As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
LAS - SMOKE FUMES - FLT 729 - S - EN ROUTE FROM LAS TO ORD DURING TOP OF DESCENT FLIGHT CREW NOTICED AN UNUSUAL VIBRATION AND THEN A SLIGHT SMELL OF ELECTRICAL SMOKE, THE BLOWER AND EXTRACT FANS WERE TURNED OFF AND THE NOISE AND SMELL WENT AWAY. MAINTENANCE REMOVED AND REPLACED THE AVIONICS COOLING FAN IAW AMM 21-26-51. VENDOR REPAIR STATION CONFIRMED FAILURE OF AVIONICS FAN S/N 4156, ENTRY TEST OF UNIT FOUND THE FAN SEIZED AND FURTHER TEARDOWN IDENTIFIED THE FRONT BEARINGS AS DISINTEGRATED.