What was found
AIRCRAFT ENROUTE, DESCENDING FROM FL450 THROUGH FL280 WITH ENGINES AT FLIGHT IDLE. CABIN PRESSURE ROSE TO 15,000 FT WITH ASSOCIATED CABIN PRESSURE WARNING ANNUNCIATOR LIGHT, PAX O2 MASKS AUTOMATICALLY DEPLOYED. EMERGENCY DECLARED AND CREW INITIATED A RAPID DESCENT. FLIGHT CONTINUED ON TO DESTINATION AT A SAFE LOWER ALTITUDE. CABIN PRESSURE CONTROLLER WAS MEL'D UNDER 21-12 AND ACFT REPOSITIONED UNPRESSURIZED TO SERVICE CENTER FOR REPAIRS. CABIN PRESSURIZATION CONTROLLER WAS REPLACED AND A NON-REVENUE FUNCTIONAL CHECK FLIGHT WAS ACCOMPLISHED WITH NO PRESSURIZATION FAULTS FOUND.