Fixing things sometimes involves trying to loosen screws that won't turn. This is a method that works as long as you can access the sides of the head of the screw. In this case it was the screw that secures a plastic gear to the tuner. The tuner wouldn't turn due to corrosion. Forcing the gear risked stripping the gear where it fitted onto the tuner's metal axle. Penetrating oil and vinegar had no effect. Since the screw head was flush with the surface of the gear, I cut away enough plastic to be able to grip the sides of the screw head with wire cutters. The plastic removed has no effect on the function. The screw then came out. I was able to grip the tuner's exposed axle head in a small vise and free up the tuner. I don't know yet if the tuner works. Edit: Later, the tuner works. Amazing.
About the slide switch next to the tuner. I've found spraying such switches with cleaner/lubricant is inadequate. This leaves too much tarnish and contaminants to ensure reliable operation. I remove and disassemble them to clean them properly.
Can you get a small impact driver with JIS bits on that screw? Project Farm is the best for tool testing, this one is for penetrating oils
I don't have that sort of equipment. I got the screw out, the plastic gear off, and the tuner freed and loosened up. Installed it in the J9 I'm trying to restore radio audio, and in addition to other repairs, the tuner works. I have another J9 tuner that was corroded, frozen and now freed up. No sense even testing it. It will go back in the corroded J9 it came from, that has so much wrong with it and has been so thoroughly pillaged for good parts that it will never work again.
It often helps to warm up the screw slightly with a soldering iron. But be careful not to melt the plastic tho. Mechanics do the same with seized bolts, for example on a car. It is best to keep liquids away from variable tuner capacitors. Especially the small ones found in radios. As soon as moisture gets in, the alignment goes completely wrong.
