As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING MAINTENANCE INSPECTION FOUND THE NR 4 EMERGENCY POWER SUPPLY UNIT NEEDS TO BE REPLACED. THE AIRCRAFT WAS REMOVED FROM SERVICE. REMOVED AND REPLACED THE NR 4 BATTERY ASSY ON NR 4 EPSU IAW W/C 33-700-19. THE OPERATIONAL CHECK WAS GOOD. THE AIRCRAFT WAS RETURNED TO SERVICE.