What was found
ORD - FLT 1648 - ON TAKEOFF ORD, FLAPS WOULD NOT RETRACT, STAYED AT 8 DEGREES. RETURNED TO ORD, LANDED WITHOUT INCIDENT, FLAPS RETRACTED NORMALLY. REPLACED FLAP CONTROL UNIT. CYCLED FLAPS SEVERAL TIMES WITH NO FAULTS NOTED. SYSTEM GROUND CHECKED NORMAL OPERATION. (M)