What was found
PHL - FLT 1264 - AT APPROXIMATELY 400 FT, THE PRESSURIZATION AUTO FAIL LIGHT ILLUMINATED. CREW SWITCHED OVER TO STANDBY MODE AND COULD NOT CONTROL RATE OF CLIMB IN CABIN. CREW THEN TRIED MANUAL MODE AND AIRCRAFT STILL WOULD NOT PRESSURIZE. FLIGHT RETURNED TO FIELD AT PHL AND LANDED WITHOUT INCIDENT. NO EMERGENCY WAS DECLARED. MAINTENANCE REMOVED AND REPLACED THE E/E PRESSURE REGULATING VALVE AND THE RIGHT PACK FLOW CONTROL VALVE PER MM. OPERATIONAL CHECK GOOD. (M)