What was found
BURNING PLASTIC ODOR IN CABIN. BECAME STRONGER IN THE BACK OF THE AIRCRAFT. SMOKE ALARM DID NOT SOUND, NO ELECTRICAL SYSTEMS, LIGHTS, ALARMS APPEARED TO BE ERRATIC. SHUT DOWN ENTIRE AIRCRAFT PENDING MX CHECK. R & R BOTH LIGHT BALLASTS AT ROW 13A/C IAW AMM 13-095, OPS CHECKED GOOD, NO ODOR.