I agree with David, spray some tuner cleaner, or even Old Spice
aftershave or WD-40 into the two sections of the pot and see what
happens, you don't have anything to lose, and it has fixed many an old
pot for me over the last 40+ years.

Bob Hofmann

Yuck! why not just swish it around in gasoline, spit in the back and give
it big WHUMP!

Seriously, tuner wash was good stuff but tuners don't have switches anymore
so it's gone! Isopropyl 90% is a cheap and safe wash (70% has too much
water) followed by a drop of very light mineral oil (baby oil). I suspect
there is a lot of Isopropyl in Old Spice. WD-40 leaves a crusty residue as
a corrosion inhibitor. Around here a spray can of Isopropyl costs $15 a can
at the electronic emporium vs. $2 a bottle at the drug store. I can make
the can last 5-10 years.