What was found
SMOKE IN CABIN, RETURN TO AUG, PBE AND HALON FIRE EXTINGUISHER USED. THIS AIRCRAFT WAS THEN INSPECTED BY MAINTENANCE PERSONAL, A BALLAST WAS REMOVED AT ROW 9F, CONNECTORS STOWED, AND WINDOW LIGHTS CB F24 WAS PULLED AND COLLARED, AND FERRIED TO ALB FOR REPAIRS. ALB MAINTENANCE REPLACED BALLAST AT ROW 9F AND FOUND CONNECTOR 426VP-P1 SHORTED AND MELTED. REPLACED PLUG; ALSO FOUND CONNECTOR 426VP-J1 SHORTED AT PINS 23 AND 24, REQUIRING REPLACEMENT. BALLAST WAS CONSIDERED BY MECHANIC TO BE THE ROOT CAUSE.