You probably won't have much luck in this forum as most of the techs here work on acoustics and are not electronics wizards. I did have some luck getting some drawings and schematics for a mark 15 DP from the Young Chang reps in Canada. There is an association of technicians (MITA) that service organs and DP's but many, if not all, have turned their backs on Kurzweil. They had extremely poor response for parts and had to wait for a long time often getting the wrong ones ect...
Seems like the waters got murky when YC almagamated with Kurzweil on these instruments. Schematics however may be sitting in some computer and if the techs don't want to muck with it themselves, they would likely be kind enough to share it with you if you ask.
You may want to dig around at the MITA site. I have a good association with one of their techs in my region who has often helped me out aquiring info on DP's and organs and such.
http://mitatechs.org/public_splash2
