Old 01-14-2005, 03:09 PM
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hilleyja
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Default Hitec Digital Servo Programmer vs Futab TX

Most of you are probably aware of this but I get the impression there are some out there that aren't.

Hitec and JR TXs center servo signal is 1500. Futaba center servo signal is ~1520. The Hitec programmer assumes center to be 1500. What this means is if you program the Hitec digital servo's centering only using the programmer it will not be correct when you use a Futaba TX.

Solution: (centering servo; 90 degrees to case)

1) Connect your servo either to an airframe or a test stand (Test stand mounts a servo within a protracter scale).
2) Connect the servo to the Hitec programmer and run the reset function.
3) Connect the control arm to the servo as close to 90 degrees to the case as you can get it.
4) Run programmer center function until the arm is exactly 90 degrees to the case and set the endpoints to approximately 100 on either side of the center value.
5) Disconnect the servo from the programmer and connect it to a powered-up RX and TX; make sure TX subtrims and control trims are set to neutral.
6) Take note of the direction and offset of the servo control arm. Make an educated guess as to the programmer adjustment needed. E.G., if the arm is about 4 degrees off center I would try an adjustment of 10.
7) Reconnect the servo to the programmer and rerun the centering function. Add or subtract your adjustment and set center to it. Reset the endpoints again to approximately 100 on either side of the center value.
8) Reconnect the servo to the powered-up RX and TX. Your centering should now be closer. Note again the direction and offset needed to refine it.
9) Re-run steps 5-8 as many times as is needed to come to a perfect neutral point for the servo.
10) Your centering programming is now complete (make no more center adjustments when adjusting endpoints later on.) and you are ready to connect the control rods and adjust the servo for deflections. Make no adjustments to your TX's subtrims because you will throw-off the programming -- this is especially important if you want 2 matching servos to a control surface to stay in sequence.

Solution: (deflections -- set required deflections for control surface or, on a test stand; 60 degrees; I will describe setting control surface deflections)

1) Connect your servo to a powered-up RX and TX; make sure TX subtrims and control trims are set to neutral. (NOTE: With my Futaba 9C, I set the TX endpoint deflections to 125.)
2) Connect your pushrod to the servo arm and control horn and manually adjust for neutral deflection.
3) Deflect the control surface 100% with the TX control stick -- take note of deflection angle or distance from neutral. How does it compare with the maximums recommended by the airplane manufacturer? Do this from both directions. Make an educated guess as to the programmer adjustment needed for endpoints, just like you did during centering. E.G., if deflection is 1/2" to short I will initially add 10 to the endpoint in that direction.
4) Connect the servo to the programmer and go into the centering/endpoint function. Using the setting you derived during centering programmer reset the center to that value. Add your adjustments to the endpoints and reset them using the programmer.
5) Re-connect the servo to the power-up RX and TX and deflect the control surface 100% with the TX control stick. You should be closer to the deflection you want.
6) Repeat steps 3-5 until your maximum endpoints are set to the manufacturers's maximums.
7) Further adjustment of deflection should now be done only with the TX's DualRate adjustments.

Any comments and/or inputs to these procedures is greatly appreciated. They have worked well for me. I do have to give much of the credit to Joe Hunt at downonthedeck.com for steering me in this direction. I give Hitec no credit because their instruction manual is woefully inadequate.
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