What was found
(CAN) PILOT REPORTED HEARING A NOISE AND THEN NOTICED HIS ALTERNATOR WAS OFF LINE. AIRCRAFT LANDED WITHOUT FURTHER INCIDENT. MAINTENANCE FOUND THAT THE HOUSING HALVES ON THE ALTERNATOR WERE QUITE LOOSE. REPLACE ALTERNATOR STILL NO CHARGE. FURTHER REPLACED VOLTAGE REGULATOR AND TEST RUN. FOUND CHARGING SYSTEM OPERATIONAL. THE ALTERNATOR HAS REGULAR 500 HOUR BRUSH INSPECTIONS. THE LAST BRUSH INSPECTION WAS 470 HOUR PRIOR TO THIS OCCURRENCE. TSOH 1393.1.