21-03-2011, 02:15 PM
They can be dismantled carefully.. and the little inserts within replaced.. I once had to do 32 of them on the backside of an HH mixing desk. Chances are they have lost their "spring" over the years and rather than being dirty are either actually physically broken or the plating worn away. A decent supplies shop should stock similar switches so you may be able to mix and match bits to get something working... The fallback total bodge is to use some of the thick copper "foil" for 20's style baseboard screening and make new inserts. You can harden it up somewhat by burnishing it between steel edges.
