What was found
(CAN) AFTER DEPARTING, THE CREW OBSERVED A NR 2 GENERATOR FAULT AND THE CREW ELECTED TO RETURN TO POINT OF DEPARTURE. MAINTENANCE REPLACED THE NR 2 GENERATOR CONTROL UNIT (GCU) AN THE AIRCRAFT WAS CHECKED SERVICEABLE AN RETURNED TO SERVICE. THE PROBLEM REOCCURRED APPROXIMATELY ONE HOUR AFTER THE AIRCRAFT HAD MADE A SECOND DEPARTURE. THE AIRCRAFT RETURNED TO POINT OF DEPARTURE WITHOUT FURTHER PROBLEM. MAINTENANCE REPLACED THE NR 2 STARTER GENERATOR AND THE AIRCRAFT RETURNED TO SERVICE WITHOUT FURTHER PROBLEM REPORTED. (TC NR 20070911001)