What was found
(CAN) SMOKE STARTED TO STREAM FROM THE FMS IN FLIGHT, QRH ACTIONED, OXYGEN DONNED, PAN STATUS AND SQUAWKED 7700 ON THE TRANSPONDER. SIGNIFICANT COMMUNICATION ISSUES AROSE THROUGH THE USE OF OXYGEN MASKS EVEN THOUGH THE CORRECT PROCEDURE OF SWITCHING THE INTERPHONE OFF WHEN EITHER PILOT WAS NOT TALKING WAS USED. FO HANDED THE CAPTAIN THE BCF, HOWEVER THE CAPTAIN WASN`T SURE SPRAYING THE OUTSIDE OF THE FMS WAS GOING TO MAKE ANY DIFFERENCE AS THERE WERE NO VISIBLE FLAMES. FO DISCONNECTED THE AUTOPILOT TWICE, HOWEVER CAPTAIN REINSTATED THE AUTOPILOT AS PILOT FLYING AND SWITCHED TO VOR LOC FROM RNAV AS FMS HAD SHUTOFF. CREW DECIDED TO SEEK NEAREST SUITABLE AIRPORT FOR AN INFLIGHT DIVERSION. BRIEFED THE FLIGHT ATTENDANTS ON SMOKE IN THE COCKPIT, THEY HAD 6 MINUTES TO PREPARE FOR LANDING, MADE A PA TO THE PASSENGERS AND EXPLAINED THERE WAS SMOKE IN THE COCKPIT AND THAT WE WOULD HAVE THEM ON THE GROUND SAFELY IN 10 MINUTES. NORMAL LANDING, TAXIED CLEAR OF THE RUNWAY AND MADE A PRECAUTIONARY DISEMBARKATION. FO DISEMBARKED TO MANAGE THE PASSENGERS CAPTAIN STAYED ON OXYGEN UNTIL EVERYONE WAS OFF THEN SEARCHED AIRCRAFT TO CONFIRM THIS. FMS (UNIVERSAL UNS-1C+) REPLACED WITH SERVICEABLE UNIT IN ACCORDANCE WITH SMITHS AERSPACE ENGINEERING ORDER (E.O) 108274 REVB. DATABASE UPDATE CARRIED OUT IAW UNIVERSAL UNS 1C+ TECHNICAL MANUAL 34-60-22. COFIGURATION CHECKED IAW UNIVERSAL CONFIG MANUAL 34-60-26. OPERATIONAL TEST CARRIED OUT IAW UNS-1C+ MANUAL 34-60-22. NIL DEFECTS EVIDENT. STRIP REPORT RECEIVED FROM UNIVERSAL. TSE FOLLOWING UP WITH OEM RE IDENTIFICATION OF BOARDS WITH ORIGINAL C15 AND C2 CAPACITORS TO UNDERSTAND OUR EXPOSURE TO THE ORIGINAL CAPACITOR DESIGN.