As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) RED (ESSENTIAL POWER ONLY) POSTED CRUISE FLIGHT AT FL370 WITH TRIPLE CHIME FOR ABOUT 1 SECOND AND CLEARED. NO LOSS OF ELECTRICAL POWER REPORTED BY THE CREW. MAINTENANCE COULD NOT DUPLICATE AND RERACKED PCB-3. OPS CHECK GOOD. AC RTS`D (TC# 20190422016)