What was found
DURING CLIMB-OUT OF KTOL WITH RUDDER POWER ON, YAW DAMPER ON AND AUTO PILOT ON THE RUDDER HAD A LEFT RUDDER INPUT. THE CREW TURNED THE AUTO PILOT OFF AND THE CONDITION REMAINED, TURNED THE YAW DAMPER OFF AND NO CHANGE. THE LEFT INPUT WENT AWAY ONLY WHEN RUDDER POWER WAS TURNED OFF. THE CREW RETURNED TO KTOL AND LANDED WITHOUT INCIDENT. MAINTENANCE TROUBLESHOT THE SYSTEM AND FOUND A DEFECTIVE YAW CHANNEL COMPUTER. THE YAW CHANNEL COMPUTER WAS DEFERRED AND THE ACFT WAS RETURNED TO SERVICE.