What was found
IAD FLT1724, ON DESCENT, CREW REPORTED THERE WAS NO INDICATION OF GEAR EXTENSION (RED OR GREEN LIGHTS) WHEN LANDING GEAR HANDLE WAS PUT IN THE DOWN POSITION. CREW PERFORMED QUICK REFERENCE HANDBOOK PROCEDURES AND EXTENDED THE GEAR MANUALLY. STILL NO LIGHTS. FLIGHT DIVERTED TO IAD FOR LONGER RUNWAYS. AIRCRAFT LANDED AND TAXIED TO THE GATE WITHOUT FURTHER INCIDENT. AN EMERGENCY WAS DECLARED. MAINTENANCE INSPECTED GEAR INDICATION LIGHTS AND FOUND THEM INOPERATIVE DUE TO MASTER DIM BEING PARTIALLY INOPERATIVE. REMOVED AND REPLACED ANNUNCIATOR AND DIMMING MODULE M469. ALSO, REMOVED AND REPLACED RELAYS R33, R34, R87, DIODE M208, AND CARDS M560 AND M564 IAW MM 33-13-11, 33-18-18 AND 33-18-17. OPERATIONAL CHECK OF MA