As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT PERFORMED AN UNSCHEDULED LANDING DUE TO SOURCE OFF, GEN OFF & BUS ON LIGHTS TURNED ON. THE FLIGHT CREW ACCOMPLISHED THE QRH 6.4 PROCEDURE & APU WAS NOT STARTED, CONFIRMING THE FAILURE. PERSONNEL REVISION DETECTING LT IDG FAILED, SO THE LT IDG WAS DEFERRED IAW MEL 24-1 CAT B, THE LT GCU WAS REPLACED IAW AMM 24-21-81. TESTED CORRECT & THE REPORT WAS CLOSED.