Need radio's most “honnable” model “numbah” for further researching, (if required).
Otherwise, I'm considering the age to be borderline on mechanical versus electronic switching, giving the consideration now. . . . . as to it being mechanical switching.
And I would take a very educated guess that you very likely never even got close to the contactive innermost workings of that switch mechanism, unless the radio was pulled and the dust covers dropped to fully expose the switch mechanism.
Then, to be sure, I put a drop of refrigeration putty (or childs modeling clay on the topside of the switch) (metallic chaff control) and then just barely drill a 1/16 th inch hole topside of the control. This positively permits solvent flooding within the switch cavity.
Then the switch compartment is flooded, via that access hole, with “Radio Shack” tuner cleaner, that has its plastic tube mated with an insulin syringes ***small needle. (Rolling on of plastic tape onto the basic tuner cleaners plastic “extension “ spout/tube will interface the two plastic pieces different sizing.
(***If you have medical supplies access…a # 17 needle, on upwards in size numbering. . . . .will result in faster flow than the insulin syringes small needle sizing. . .but more people probably have free access to a diabetic relatives cache of syringes. )
Then rapidly and vigorously work the switch ‘bout one hunna ‘lebenteeen times and then check out that switch for repetitive continuity.
ZUJ'ing for feedback. . . .
73's de Edd