What was found
INADVERTENTLY DEPLOYED ADG DURING GEN 1 CAUTION. AROUND 220 KNOTS ADG RAN FOR APPROXIMATELY 20 MIN IN FLIGHT. APU GEN WAS ON MEL, PILOT CYCLED WRONG GEN SW. RETURNED DUE TO ADG DEPLOYED. IDG 1 CAUTION MSG ON T/O AND THEN MSG CLEARED, THEN RECEIVED GEN 1 CAUTION AFTER APPROXIMATELY 5 MIN, C/Q QRH. AIRCRAFT REMOVED FROM SERVICE. RESTOWED ADG, PER AWAC SUPP 16-015A. OK FOR SERVICE, REF 306638/4 FOR NDT DIL. C/W AMM 05-51-19-06 INSPECTION OF ADG, REF 306639/3 INSPECTED AND FOUND NR 1 IDG OIL LOW, FOUND LEAKING AT FILTER ASSEMBLY, OIL OUT PORT. R & R "O" RING FOR FILTERS OUT PORT IN REF TO AMM 24-12-05. SERVICED NR 1 IDG OIL REF AMM SUPP 16-364, LEAK AND OPERATIONS CHECKED NR 1 IDG, IAW AMM SUPP 19-165. OPERATIONS AND LEAK CHECK GOOD. A/C OK FOR RETURN TO SERVICE.