What was found
DURING CLIMB, THE CONFIGURATION HORN SOUNDED INTERMITTENTLY AND THE AIRCRAFT LOST PRESSURE. THE OXYGEN MASKS DEPLOYED WITH NO AUTO PRESSURIZATION FAILURE INDICATION. CABIN PRESSURE MANUALLY RESTORED AND THE AIRCRAFT DUMPED FUEL AND RETURNED TO NRT LANDING WITHOUT INCIDENT. REPLACED THE PNEUMATIC OXYGEN FLOW CONTROL UNIT, CABIN PRESSURE CONTROL PANEL, AUTO PRESSURE CONTROLLER, PRESSURE ALTITUDE WARNING SWITCH, AND AIR/GROUND RELAY. OPERATIONAL CHECK GOOD. EXACT PART CAUSING PROBLEM TO BE DETERMINED.