What was found
500 HRS INTO FLT AT CRUISE FL 360. CREW HEARD AN ARCING SOUND BY THE RT OBSERVERS POSITION, LIGHT SMOKE AND AN ACRID SMELL WERE ALSO NOTED. THE OVER-HEAD SWITCH PANEL LTG (C-30) CIRCUIT BREAKER POPPED AND SMOKE AND FUMES DISAPATED. OVERHEAD PANEL LIGHTS WERE OUT THE REMAINDER OF FLIGHT. NO OTHER MALFUNCTIONS ON AC BUS 3 NOTED. T/S IAW FIM 33-11, FOUND OVERHEAD LAMP DIMMER (U1-13 0) R & R O/H LAMP DIMMER IAW MM 33-11-03-2. ACFT OK FOR SERVICE, CLEARS PIREP. PREMATURE REMOVAL/INSTALLATION.