What was found
AIRCRAFT WAS GROUNDED: FLIGHT RETURNED TO PHL ON ACCOUNT OF NUMBER ONE ENGINE OIL PRESSURE INDICATION. AN EMERGENCY WAS DECLARED. ENG 1 OIL PSI GAUGE WENT BETWEEN 100 AND 0 PSI AND THEN AMBER XX'S. IT WAS INTERMITTENT UNTIL LANDING. MAINTENANCE INSTALLED NEW OIL PRESSURE TRANSMITTER, NO HELP. DISCOVERED A LOOSE CONNECTOR, TIGHTENED CONNECTOR, NO HELP. REPLACED #4 BEARING OIL PRESSURE TRANSDUCER AND CONNECTOR 4005ENA, NO HELP. MAINTENANCE REPLACED THE SYSTEM DATA ACQUISITION CONCENTRATOR, ALL INDICATIONS RETURNED TO NORMAL. MAINTENANCE ALSO REPORTS THE SDAC WAS SWAPPED FROM 2 TO 1 AND CHECKED GOOD, AND WHEN PUT BACK TO ORIGINAL CONFIG. ALSO CHECKED GOOD. MAINTENANCE SUSPECTS THE FAULT WAS LATCHED INTO THE SDAC, HOWEVER THIS IS JUST A THEORY.