Rotary Knob for the FUTABA Transmitter
by Tim McCarthy

1) This system is for FUTABA only. Airtronics and Ace require a slightly different system

2) The electronic circuit shown will allow one channel to have a rotary knob.

3) Remove the back of the radio and disconnect the battery. Unscrew the four screws on the face of the radio that hold the gimble in place.

4) Note that there are three wires going to each pot on the gimble. The two outside wires are red and black while the center one is either yellow or orange. The yellow and orange wires are the signal wires. Cut the wires and remove the gimble.

5) Mount the rotary knob to the plate to the inside of the radio using 4-40 socket head cap screws.

6) The two 2K resistors shown in the above circuit can be replaced with adjustable trimmers set to 2K. Mount them to a small circuit board and adjust each to 2K and mark this point on each pot.

7) Simply wire per the diagram as shown.

8) Adjusting the 1K pot will determine the center position.

9) If you wire some other way, just remember to maintain the original resistance total across the circuit and correctly I.D. the power, ground, and signal wires from the original setup.