What was found
PERFORMED AN AIR TURNBACK. DURING INITIAL CLIMBOUT AFT F/A NOTIFIED FLIGHT DECK THAT THERE WAS A BURNING ODOR AND WHITE VISIBLE SMOKE IN THE AFT CABIN. ODOR DISSIPATED AFTER GALLEY POWER AND CABIN LIGHTS TURNED OFF. MX TROUBLESHOT IAW FIM R & R RECIRCULATION FAN IAW AMM. OPS CHECKS NORMAL. FOUND T1-91 READING LIGHT TRANSFORMER, LOCATED AT AFT CABIN TRANSFORMER PANEL MAKING VIBRATING SOUNDS AND SMELLS BURNED. REPLACED TRANSFORMER T1-91. REPLACED BOTH COALESCER BAGS. PERFORMED DUCT BURNOUT.