What was found
ON DESCENT INTO KORD CREW SMELLED SMOKE IN THE COCKPIT AND EQUIPMENT COOLING "SMOKE" LIGHT CAME ON FIVE MINUTES AFTER SMOKE ODOR STARTED. EQUIPMENT COOLING SYSTEM PREVIOUSLY ENTERED ON DMI PER MEL 21-33. CREW CONTINUED DESCENT AND LANDED SAFELY. UPON INVESTIGATION AND TROUBLESHOOTING FOUND COOLING VENTS ON TRANSFORMER RECTIFIER UNITS NR 1, NR 2, AND NR 3 OBSTRUCTED. CLEANED VENTS IAW AMM 20-60-06, AND PERFORMED EQUIPMENT COOLING SYSTEM TEST IAW AMM 21-58-00, ALL OPERATION NORMAL. PERFORMED SMOKE OR FUMES IN CABIN CONDITIONAL INSPECTION IAW AMM 05-51-50, NO FAULT NOTED. AIRCRAFT RESTORED TO NORMAL.