As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING FLIGHT, TRIPLE TACH FAILED WHEN REDUCING TWIST GRIP FROM FLIGHT TO IDLE. A TEST FLIGHT EVAL REVEALED ROTOR INDICATION GOES TO ZERO BOTH ANALOG AND DIGITAL. ROTOR RPM SPEED PICK-UP FAILED INSPECTION IAW AMM 62-41-00, 4-1 PROCEDURE E1. REMOVED AND REPLACED SPEED PICK-UP IAW AMM 62-41-00, 4-1.