No help, or too expensive?
Tannewitz had the actual build manual for my RAMCO almost 15 years ago so that was good for air and electric schematics.
However,the most useful manual was from Howard Grivna "Principles of Widebelt Sanding and Data Reference" Outlines the principles and practice of setting up & running any widebelt sander. Really nitty gritty. Trouble shooting. etc. At the time, it came with at least 1 hour of direct phone time with Howard. He was businesslike in the sense of not wasting your time or his, but i'm not sure he kept close tally of the cumulative time if you seemed to be using it well.
Sanding Systems Inc
Someone on OWWM reported he may be in a home, so i don't know if the above link is active.
Carter Products appears to sell/resell copies.
Principles of Wide Belt Sanding & Data Reference | Carter Products
smt