What was found
(CAN) DURING CLIMB, FLIGHT/CABIN CREWS NOTICED A BURNING PLASTIC SMELL THROUGHOUT THE CABIN AND COCKPIT. DECISION WAS TAKEN TO RETURN AND LAND. AS THE ACFT TURNED BACK, CABIN CREW DEACTIVATED THE COFFEEMAKERS AND SMELLS DISSIPATED. AN EMERGENCY WAS DECLARED AND THE ACFT LANDED WITHOUT FURTHER INCIDENT. TROUBLESHOOTING REVEALED THAT THE LT OVERHEAD LIGHT PUSH BUTTON ON THE GALLEY CONTROL PANEL HAD OVERHEATED. THE PUSH BUTTON SWITCH WAS REPLACED AND THE ACFT RELEASED IN SERVICE.