What was found
LOSS OF CABIN PRESSURIZATION OCCURRED AT 17,000 FEET. CABIN ALTITUDE REACHED 11,000 FEET AND AN EMERGENCY DESCENT WAS MADE TO 10,000 FEET. CABIN PRESSURE WAS REGAINED. FLIGHT WAS RETURNED TO DTW AND LANDED WITHOUT INCIDENT. MAINTENANCE REPAIRED HOLE IN AIR CONDITIONING DUCT BY AIR CYCLE MACHINE. ALSO, REPLACED CABIN PRESSURE CONTROLLER AND AMPLIFIER. OPERATIONAL CHECK NORMAL.