As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED: STANDBY DC FEED RPDU71 ELECTRICAL CIRCUIT BREAKER TRIPPED RESULTING IN SEVERAL MESSAGES. AN EMERGENCY WAS DECLARED AND THE AIRCRAFT RETURNED TO DFW WHERE IT LANDED SAFELY WITHOUT FURTHER INCIDENT. MAINTENANCE FOUND P300M2 SLOT 5 DC4 CARD FAULTING. REPLACED CARD AND ACCOMPLISHED A SATISFACTORY OPERATIONAL CHECK PER AMM 24-09-09-00A-720A-A.