What was found
AFTER TAKEOFF, FIRST OFFICER'S NR 2 HSI HAD OFF FLAG. AIRCRAFT RETURNED TO KPDX. WHILE ON GROUND NR 2 RMI FAILED AND NR 1 HSI FAILED, BOTH COMPASS SYSTEM HAVE OFF FLAGS. PERFORMED SYSTEM COMPASS CHECK FOUND NR 2 SYSTEM CHECKED GOOD, CAPTAIN'S AND FO'S RMI CHECKED GOOD. REMOVED AND REPLACED NR 1 SYSTEM DIRECTIONAL GYRO. PERFORM SYSTEMS CHECK, OPS CHECK GOOD.