As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ENGINE GEAR DRIVEN ALTERNATOR FAILED AFTER 14 HOURS TIME-IN SERVICE. ROTOR SHAFT BROKE AT STOP COLLAR GROVE. NO PHYSICAL DAMAGE FOUND INSIDE ALTERNATOR AND BEARINGS TURN FREELY. SUSPECT MATERIAL FLAW OR IMPROPPER MATERIAL IN ROTOR SHAFT, COMBINED WITH SHARP EDGES OF MACHINED GROOVE, RESULTED IN SHAFT BREAKING. SUGGEST CHOSEN MATERIAL OF ROTOR SHAFT BE REVIEWED FOR SUITABILITY AND/OR CONFORMANCE TO SPECIFICATION.