As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PIT/STL - FLT 1531 - EN ROUTE TO STL APPROXIMATELY 90NM EAST OF IND, ESSENTIAL AC POWER BUS FAILED. FLIGHT DIVERTED TO IND FOR MAINTENANCE PURPOSES. NO EMERGENCY WAS DECLARED. FLIGHT LANDED IND WITHOUT INCIDENT. MAINTENANCE REPLACED GROUND POWER CONTROL UNIT. SYSTEM CHECKED NORMAL. (X)