What was found
AFTER TAKEOFF FROM LMT, PILOT NOTICED SMOKE COMING FROM AVIONICS VENT ON GLARE SHIELD. ELECTRICAL ODOR ACCOMPANIED SMOKE. OXYGEN MASK WAS NOT USED. AIRCRAFT RETURNED TO FIELD WITHOUT INCIDENT. MAINTENANCE VISUALLY INSPECTED WIRING BEHIND INSTRUMENT PANEL, CIRCUIT BREAKERS AND RAN ELECTRICAL SYSTEMS. COULD NOT DUPLICATE. A/C WAS RETURNED TO SERVICE. FURTHER INVESTIGATION IN PDX REVEALED SHORTED WIRE IN RADAR ALTIMETER WIRE BUNDLE. WIRE HAS BEEN REPAIRED AND A/C RETURNED TO SERVICE.