Just to add to Bill's advice
, you can use DeoxIT sparingly, you only need to wet the contacts, not drown them. That way, a can goes a long way.
If DeoxIT doesn't help, then the contacts weren't dirty to begin with; it really does a good job at cleaning
All men dream: but not equally. Those who dream by night in the dusty recesses of their minds wake in the day to find it was vanity: but the dreamers of the day are dangereous men, for they may act their dreams with open eyes, to make it possible. T.E. Lawrence