Vintage Synth Repair

Hi Snowleopard,
I am assuming you are referring to the 72 key model.
The aftertouch and key trigger systems are separate, so you can have one 
without the other. It sounds like keyboard contacts all right.
Could liquid of some sort have got in there? When a group of adjacent 
notes stop working then this is a common cause. If they are scattered 
about the keyboard, then it is time to strip and clean the whole contact 
system, accumulated dust build up over the years will start to affect 
more and more keys as time goes by.

Regards,
John.