As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
SHORTLY AFTER TAKEOFF, THE RT ENGINE STARTED LOSING OIL PRESSURE. THE PILOT RETURNED TO THE DEPARTING AIRPORT. INSPECTION OF THE OIL FILTER REVEALED A LARGE QUANTITY OF METAL. ON ENGINE TEAR DOWN, THE ALTERNATOR DRIVE GEAR WAS FOUND BROKEN. THE ALTERNATOR FRONT BEARING WAS DESTROYED. SUBMITTER SUGGESTED 500-HOUR SERVICE LIFE ON BEARING, 250-HOUR INSPECTIONS.