Vintage Synth Explorer Forums

EDIT: This thread relates to a DIY MS-20 external pot controller that I wanted to build, it's a simple build but for future reference I'll leave this thread to help anyone that's interested in building their own;


...Hi, I don't own one of these but would like to see what makes it tick to see if I can do something similar with DIY, if anyone has the schematics I'd very much appreciate it - free please not looking to shell out for this one.

Cheers

dont have the schematics, but there's nothing fancy about it. it's just an active pedal (batteries) with +/-4 V Output, and an attenuator (like the patchable vca on the MS20)

pflosi wrote:dont have the schematics, but there's nothing fancy about it. it's just an active pedal (batteries) with +/-4 V Output, and an attenuator (like the patchable vca on the MS20)

Yeah I know it's dead simple, but I need to know exactly how it's wired up - not so great on the old electronics theory and just an simple schematic for this would be a huge help

hmmm... take the MS20 service manual from http://www.synthdiy.com/pages/servicemanuals.asp

the pedal does the same thing as the mod wheel, only with separate outs for +/- (i.e. not bipolar as the wheel) and only 4V instead of 5V. It's just a pot (i.e. variable resistor).

The attenuator does the same thing as the patchable vca, with the control input hardwired to the pedal cv.

Maybe that helps a little bit...

pflosi wrote:hmmm... take the MS20 service manual from http://www.synthdiy.com/pages/servicemanuals.asp

the pedal does the same thing as the mod wheel, only with separate outs for +/- (i.e. not bipolar as the wheel) and only 4V instead of 5V. It's just a pot (i.e. variable resistor).

The attenuator does the same thing as the patchable vca, with the control input hardwired to the pedal cv.

Maybe that helps a little bit...

Hey, thanks for your help pflosi.

Well, I've got the schematic of the modwheel and I'm still a bit confused



I can see where the +ve and -ve voltage and the earth goes but what is the active of the jack (with the arrow) supposed to be connected to? I've had a look at the actual pot on the MS-20 and it seems to have 4 contact points, not the usual 3?!

What am I missing here? If you could draw up a quick schematic in simpler terms showing where all the wires should be connected that'd be great.

Thanks again.

I think it's a standard variable resistor, like this:



i don't think it's 4 pins... not sure though (maybe 4 pins for bipolarity?). i'm sure someone else can explain it better than me, i'm also not really a technician...

Edit: Ok, I have worked this one out.

Looked at this video, to get more of an idea on how it worked -




Right, so I've worked on it some more today and the 4th connector is actually a second negative connection to complete the circuit to the output, here is the revised design;



I've tested mine out with the voltmeter and all is well, straight sweep from 0 to +5 volts, happy days!

Thanks again for you help in this Pflosi,

will post pics of the completed project if anyone's interested.