Tricopter tail servo not working (some query nobody asks before)

ArduCopter Copter 3.2
1

I have read all the threads on this issue, but no answer to my questions.

APM v2.5, Arducopter V3.2.1(confirm tricopter firmware loaded), 8-CH Orange Rx.

Connections as follows :–

Rx 1,2,3,4,5, 7 go to APM INPUT 1,2,3,4,5, 7.

APM OUTPUT 1 ,2, and 4 go to front motors and tail motor respectively.

APM OUTPUT 7 goes to tail servo.

I arm and spin the motors, and at the same time, I move the rudder stick, but no servo movement.

I have also set CH_7 Min to 1100 PWM, Max to 1900 PWM, and Trim to 1500 PWM.

I also confirm the tail servo works using another Rx.

Questions :–

  1. Do I need to set CH_7 OPT in Full param List (or Extended Tuning) to “Throw” (37) to activate the servo ? Full param list also says this function is working when PWM is above 1800 PWM. I tried this(set to THROW) , but nothing changed.

  2. Since CH 7 is not assigned to Rudder channel 4, (and I have not assigned any switch in my Tx to Ch 7), I don’t understand why the servo will move (as everybody manages to get) in response to rudder stick movement. This is supported by the fact that, Channel 7 green bar in Radio Calibration does not move in response to rudder stick.

Appreciate any help.