What was found
PDX FLIGHT 2301: DURING CLIMB AT 220-230 KTS, OVERSPEED WARNING HORN SOUNDED. THERE WERE NO OTHER ABNORMAL INDICATIONS. AIRCRAFT WAS RETURNED TO FIELD. LANDING WAS NORMAL AND NOT OVERWEIGHT. THE OVERSPEED HORN SOUNDED 5 OR 6 TIMES IN AN INTERMITTENT MANNER. MAINTENANCE SUSPECTED THE WARNING HORN THAT SOUNDED WAS THE TAKEOFF WARNING HORN INSTEAD OF THE OVERSPEED WARNING HORN DUE TO -NGWOFW1 FAULT (L) PROX SENS OPEN- FAULT IN FAULT HISTORY OF PSEU. REMOVED AND REPLACED NLG WOW NR 1 HARNESS AND FUNCTIONAL TEST OF TAKEOFF WARNING SYSTEM. FUNCTIONAL TEST GOOD. NO FURTHER DEFECTS NOTED. AIRCRAFT RETURNED TO SERVICE.