Vintage Synth Repair

Does somebody have Service Manual for this MIDI master keyboard V  
3.0? I just bought one (Japanese production), cleaned it and  
restored, everything is OK, I just like to have a Service Manual for  
the future reference.

It's an unbelievable technology. miracle of engineering,  and yet so  
simple solution. I'd like to know more about that key switching  
system, how it's done. There's only one contact and it can send  
initial and release velocity plus polyphonic aftertouch.

Thanks in advance for any hint or info.

Daniel Forro