Here are some mods I have used on the PCLONE2. I am not an expert on analog electronics so these were mainly found by educated guesswork, trial and error. I am always grateful for new ideas or ways these mods might be improved.
This is a very simple mod where we apply the CV directly to the point where the LFO modulates the VCO pitch. We use a resistor (I used 100k) so the CV is mixed with the signal from the LFO and voltage from the pitch control/sweep circuit. This is NOT a tuned CV (no 1V/octave or anything!) and you may find that you need to use CV’s within a narrow part of the full voltage range for the pitch to be affected usefully. However, for just a resistor and a bit of wire, this is a nice mod. I may try to refine it at a later time (in particular to expand the useful voltage range)
Solder a 100k resistor to the top pin of an unused CV socket. Solder a wire to the other end of the resistor
Connect the other end of the wire to the left tab of the DEPTH pot. Done!
Calling this a “Decay CV” might be overstating it a bit, but this is a quick mod that can give some nice rhythmic variations when used in a sequence. Basically the CV is used directly to charge the capacitor (C8) that controls the VCA decay and the pitch sweep. We use a diode to prevent any current being sunk by the CV connection when the voltage is lower than the output of the trigger circuit. This relies on your sequencer having a fairly low impedance CV output and you should experiment with different pulse lengths and voltage levels, and also with interactions with gate pulses to the main trigger input.
Solder a piece of wire to the anode (stripe) of a 1N4148 small signal diode
Solder the other side of the diode to the top pin of an unused CV socket
Connect the other end of the wire to the hole above the SENS and DECAY terminals
Solder it from the back and trim the solder joint. Done!