As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
SHORTLY AFTER TAKEOFF, THE PILOT REPORTED THAT THEIR HSI WAS INOPERATIVE WHICH WAS ACCOMPANIED BY A SMOKE ODOR IN THE COCKPIT AND ELECTED TO RETURN FOR A LANDING. UPON INSPECTION AND CONFIRMATION BY MX, THE HSI WAS SUBSEQUENTLY REPLACED AND THE ACFT WAS RELEASED FOR SERVICE.