What was found
WHILE OPERATING HORIZ STAB TRIM ON CHANNEL NR 2 ONLY THE FOLLOWING OCCURS. PUSHING BUTTON ON CONTROL WHEELS TO NOSE UP, HORIZONTAL ACTUALLY WENT DOWN THEN DISCONNECTED. REPEATED ATTEMPTS, KEPT TRIMMING TO NOSE DOWN POSITION. COULD NOT GET HORIZONTAL TO TRIM NOSE UP ON JUST CHANNEL NR 2. ONCE CHANNEL NR 1 WAS ENGAGED HORIZONTAL STAB TRIM WORKED CORRECTLY. THIS PART WAS SENT TO THE MFG BY THE PREVIOUS OPERATOR FOR THIS EXACT PROBLEM. MFG REPLACED PARTS AND RETURNED IT TO SERVICE. PROBLEM REOCCURRED, UNIT REMOVED AND SENT BACK TO MFG. (K)