Thanks, Johnar, but that is not the one for my model.
Mine is called an "AH + 2" and was made in the early 90's. It has a rectangular LCD screen and lots of dip switches on the back. It seems to work but I have no idea what the dip switches do.
Phil,
I've got the manual (18 pages with schematics). I'll be away from the computer for a few hours so PM me at draganaba@earthlink.net if you haven't found another source.
Andy