As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING POST MAINTENANCE CHECK FLIGHT, CREW TESTED THE AIR DRIVEN GENERATOR SYSTEM (ADG). DURING THE TEST THE ADG FAILED LEAVING THE CREW IN COMPLETE ELECTRICAL BLACKOUT. ENGINE DRIVEN SYSTEM WAS BROUGHT BACK ON-LINE AND AIRCRAFT LANDED SAFELY. MAINTENANCE FOUND ADG FAILED INTERNALLY. THE ADG WAS REPLACED.