Heathkit AP-1800 Preamp right channel quit working

I have a Heathkit AP-1800 preamp that the right channel quit working. I have a schematic but need a service manual and operators manual. Even a build manual would be helpful. Does anybody have one of these manuals they could scan and send me or a manual I could buy? Any thoughts on what might be wrong in the preamp? Thanks.
 
Jon. Thanks for your reply. I actually found a manual that is 140 pages long. That must be a build or service manual. I can’t imagine an operators manual being that long. I am ordering it today and will see what it is. Anything will help.