[sdiy] GEM / GeneralMusic SX-3 service manual

Roman Sowa modular at go2.pl
Mon Jul 16 10:53:20 CEST 2018

Don't know about this particular GEM, but for example Roland C-200 uses 
7-pin DIN socket for their dedicated pedals. It carries pure MIDI on 
regular MIDI pins and power supply on additional ones. May be similar in 
this case. I'd send some MIDI there to see.

The only other type of pedal connection I've seen in organs was bare 
matrix entry with 12 lines on DB15 socket.


W dniu 2018-07-15 o 21:02, Rutger Vlek pisze:
> Hi Brian,
> I know, beautiful thing, a switch matrix. This works differently though. 
> I've been able to identify the pinout of the plug and it carries two 
> types of grounds, one for shield and one for power. It carries a +5v 
> supply line and provides an Rx data input pin. So the original pedal for 
> which this input was designed must carry some active electronics. I 
> haven't yet nailed how they would gave done timing of the Rx channel. 
> Anyone fancy a guess at what would have been in there?
> Rutger
> Op zo 15 jul. 2018 20:34 schreef <rsdio at audiobanshee.com 
> <mailto:rsdio at audiobanshee.com>>:
>     You only need 11 or 12 pins for a matrix to support a 30-note pedal
>     board. How many lines on the DIN plug?
>     Brian
>     On Jul 14, 2018, at 1:25 AM, Rutger Vlek <rutgervlek at gmail.com
>     <mailto:rutgervlek at gmail.com>> wrote:
>      > Additionally, another question for GEM conaisseurs: there's a
>     pedalboard input (looks like a DIN-variant plug) that seems intended
>     to be used with bass pedals. Anyone know which type of pedals could
>     connect to this? Or what the control protocol is? I'm suspecting
>     it's either a straight diode-matrix-scan input (but don't think
>     there's enough lines to make up the required notes), or
>     communication line to some kind of multiplexer or shift-register
>     internal to the pedals. I have pedals from another brand here, with
>     straight switch-outputs and I'd love to modify it to work with the Gem.
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