Mine had loud static when it was turned. Had no luck ad disassembling radio and the switch was probably not servicable. Figured I would replace the part but tried to spray DOxit (Caig Labs) in the side of the knob. Static stopped and has been fine for months since.
Tuner cleaned should work about the same.
I would just have the radio off when spraying.

Can't hurt, Might help.

Tony
'91 100Q 5spd