external waveform CV jack, modulation is effectively disabled for that VCO.
Once the switches were wired up the fun part began; drilling the holes in the front panel at just the right point. It may be hard to tell but those switches had to fit between the Waveform pots and the Octave pots located directly above. I erred on a slightly higher vertical placement knowing I could cut away part of the metal shroud covering the Octave select pots if need be. Good thing as I did end up having to shave off about an 1/8th inch. If I screwed up and placed them too low the switches would be interfering with the waveform select pots (i.e. really screwed).
As a bonus mod I also was not happy with the waveform selection range. I recently watched a video where the presenter criticized the sawtooth wave not lining up with the knob graphic. I really couldn't care less about this since I always go by sound. But turning the waveform knob fully clockwise with no modulation did not result in a narrow enough pulse-width. IMO the sound should just completely disappear or at least "crackle".
I lowered some resistor values after going through a selection process for each one. I could have used trimmer pots but I didn't have the right values on hand and soldering on an additional resistor for each waveform select signal in parallel was easier to install. Anyway it appears that the knob position for a sawtooth waveform now lines up with panel graphic (woohoo).
