Vintage Synth Repair

I couldn't find anything on the web except those that cost a lot so
I'm wondering if anyone could provide some schematics .pdf or .jpg for
my arp omni since I need only the sections for the lower and upper
voicing boards, especially the part for sustaining, if possible with
some description which sections on these boards relate directly to the
keyboard. A complete schematics in .pdf or jpeg format would be great
too. Thanks for helping.