http://www2.yamaha.co.jp/manual/english/menu_f.html
This is a place where you can signup and download Yamaha manuals, even for
ancient stuff. I just pulled down some manuals for gear that I own, and got
a GX-1 manual too just for some light reading.
I found this site from another great site - Combo Organ Heaven:
http://rodak99.tripod.com/
Very cool stuff!
Ivan