What was found
PILOT REPORTED STRONG ODOR (BURNING PLASTIC) COMING FROM OVERHEAD SEAT 5A, 6A IN FLIGHT. CREW DECLARED EMERGENCY INBOUND TO PIT. FIRE DEPARTMENT DISPATCHED, NO FIRE REPORTED. PSA MAINTENANCE FOUND A BURNED BALLAST UNIT CAUSING ODOR. MAINTENANCE DEACTIVATED UNIT, RAN ENGINES FOR 30 MINUTES, NO ODOR PRESENT. AIRCRAFT WAS RELEASED FROM MX WITH MEL ON OVERHEAD LIGHTING. (M)