As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) SHORTLY AFTER TAKEOFF, THE CREW REPORTED A SMELL OF BURNING ELECTRICAL INSULATION, WITH A STRONGER SMELL IN CABIN. AIRCRAFT RETURNED TO BASE. INVESTIGATION FOUND THAT THE FLUORESCENT LIGHT SOCKET IN THE CARGO AREA HAD COME APART CAUSING IT TO SHORT OUT.