As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER DEPARTING MKE THE LEFT GENERATOR DROPPED OFF LINE AND RESET WITHOUT ANY ACTION FROM CREW. AIRCRAFT RETURNED TO MKE. LANDING WAS UNEVENTFUL. INSPECTION OF LEFT STARTER/GENERATOR FOUND THE THREADS ON THE STARTER/GENERATOR GROUND TERMINAL ADAPTER HAD FAILED ALLOWING THE GROUND LEAD TO LOOSEN. GROUND TERMINAL ADAPTER WAS REPLACED WITH NEW. OPERATIONS CHECKS GOOD.