What was found
(CAN) AFTER STARTUP & RUNNING ON FLIGHT IDLE THE HELICOPTER CREW EXPERIENCED A SHAKING & ROCKING IN THE AIRFRAME. CREW SHUTDOWN HELICOPTER WITHOUT INCIDENT & INSPECTED THE HELICOPTER. NO FAULTS WERE FOUND VISUALLY. HELICOPTER STARTED & SHAKING BEGAN ONCE AGAIN. THE PILOT & AME WERE ABLE TO ELIMINATE THE SHAKING BY PULLING THE YAW CSAS CB. YAW CSAS SYS WAS DISABLED & DEFERRED FOR FLIGHT BACK TO MX HANGAR UNDER VFR CONDITIONS. YAW CSAS SYS INSPECTED & FOUND A BROKEN WIRE IN THE COMPUTER PLUG THAT WHEN IN OPEN CIRCUIT CONDITION CAUSED THE COMPUTER TO PUT OUT TOO HIGH OF A VOLTAGE TO THE COMPONENTS. WIRE WAS REPAIRED & SYS WAS TESTED SERVICEABLE, INCLUDING A SATISFACTORY TEST FLIGHT. FAULT CLOSED & ACFT RETURNED TO SERVICE.