As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIR TURNBACK, FLT 7202 SEA TO JUN. UPON ROTATION AND DURING INITIAL CLIMBOUT THE AIRCRAFT APPEARED TO SHED AND REGAIN MULTIPLE DC BUSSES. LOUD RELAY ACTION COULD BE HEARD FROM THE ELECTRICAL PANEL. THIS LASTED FOR 30 TO 45 SECONDS THEN ALL SYSTEMS RETURNED TO NORMAL. REMOVED AND REPLACED THE DC BUSS POWER CONTROL UNIT (BPCU). (S)