As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED: FLIGHT AIR RETURNED TO ORD ON ACCOUNT OF FIRST OFFICER INSTRUMENTS MALFUNCTIONING. EMERGENCY WAS DECLARED. PILOT REPORTS 1:45 MINUTES INTO CRUISE FLIGHT MAIN DC FEED RPDU #74 CB TRIPPED . NUMEROUS STATUS MESSAGES. MAINTENANCE REPLACED DC 2 CARD M2461807 IAW AMM 24-09-09. TESTS NORMAL.