Spektrum TX/RX Troubles

by Don
(Park Ridge, IL)

I am having some issues with the electric RC plane I built. It's a House of Balsa T6 Texan (44" wing span). After the plane sat for a couple years, I decided to power it up to check it out. I am using a Spektrum DX6i with an AR500 receiver, 22 amp ESC, and 3-cell battery. Here is what happened:

1) The throttle was inconsistent. At steady stick, the RPM changes significantly.

2) I was also hearing an occasional knock during acceleration and deceleration. I still don't know what the sound is.

3) After 15 minutes or so, the throttle went to 100% on its own. Unfortunately, the prop was attached and ended up striking the receiver antenna. This, in turn, damaged the prop and motor mount.

After removing the prop and repairing the motor mount, I powered everything up to check it out.

4) Powered up the transmitter, then powered up the receiver. The elevator servo goes to full travel and stays stuck in that position (with some chattering). Moving the elevator gimbal barely moves the elevator from the stuck position.

I switched the elevator and rudder servo connections at the receiver. The rudder then goes to full travel and sticks. The elevator servo seems to respond in the rudder connector. It seems that whatever servo I connect to the Elev connector of the receiver, gets stuck at full travel and does not respond to input from the transmitter.

So, am I having a problem with the TX, RX, or both? Any assistance is GREATLY appreciated.

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Replace the RX
by: rcdude07

Please see my responses in line below:

I am using a Spektrum DX6i with an AR500 receiver, 22 amp ESC, and 3-cell battery. Here is what happened:

1) The throttle was inconsistent. At steady stick, the RPM changes significantly.

rcdude07: An electric motor does not spin at a constant rate. The magnets inside the brushless motor pulse to create the spins. The amount of time between pulse (0% and 100%) depends on the throttle stick position. But on a setup like this, you shouldn't be able to hear that (like the old brushed 1S micros from Horizon Hobby).
To me this would indicate an issue with ESC. Try a different ESC.
Or could be a loose magnet in the motor.

2) I was also hearing an occasional knock during acceleration and deceleration. I still don't know what the sound is.

rcdude07: Combine this with with your first problem and sounds like a loose magnet or something inside the bell of the motor hitting and causing issues.

3) After 15 minutes or so, the throttle went to 100% on its own. Unfortunately, the prop was attached and ended up striking the receiver antenna. This, in turn, damaged the prop and motor mount.

rcdude07:This would point to either an ESC issue or RX issue.
If the prop struck the RX antenna, the layout was probably wrong. The antenna needs to stay away from the motor, normally you want to run the long antenna towards the tail of the plane. And if there are 2 antennas, they need to be 90* to each other (i.e one running horizontal and the other vertial, or both vertical at 45* from the RX.

After removing the prop and repairing the motor mount, I powered everything up to check it out.

4) Powered up the transmitter, then powered up the receiver. The elevator servo goes to full travel and stays stuck in that position (with some chattering). Moving the elevator gimbal barely moves the elevator from the stuck position.

I switched the elevator and rudder servo connections at the receiver. The rudder then goes to full travel and sticks. The elevator servo seems to respond in the rudder connector. It seems that whatever servo I connect to the Elev connector of the receiver, gets stuck at full travel and does not respond to input from the transmitter.

So, am I having a problem with the TX, RX, or both? Any assistance is GREATLY appreciated.

rcdude07: The above section of text indicates the RX is probably having issues due to damaged antenna.

So in summary do the following:
1) check the motor for loose magnets and anything else causing rubbing issues
2) Replace the ESC
3) Replace the RX.

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