What was found
SEA FLIGHT NR 2290 WITH NAV AND HSI SELECT ON CAPTAINS SIDE, THE ADVISORY DISPLAY SHOWS DAOC DATA INVALID MESSAGE. CAPTAINS AIRSPEED INDICATOR DROPPED TO ZERO FOR ABOUT 8 - 10 SECONDS. CHECKLIST PROCEDURE WAS FOLLOWED WHICH ADVISED TO CHANGE HSI SELECT TO FIRST OFFICERS SIDE. CAPTAINS AIRSPEED THEN RETURNED TO NORMAL. MAINTENANCE REPLACED NR 1 AIR DATA COMPUTER IAW -8200 MTX TASK CARD 9340014. PERFORMED PITOT/STATIC LEAK TEST IAW MTC 9341101, NO LEAKS NOTED. PERFORMED THE TRANSPONDER TEST IAW MTC 9345001. OPERATIONAL CHECK GOOD. AIRCRAFT RETURNED TO SERVICE.