What was found
ORD - FLT 523 - EN ROUTE ORD-PSP, SHORTLY AFTER TAKEOFF, NOSE LANDING GEAR DID NOT RETRACT. RETURNED ORD AND LANDED WITHOUT FURTHER INCIDENT. REPLACED NOSE LANDING GEAR SHRADER VALVE. ACCOMPLISHED NOSE LANDING GEAR EXTENSION RETRACTION TEST. NO DEFECTS FOUND. SYSTEM GROUND CHECKED NORMAL OPERATION. (M)