Korg MS-20 Teardown: Pulse Width Modulation Install

The vintage Korg MS-20 monophonic synthesizer comes with a pulse width knob, but no way to patch a modulation to it. In this video I teardown the MS-20, and install a Pulse Width Modulation routing.

My PWM will come from the MG/T.Ext circuit that is already present on the synth. 90% of the time I want to use the MG, AKA the LFO, to modulate the Pulse Width. So all I will do is add a small pot and current limiting resistor for routing the MG/Total circuit to the Pulse Width.

What about the other 10% of the time I don't want MG going to PWM? Well the MG is only normalled to the Total/External jack. If something is patched into the Total jack, it will override the MG and be routed to the new PWM pot. It behaves exactly the same way as the MG/Total pots for Pitch/HPF/LPF. Pretty sweet.

At the end of the video I patch various things to modulate the Pulse Width. Stay safe, don't electrocute yourself, and be sure to unplug the synth at all times while doing work inside the unit.