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Old 11-03-2008, 07:17 PM   #1 (permalink)
steph280
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Default Setting Up the GP-750 gyro in T-Rex 250 kit

The Align GP-750 heading lock gyro that is included in the new T-Rex 250 super combo kits has setup steps that differ with most other gyros on the market. In order to take advantage of its capabilities, correct options must be set according to the specific application. I will try to walk through the setup steps and explain each setting.

Similar to other gyros, when it is powered up, the LED will flash rapidly indicating initialization is in progress. Do not touch the gyro or helicopter at this point. Once the initialization process completes, the status LED will remain lit in green or red. Green indicates gyro is in heading lock mode, red means it’s in normal rate mode.

Before you start, it’s best to understand what each option means.

• 1520/760: This represents the frame rate of the rudder servo used. Most commonly used analog or digital servos use the 1520us frame rate. 760us rate is used specifically for high frequency servos such as Futaba 9256 and BLS251. If unsure, always set this option to 1520us to avoid burning out your servo. 1520us is also the factory default settings.
• DS/AS: This sets the gyro for either Digital Servo or Analog Servo. DS is the factory default setting.
• NOR/REV: This sets the compensating direction for the gyro.
• Limit: This setting limits the rudder servo travel and is used to avoid binding in the tail linkage.
• Delay: This is the setting used to dampen the gyro compensating speed for slower servos that are unable to keep up, resulting in tail oscillation. There is also an imbedded setting for the size of helicopter used. Small includes 250/450 size, while large includes 500/600/700.


The setup steps involve the use of your transmitter’s rudder stick and the “SET” button on the gyro. You basically cycle through the 5 options with the set button, and select the setting using the rudder stick.

• To enter the setup mode, press and hold the SET button for 2 seconds until STATUS LED flashes.
• While in setup mode, momentary press of the SET button will cycle through each of the settings.
• Select the setting by moving the transmitter rudder stick left or right, and observe the color of STATUS LED.
• When correct color is observed, press the SET button to memorize the setting.
• The gyro will exit the setup mode if left idle for 10 seconds.


Below is the walk through of an example setup. Suppose you will be using this gyro on a T-Rex 250 with Align’s DS420 digital servo.

1. Push and hold the SET button until STATUS LED flashes.
2. 1520/760 LED will lit up
3. Move rudder stick left or right and watch the STATUS LED. Green LED is 1520us, red LED is 760us. Let’s set it to 1520us.
4. While holding the rudder stick and LED shows green, press the SET button on gyro.
5. Now DS/AS LED lights up.
6. Move rudder stick left or right and watch the STATUS LED. Green is for digital servo (DS), red is for analog servo (AS). Let’s set it to DS.
7. While holding the rudder stick and LED shows green, press the SET button on gyro.
8. Now NOR/REV LED lights up.
9. Move rudder stick left or right and watch the STATUS LED. Green is for normal, red when direction needs to be reversed. Let’s set it to normal.
10. While holding the rudder stick and LED shows green, press the SET button on gyro.
11. Now Limit LED lights up.
12. Move the rudder stick and observe your tail pitch travel. Move the rudder stick left until the tail pitch slider reaches the end, then move to the right until pitch slider reaches the other end.
13. While holding the rudder stick, press SET button on gyro.
14. Now Delay LED lights up.
15. Move rudder stick left or right and watch the STATUS LED. Green LED is large helicopter, red LED is small helicopter. Let’s set it for small helicopter.
16. The amount of rudder stick moved from center will determine how much delay is applied. For this example, the Align DS420 servo does not need any delay, so rudder stick can be left centered.
17. While holding the rudder stick and LED shows green, press the SET button on gyro.
18. That’s it!
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Last edited by steph280; 11-07-2008 at 11:58 AM..
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