As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING CLIMB, THE NR 1 ENGINE OPERATING PARAMETERS BECAME ERRATIC. AIRCRAFT RETURNED TO SFO AND LANDED WITHOUT FURTHER EVENT. GROUND MAINTENANCE FOUND THE PERMANENT MAGNET ALTERNATOR HAD FAILED DUE TO A LOOSE PMA ROTOR SHAFT IN THE GEAR BOX. MAIN GEAR BOX AND PMA WERE REPLACED. AIRCRAFT WAS GROUND RUN AND FOUND SERVICEABLE.