07-13-2014, 01:21 PM
Well, I'd do the dry chopstick probe and poke on switch contacts, resistors, could get lucky. Really old carbon resistors can really be had to find, so I would probably replace all of them that are used for the affected band. Of course it could be something else like a tube which refuses to work on higher frequencies, but you will find it sooner or later. More opinions will also follow.