Here is a tip for your hi-fi gear: get a can of De-Oxit D5. The common mode of failure for those 'knobs' is the potentiometers getting gunk and oxidization on t

Here is a tip for your hi-fi gear: get a can of De-Oxit D5. The common mode of failure for those 'knobs' is the potentiometers getting gunk and oxidization on their carbon traces. They work by sliding fingers over a carbon trace which increases making resistance change as it moves on the circle (or line, for slide pots). Also, since they rely on physical contact between two surfaces, it helps tremendously to have a non-interfering lubrication between them. De-Oxit D5 has a contact cleaner in aerosol which flushes gunk out and it leaves behind a compound which prevents corrosion and lubricates electronic contacts. It is in the bag of every tech who works regularly with hi-fi gear. Note this applies to analog controls. Digital controls use rotary encoders which only indicate which direction the dial has been moved.