It would help to post the serial number. I think this is a micro command system. Code F-9 could be a blown shunt field fuse. The fuse should be a small glass (10 amp ? ) located in the rear panel upper right corner. The wire number should be 34. I would look there first and inspect wiring from it. Sometimes replacing the fuse is all it takes. Post your results and let me know if you need more information to dig deeper.