What was found
LAS - EMERGENCY LANDING - FLT 0216 - EN ROUTE PHX TO LAS AT APPROXIMATELY FL 280 NOTICED AN ELECTRICAL BURNING SMELL IN COCKPIT FOLLOWED BY REPORT OF WHITE SMOKE IN CABIN BY FLIGHT ATTENDANT, DECLARED EMERGENCY AND LANDED WITHOUT FURTHER INCIDENT. MAINTENANCE FOUND LT PACK AIR CYCLE MACHINE SEIZED, REMOVED AND REPLACED AIR CYCLE MACHINE IAW AMM 21-52-21, OPERATIONAL CHECK WAS GOOD. UNABLE TO PERFORM PRETEST DUE TO HIGH BREAKAWAY TORQUE, UNIT SEIZED. VENDOR FAILURE ANALYSIS SHOWS THRUST BEARINGS AND SPRING SUPPORT WORN. UNIT WAS OVERHAULED AND TESTED IAW OEM 21-52-02 REV 7.