What was found
BUR - DURING DESCENT BOTH PACKS SHUTDOWN. PRIOR TO LEFT PACK RETURNING THE PASSENGER OXYGEN MASKS DEPLOYED. LANDED BUR WITHOUT INCIDENT. AIRCRAFT TAKEN OUT OF SERVICE FOR EVALUATION. REPLACED BOTH AIRCONDITIONING WATER SEPARATOR ASSEMBLIES. REPLACED LEFT AND RIGHT PACK ANTI-ICE VALVES. REPLACED RIGHT PACK PRESSURE REGULATOR OVER-RIDE VALVE S2-40. REPLACED BOTH CABIN DIFFERENTIAL PRESSURE SWITCHES S1-485 & 486 AND REPAIRED CHAFFED WIRE AT SINGLE ENGINE SECOND SEGMENT CLIMB PRESSURE SWITCH. SYSTEM GROUND CHECKED NORMAL OPERATION.