What was found
CREW REPORTED THEY HAD ELECTRICAL PROBLEMS. MX CONTROL ADVISED CREW TO RETURN TO BASE (MIAMI) A/C LANDED NORMAL, SECOND TIME TO RETURN TO FIELD FOR SAME ISSUES. MX REMOVED AND REPLACED AC BUS TIE RELAY, AC BUS SENSING RELAY, AND NR 1 T/R. RUN ALL 3 ENGINES, CHECKED PHASE'S ON GENERATORS, FOUND PHASE 'B' WAS UNDER VOLTS. PLACED NR 1 IDG ON MEL, IDG ASSY PLACED ON ORDER. A/C RELEASED FOR SERVICE.