As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
BACKUP ELECTRICAL SYSTEM EICAS MESSAGE DISPLAYED, INDICATING FAILURE OF BACKUP ELECTRICAL SYSTEM. BACKUP CONVERTER AND LEFTHAND BACKUP GENERATOR WERE REPLACED. VENDOR CONFIRMED FAILURE OF THE PMG STATOR WINDINGS IN THE BACKUP GENERATOR. ALSO, THE BACKUP CONVERTER WAS FOUND TO BE DEFECTIVE.