What was found
ON GEAR RETRACTION, HAD THE ATS TRIP OFF EITH UNSUCCESSFUL RESET. SHORTLY THEREAFTER PITCH TRIM NR 1 FAILED. SHORTLY AFTER THAT CABIN PRESSURE FAILED. NOTED ACARS DID NOT SHOW OFF OR ON TIMES. ACARS NEVER LEFT GROUND. PERFORMED PROXIMITY DETECTOR UNIT BITE IAW TSM 32-61-00, BOX LIGHT ON WITH FAULT ID CODES 23,24. REPLACED PROXIMITY DETECTOR UNIT 54GB IAW MM 32-31-71-04. OPS TESTED GOOD ON GROUND.