What was found
LAS - FLT 2606 - WHILE AT CRUISE AT 35,000 FT, 72M W/AUTOPILOT ENGAGED, THE A/C EXPERIENCED A SHARP LEFT YAW. DISENGAGED THE AUTOPILOT. A/C DIVERTED TO LAS. INSPECTED A/C, FOUND TO BE SAFE FOR MX. FERRY TO PHX. R/R'D THE YAW DAMPER COUPLER, AUTOPILOT ACCESSORY UNIT, AND THE P5-3 CONTROL MODULE. THE P5-3 WAS CHANGED FOR THE EARLIER FINDINGS OF UNCOMMANDED RUDDER INPUT, THAT BEING WHEN THE B-CHANNEL FLT CONTROL SW GUARD WAS RESET IT TRIPPED THE AUTOPILOT AND YAW DAMPER OFF. REPLACED RUDDER PWR CONTROL UNIT (PCU), PERFORMED ADJ TEST W/NO PROBLEMS. YAW TEST DAMPER TEST PERFORMED. THE PCU HAS BEEN PLACED UNDER QUAR FOR INVESTIGATION BY THE NTSB. (M)