What was found
IN FLIGHT, LOST RT EMERGENCY AC BUSS, GEN BUS 3 FAULT ALERT. FOLLOWED THE QRH PROCEDURES, DEPLOYED ADG AND RETURNED TO DEPARTURE WITHOUT FURTHER INCIDENT. FOUND IDG/INTERFACE TRIM HEAD FAULT. FOUND CONNECTOR "A" PINS 8 & 7 OPEN. REPINNED. OPS CHECKED OK. AFTER CHECK OUT, HAD NR 3 TRANSFORMER FAULT. REPLACED NR 3 TR & GEN CONT RELAY, SWAP RELAY. ALL NO HELP. R2 APU GCU, NO FAULTS.