Disassembly and Cleaning with Isopropyl Alcohol (99%) may repair part.
Replacement may be tricky, for a new part.
As I remember, Turner did not use a 1/4 inch potentiometer.
Rather they used a 3/16 inch or 1/8 inch control. The 3/16 inch is rare these days,
since the electronics industry has standardized on 1/4" and 1/8" versions.