What was found
DURING CLIMBOUT, THE DUCT-AVIONIC COMPARTMENT OVERHEAT LIGHT ILLUMINATED. CABIN ALTITUDE COULD NOT BE REGULATED AND CONTINUED CLIMBING A 750 FPM. RETURNED AIRCRAFT TOMSP. ON TAXI IN SMOKE REPORED IN THE AFT CABIN. FOUND THE NR 1 AIR CYCLE MACHINE TO BE WEAK AND TEMPERATURE CONTROL VALVE INDICATION TOB EE INOPERATIVE. REMOVED AND REPLACED BOTH TEMPERATURE CONTROL VALVE AND NR 1 AIR CYCLE MACHINE. OPERATIONALLY CHECKS GOOD.