Dead drivers on two On30 Forneys

[RRPETE]

My Forneys both pick up on the rear slider trucks, but neither does on either of the 4 main drivers. Can't see any loose or disconnected wires on the main board in the fuel bunker or the small card on the bottom under the Sound on Board cover. Have cleaned the back sides of the drivers where the contacts ride, and the contacts themselves. They worked a year ago before I moved to another state and started a new layout. Any suggestions?  Thanks.

Pete Birdsong