What was found
LAX - FL6, AFTER TAKEOFF, CREW RECEIVED THE EICAS MESSAGES 'GEAR DOORS' AND THE AMBER DOORS LIGHT WAS ILLUMINATED WITH THE GREEN DOWN LIGHTS EXTINGUISHED. FLIGHT RETURNED TO LAX AND LANDED WITHOUT NO FURTHER INCIDENT. MAINTENANCE FOUND THE CRANK ARM ASSEMBLY ON THE NOSE GEAR SEQUENCE VALVE BROKEN AND REPLACED IT. (M)