Vintage Synth Repair

So I dusted off a TX802 rack module and it seems to have a very odd 
response on the Envelope Generators: Notes die too soon, and at 
irregular intervals. The cut is abrupt and sudden, and ignores any 
performance, voice and setting I can come up with. The unit otherwise 
seem to be behaving well.

Any help appreciated. A service manual - or a copy of it, would be 
grand.


Thanks,

Mu