"Pot" is short for potentiometer. It's an electrical device that converts a mechanical input to an electrical output. In this case, the position of the stick is converted to a variable resistance. They are metal cans about an inch in diameter and half an inch deep, with a shaft protruding from one side, and two or three electric terminals with wires connected. Just near the terminals, there is (usually) an opening that allows access to the inside. To clean them, a spray cleaner/lubricant is sprayed in the opening, while the shaft is rotated back and forth. There are special cleaners used in the electronics industry, but people often use WD-40.
Getting inside the stick to find the pots is left as an exercise for the student.

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