As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING CRUISE FLIGHT THE LT ENGINE N1(FAN) INDICATOR WENT TO ZERO, ALL OTHER ENGINE INDICATIONS WERE NORMAL. INVESTIGATION REVEALED THAT THE N1 TACH GENERATOR DRIVE SHAFT HAD SHEARED. REPLACED WITH OVERHAULED UNIT AND OPERATIONALLY CHECKED OK. CAUSE WAS EVIDENTLY METAL FATIGUE, GIVE THE TIME ON THE UNIT SINCE NEW.