As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
IN CRUISE FLIGHT, NR 1 SERVO CAUTION LIGHT CAME ON. CHECKED HYD SCHEMATIC PAGE WHICH SHOWED ALL NT 1 SYS SERVOS IN YELLOW, REFERENCED EMERGENCY PROCEDURES CHECKLIST FOR NR 1 SERVO CAUTION LIGHT. LOWERED LANDING GEAR AND RETURNED TO DEPARTURE. DEFECTIVE SWITCH. REPLACED SWITCH.