CASA 235 EXPERIENCED SMOKE IN THE COCKPIT; ORIGINATING FROM A CIRCUIT BREAKER PANEL. FLT CREW DIVERTED TO NEAREST ARPT FOR UNEVENTFUL LNDG.

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WE WERE OPERATING PART 91 ON AN IFR FLT PLAN AT 17000 FT MSL. IT WAS A CLR NIGHT WITH 10 MI PLUS VISIBILITY. THE CREW CONSISTED OF MYSELF; A FO; AND FLT MECH. THERE WERE NO PAX AND NO CARGO. THE FO RPTED SEEING SPARKS AND SMOKE FROM THE R REAR CIRCUIT BREAKER PANEL LOCATED ON THE BULKHEAD BEHIND HIS HEAD. THE AUTOPLT AND FLT DIRECTOR DISCONNECTED AND MOST OF THE LIGHTING ON THE FO'S SIDE OF THE COCKPIT FAILED. BEING JUST W OF ZZZ; I DIRECTED THE FO TO NOTIFY ZZZ APCH THAT WE NEEDED TO DIVERT THERE FOR LNDG. THE FO RADIOED ZZZ AND NOTIFIED THEM THAT WE HAD SMOKE AND NEEDED TO LAND. APCH CTL GAVE US VECTORS TO FINAL AND WE LANDED AT ZZZ. THE SPARKS AND SMOKE HAD CLRED PRIOR TO LNDG. UPON LNDG; THE TWR ASKED IF WE NEEDED ASSISTANCE; WHICH WE DIDN'T. WE TAXIED TO THE FBO AND SHUT DOWN THE ACFT WITHOUT INCIDENT. THE CIRCUIT PANEL BREAKERS WERE POPPED AND SMOKE RESIDUE COULD BE SMELLED. THE MECH PULLED THE CIRCUIT BREAKER PANEL OUT AND FOUND A WIRE BUNDLE WITH EVIDENCE OF HEAT DAMAGE. AS THE SMOKE WAS MINIMAL I CHOSE NOT TO USE OXYGEN AND DUE TO THE FACT THAT THE FO HAD NOTED SPARKS INITIALLY; I DID NOT WANT TO CHANCE INTRODUCING OXYGEN INTO THE COCKPIT FOR FEAR OF IGNITING A FIRE. WITH THIS IN MIND; I CHOSE TO IMMEDIATELY DIVERT TO THE NEAREST ARPT AND LAND. FIRE EXTINGUISHERS WERE NOT USED AS THE SPARKS AND SMOKE CLRED ALMOST IMMEDIATELY UPON THE CIRCUIT BREAKERS POPPING. APPROVED MODIFICATIONS WERE MADE AT THE ARPT THE ACFT WAS PICKED UP FROM. IF ANY OF THESE MODIFICATIONS INCLUDED WORK ON OR AROUND THE CIRCUIT BREAKER PANEL IN QUESTION; THIS AREA SHOULD BE REVIEWED TO DETERMINE IF THERE IS ANY RELATION TO THE CAUSE OF THE CIRCUIT BREAKER PANEL SITUATION.