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Modifying a Sail Servo to 180 Degrees
The Hitec HS-765HB Sail Servo is recommended for the Fairwind 900 model yacht but has only 90 degrees of rotation
- see
Bakersfield Fairwind for Racing. Adding two 2.2 k ohm resistors (red, red, red colour bands) to
the red and green potentiometer leads will give 180 degrees of rotation.
To avoid dismantling the servo and risking damage a servo stretcher can be
purchased or made on veroboard which connects between the receiver and servo and
has the same effect. These are rather expensive and I couldn't find the circuit
so I chose the dismantling option.
First apply electrical tape to both sides of the top half of the servo to hold the gear mechanism together
when the screws are removed. The motor is held in place by a blob of glue. Heat
may have to be applied with a soldering iron to the motor contacts to soften the
glue if the board cannot be removed by force. The potentiometer is held together
by a screw and three lugs which have to be carefully bent upwards. Ensure that
it is replaced in the same position. Both ends of the red and green wires are
glued which makes removal difficult so I cut them in the middle and soldered in
the resistors. I covered the joints in heat shrink and carefully flamed them
although electrical tape would have been easier and just as effective.
So why can't Hitec make this alteration and put a switch on the side for both options?
David Barlow
davidbarlow17 at yahoo.co.uk