As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
SEA FLIGHT NR 2210 BOTH ANTI COLLISION LIGHTS (WHITE) ON WINGS FLASHING APPROXIMATELY 250 TO 300 TIMES PER MINUTE. MAINTENANCE GROUND RAN AIRCRAFT. DUPLICATED DISCREPANCY ISOLATED TO RIGHT HAND ANTI COLLISION POWER SUPPLY. REPLACED RIGHT HAND POWER SUPPLY IAW Q200 AMM 33-40-81-000-805 AND 32-40-27-710-801. GROUND RAN AIRCRAFT AGAIN NO OTHER DEFECTS NOTED. ALL OPERATIONAL CHECKS GOOD. AIRCRAFT RETURNED TO SERVICE.