As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PIT FLT 0540 - EN ROUTE TO MKE, RIGHT GENERATOR FAULTED. APU WAS STARTED AND APU GENERATOR WAS PUT ON LINE. TEN MINUTES LATER, THE APU SHUT DOWN. FLIGHT RETURNED TO PIT DUE TO ONE GENERATOR OPERATION. FLIGHT LANDED WITHOUT FURTHER INCIDENT. MAINTENANCE REPLACED THE GENERATOR CONTROL UNIT AND THE NR 1 GENERATOR. REF: OPERATOR CONTROL NR USAAF98044.