What was found
FOUND NR 1 TRANSFORMER RECTIFIER FAULTED ON MAINT PANE (MULTIPLE FAULTS IN FLT- TRANSPONDER, AUTO-THROTTLE, PITCH TRIM). REMOVED AND REPLACED NR 1 TRANSFORMER RECTIFIER IAW AIRBUS M/M 24-32-11-4. OPS CHECKED NORMAL PER AIRBUS M/M 24-32-00-5. ALL OTHER FAULTED SYSTEMS TESTED OK. THIS BUSS PROBLEM APPEARED TO BE THE ROOT CAUSE, SEE 34-54/9169 (TRANSPONDER), 22-10/9170 (PITCH TRIM) AND 22-30/9171 (AUTO-THROTTLE).