What was found
(CAN) ON LANDING ROLL SPOILER INBOARD HYDRAULIC AND NR 1 ISO VALVE CAUTION LIGHTS ILLUMINATED -- INSPECTED AND FOUND SEVERE CORROSION ON ISO VALVE SWITCH CANNON PLUG AND SOCKET. R&R SWITCH AND CANNON PLUG, OPS CHECK GOOD AT THIS TIME. DEFERRAL INSPECTED AIRCRAFT AND NR 1 RUDDER ISOLATION VALVE. FOUND EVIDENCE OF ARCING AT NR 1 ISOLATION VALVE CONNECTOR AT RESERVOIR.RESERVOIR LEVEL SWITCH & CANNON PLUG REPLACED, OPS CHECK CARRIED OUT, AIRCRAFT RETURNED TO SERVICE.