Johnson JT50. Cleaning pots and controls.

[1blueheron]

Before we started on the tube amps, my son bought a used Johnson JT50 "mirage" SS amp with the pedal controller.  It's not a bad sounding amp but it has some erratic issues with the master volume and gain pots as well as the selector switches.  Some times there is scratching/poping but most of the time it is a muting type effect, especially with higher frequencies. I am guessing they are just dirty and need cleaned.  Any of you ever been inside the belly of one of these beasts?  Wondering if they are sealed or if I can access them.  If I can access them, what would y'all recommend for cleaning them?  Ive got a can of old TV tuner cleaner  I thought might be worth a try before I go and buy new pots/switches.