What was found
SHORTLY AFTER TAKEOFF, ENROUTE, THE F/O ADI FAILED. CREW REPORTED THE CIRCUIT BREAKER WAS TRIPPED AND THAT A SLIGHT ELECTRICAL ODOR WAS PRESENT IN THE COCKPIT. FLIGHT RETURNED TO FIELD AND LANDED WITHOUT FURTHER INCIDENT. NO EMERGENCY WAS DECLARED. MAINTENANCE FOUND THE FO ADI EMMITTING THE ELECTRICAL ODOR. REMOVED AND REPLACED ADI AND INSPECTED WIRING. NO PROBLEMS FOUND WITH WIRING. PERFORMED SATISFACTORY FUNCTIONAL CHECK. A SECOND ADI WAS REPLACED FOR THE SAME PROBLEM. WIRING CK OK. ATHIRD ADI WAS INSTALLED. HAVE BEEN NO REPEATS.