@dseltz i think there are tube hifi repair folks closer than 600 miles. ask around at audiokarma as well, maybe antique radio forum, but there are lots of fisher tube owners at AK. any competent tube tech chould troubleshoot and repair. you might end up removing a piece of it and sending it somewhere.
check this discussion out:
https://audiokarma.org/forums/index.php?threads/fisher-custom-electra-iv.822585/
good luck holmes!