What was found
AIRCRAFT RESPONDED AS IN PREVIOUS WRITE-UPS AT LEVEL OFF FL330, PORPOISING /- 500 IN ALT HOLD, SAME RESULT AP 1 OR 2. DISCONNECTED THE AP AND SLOWED 20 KNOTS, AIRPLANE WAS DIFFICULT TO CONTROL, VSI /- 1000 FPM AND ALTITUDE /- 200 FT. DESCENDED TO FL 290, NO IMPROVEMENT. DIVERTED TO SLC. WHEN HYD PRESSURE APPLIED CHECKED ELEVATORS FOR MOVEMENT BY PHYSICALLY TRYING TO MOVE ELEVATOR SURFACES. NO MOVEMENT WAS NOTICED. CHECKED AUTO PITCH TRIM LVDT NULLS. FOUND CHANNEL A NULL TO BE 574 MVAC, JAM NUT WAS LOOSE ON THE LVDT. FOUND CHANNEL-B NULL TO BE 175 MVAC. ADJUSTED AUTO PITCH TRIM LVDT'S NULL. OPS CHECKED AUTO PITCH TRIM SYSTEM PER MM 22-22-00-5, SYSTEM TESTED NORMAL.