In this amp repair video, I'm showing how to clean the pots. Just a little spray into each (small opening in the pot casing) and then work the knob.
I WOULD RECOMMEND TURNING OFF THE AMP AND UNPLUGGING FROM THE WALL FIRST.
Clean the jacks also and make sure they are nice and tight to the feel. By that I mean plug in and out the guitar chord to make sure there is a tight grip. If not, I recommend changing the plug which will require solder/unsolder chops on these units. Notice the soldering video, I will cover unsoldering in another video.