What was found
RETURNED TO COS WITH SMOKE IN AFT CABIN. PACK OPERATION CHECKS NORMAL. NOTED THAT LIGHTS IN SIDE PANEL AT 19 AND 20 WERE INOPERATIVE AND OVERHEAD LIGHTS AT 15, 16, 17 ABC, 3 AND 4 AB WERE INOPERATIVE. SUPPLEMENTAL DATA UPDATE: POSSIBLY OVERHEATED BALLAST. REPLACED BALLAST AND REPAIRED LIGHTS AT SEATS 15, 16, 17 ABC AND 3 AND 4 AB.