What was found
UNIT LOCK UP, WILL NOT TRANSFER MODE 'A' CODES FROM STANDBY TO ACTIVE WINDOW. THIRD UNIT IN AIRCRAFT SINCE ORIGINAL PURCHASE IN APRIL, 1995. FIRST UNIT FAILED COMPLETELY OUT OF BOX. SECOND UNIT WORKED FOR 6 HOURS, THEN WOULD NOT REPLY. THIS UNIT WORKED FOR FIRST THREE FLIGHTS, THEN FAILED INTERMITTENTLY.