As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
NR 2 GENERATOR WENT OFF LINE EN ROUTE TO PHL FROM ATL. VOLTS AND FREQUENCY CHECKED NORMAL; GENERATOR WOULD NOT RESET. TAIL COMPARTMENT HI LIGHT ILLUMINATED AFTER APU STARTED AS BACK UP FOR ELECTRICAL POWER. AS PRECAUTIONARY MEASURE, FLIGHT CREW ELECTED TO RETURN TO ATL MAINTENANCE BASE. REPLACED NR 2 GENERATOR, AC CONTROL PANEL AND REPOSITIONED TEMP SENSOR.