As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CREW REPORTED AFTER TAKE OFF, RETURNED TO DEPARTURE. THE LEFT AND RIGHT UTILITY BUSSES DEPOWERED, AND WERE UNABLE TO RESET. FOUND REPLACE BPCU MESSAGE ON BPCU, REPLACED PER MM. RAN BOTH ENG PER JRH 2-5-5 AND BOTH UTILITY BUSSES RESET NORMAL.