Tonight I dug out my electric guitar for the first time in a couple of years and the tone & volume controls and pickup switch are so dirty they keep cutting the signal out. Can anyone recommend a way to clean these up? (other than taking it to a repair shop) I've got a can of circuit board cleaner (ie an aerosol of CFCs from back in the day before they were banned) would this be any good or do more damage? The guitar in question is a Samick Les Paul copy. Any advice gratefully appreciated.