I see you have no responses so far on trying to access your converter on this old coach. I'll be honest, I dont have a clue either but just for fun I was reading some other owners comments on their old Pinnacle coaches and one of them said there are four plastic caps on the entry steps that cover screws which hold a cover plate over the converter. If this is true it might apply to your coach too. I was reading this info at
Hope this helps you a bit. By the way they said that schematics etc are very hard to come by.......but maybe they are still around that you can contact since it was 2011 posts I was reading. Good luck.