Servo Twitch Problem

Hello, I have been trying to set up my trex 550 for about a month now and cannot get past servo issues. I have been using the APM 2.5 for about two years.

Ive got Align 615 servos in the swashplate and Align 655 on the tail. I have been trying to set it up on the bench powered through the 3DR power module, and the servos with a 5 amp BEC. I know a lot of people have talked about power issues, but I have tried to use HS55’s for testing and get similar results,
Radio gear- I am using a DX8 with DTFUHF. I have tried PPM in, PWM in, and the spektrum RX but not much changes.

When I power on, the servos go to center but I get twitching when I give inputs-- significant twitching (+/- 20 deg). I have been trying to use v3.1.3

If anyone can help me through this I would really appreciate it. I am getting very tired and giving up on the system :frowning:


Please provide either tlogs and/or data flash logs to help troubleshoot your issue.

are the servos twitching when you are not giving commands?

Is the tail drive system a drive shaft or belt? If you have a belt system you may have a Van de Graaff generator creating electrostatic charge and interfering with the signal to the servos. I had a similar problem a few years ago using an older flight stabilization controller on a helicopter. As soon as I would speed up it would start twitching. It helped when I grounded the metal boom to the gas engine but didn’t solve the problem. If you do have a belt driven tail I believe there are drive shaft conversions available and I would highly recommend it.

However, if you do have your log files post them so others can take a look to see if there is something else on the control side causing the twitching.

Is this the same mklinker as Klinker Aerospace?

Can you also provide detail on how the servo wiring is done? Also, could you try unplugging the telemetry radio and see if the twitching stops?

+1 on the telemetry radio. I had a lot of servo twitching until I relocated it

the telemetry can be the problem. Sometimes the servo itself will pick up the interference from the telemetry, mine has this issue, and is solved by relocating it.

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I had this problem with a bad batch of 615 servos when passing through center position. To me it seems unrelated to your system (i had it on the 3gx). I get replacement 615 servos and have been operating ever since without a problem.