Just a tip for anyone thinking about modding the synth to make osc 2 syncable to 1... Use shielded wire from the board to your switch+diode and ground it (i soldered the copper shield to the side of the range select switches). Otherwise when the sync switch is off, osc 2 will still lock on to 1 when they are tuned close to each other due to capacitive interaction (so you can't do that chorusy 2 osc sound). A thin RCA cable works fantastic.