As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLIGHT 4172 WAS BOARDED AND MAINTENANCE NEEDED TO REPLACE THE VERTICAL SPEED BUTTON ON THE FLIGHT DIRECTOR PANEL. A SHORT OCCURRED AND THE COCKPIT FILLED WITH SMOKE. THE PASSENGERS WERE DEPLANED AND FLIGHT 4172 WAS CANCELED. MAINTENANCE INSPECTED AND REPLACED THE FLIGHT DIRECTOR PANEL IN ACCORDANCE WITH DORNIER MAINTENANCE MANUAL 22-00-00. OPERATIONAL TESTED WERE COMPLETED AND THE AIRCRAFT WAS RELEASED FOR SERVICE.