What was found
ON TAKEOFF, GEAR HANDLE SELECTED UP-SLIGHT PAUSE ON MOTION WHILE HANDLE RETRACTING GEAR PANEL INSTANTLY SHOWED ONLY 3 RED LIGHTS. AFTER 5-10 SECONDS MAIN DOORS OPENED AND MAINS RETRACTED NOSE DOOR RED NOSE UNSAFE REMAINED ILLUMINATED. EVENT MARKER PUSHED, ALT EXTENSION PERFORMED. RETURNED TO FIELD, LANDING UNEVENTFUL. FERRY FOR REPAIRS. REPLACED SOLENOID SEQUENCE VALVE, MECHANICAL SEQUENCE VALVE AND LANDING GEAR HANDLE ASSY. OPS TEST IAW AMM TASK 32-31-00-710-801 SATISFACTORY. PERFORMED SEVERAL GEAR SWINGS, ALL SATISFACTORY. RETURNED TO SERVICE.