What was found
SUP - PILOT REPORTED THAT ON APPROACH NR 2 ENGINE WENT IN AND OUT OF FEATHER WITH TORQUE APPROXIMATLY 750 LBS, AIRCRAFT YAWED BACK AND FORTH, TORQUE GAUGE SETTINGS WERE SIMILAR TO AUTOFEATHER TEST ON THE GROUND. REMOVED AND REPLACED CIRCUIT BOARD A123 IAW AIM MAINTENANCE INSTRUCTIONS 24-01, OPERATIONAL CHECK WITH CREW GOOD REFERENCE BMM 61-21-00.