What was found
HAD ZNS ON NR 3 GENERATOR, RESET FIELD AS PER QRH. 5 MINUTES LATER GENERATOR TRIPPED AGAIN. RETURNED TO OAK AS PER OPS. RESET NR 3 BUS FAULT, RESET FAULT SW FOR LANDING. MAINTENANCE TRANSFERED TO DMI IAW MEL 24-1 CONTROL NUMBER 703260, CAT C NR 3 GENERATOR DISCONNECTED, PLACARD INSTALLED.