As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
HSI HAD FAILED DURING CRUISE FLIGHT ON AN IFR FLIGHT PLAN. SMOKE EMITTED FROM THE INSTRUMENT WITH THE BREAKER TRIPPING. SMOKE WAS BOTH VISIBLE & WAS ABLE TO BE SMELLED. QRH WAS IN HAND IN CASE SMOKE WAS NOT SUBSIDING & AN EMER LANDING AIRPORT WAS FOUND BUT NOT NEEDED. ATC WAS INFORMED OF SITUATION NO EMER WAS DECLARED DUE TO SMOKE SUBSIDING. R & R HSI.