What was found
DURING CRUISE AT FL280, RED CABIN ALTITUDE WARNING LIGHT ILLUMINATED. PERFORMED AN EMERGENCY DESCENT TO 10,000 FEET AND CONTINUED TO SCHEDULED DESTINATION. CABIN PRESSURE CLIMBED TO 12,000 FEET BEFORE CREW COULD MANUALLY STABILIZE. NO OTHER FAULT LIGHTS AND PASSENGER MASKS WERE NOT DEPLOYED. MAINTENANCE VERIFIED THAT THE LT AND RT PACKS OPERATE NORMALLY AND THAT THE OUTFLOW VALVE MANUALLY OPERATED NORMALLY. REPLACED CABIN PRESSURE POWER TRANSFER RELAY R2-258. OPS CHECKED NORMAL.