I've had a lot of requests for the schematic of the sequencer I used in my MS-20 mini mods. I've been very busy, but I finally drew them up all nice and perdy.
The circuit is a super simple one based off the 4017 decade counter IC. The clock input can be from anything with a pulse like the MS-20's square LFO, Volcas, drum machines, ect. I didn't hook up the reset due to lack of space on the MS-20 mini's chassis. This circuit gives you a gate and CV output for fun step sequencing.
The 4017 is powered by the 9 volts inside the MS-20.
Here is a Larger Image.
I admit that this circuit is very rudimentary and additions can be made to add more features. You can add jacks to each step so you can change the length of the sequence using the reset line. So many possibilities.
I added switches on mine so you can choose to engage or disengage the gate for individual steps for fun rhythms.
I also want to add a portamento switch that engages a portamento between steps. I'll document this when it's done.
If you want to get really fancy, you can throw a microcontroller into the MS-20 and read off the MIDI from the MIDI port and get clock signals to MIDI sync you sequencer. Leave a comment with any fun additions you do.
In other news, I have resigned from Ernie Ball / Music Man and accepted a job in San Francisco with Quirky. I want to get involved in the synth scene here. I am pretty sure it has to be bigger than SLO's. Let me know if you life in SF and want to make music or need repairs or anything.