What was found
(CAN) UPON COMPLETION OF ENG START & TURNING ON AVIONICS IN PREPARATION FOR DEPARTURE ON A CHARTER TRIP, CREW OBSERVED SMOKE COMING FROM THE RT AVIONICS. CREW SHUTDOWN ENGINES & MASTER SWITCH & DEPLANED ALONG WITH PAX. MX RESPONDED & AFTER LOCATING SOURCE OF SMOKE & ATTENDED FUMES, REPLACED NAV CONTROL HEAD SET WITH A SERVICEABLE SET & CHARTERED DISPATCHED. NAV CONTROL HEAD - FACE PLATE LIGHT BULB BURNED OUT. REPAIRED & PROVIDED A MAINTENANCE RELEASE (DATED 24 SEPT 04). MATCHING UNIT (OTHER 1/2 OF SET)WAS INSPECTED & TESTED & PROVIDED A MAINTENANCE RELEASE.