Welcome to the forums!
I don't know of any schematics for your specific unit. However it is fairly easy to figure out, just turn everything on, then pull one fuse at a time and see what shuts off.
Attached is a copy of the Owner's Manual which may help you out a bit. Given the age of it I would seriously consider replacing it in the not to distant future. The newer 4 stage converters are a whole lot better and easier on the batteries.
I would use a Progressive Dynamics from
Best Converter.
Aaron