First time FBL

[aww]

I’ve just built my first fbl heli (T-rex700n 3GX) and after setting up the 3GX it’s doing some strange things that I’m not to sure about. With the Tx and the 3gx set and powered up ever now and then all the servos give a small glitch, no set time or pattern. Also when moving the rudder slowly to the left or right the stick gets to aprox ¾ and the tail servo twitches. I’ve tested the servo on another channel and that’s ok so It’s coming from the 3gx. Any Ideas ?
Anthony

[sestcourt]

First time FBL

You could try reflashing the firmware... Do you know if its v3 or v2.1?

I had an issue when I upgraded from 2.1 to 3 and reflashing sorted the issues for me.

[aww]

You could try reflashing the firmware... Do you know if its v3 or v2.1?

I had an issue when I upgraded from 2.1 to 3 and reflashing sorted the issues for me.

It came with v1.2 and I upgraded to v3.0
Anthony

[coolice]

Hey Anthony.

What regulator are you using mate, is it an Align 6 amp unit?
If it is this could well be your problem, although it's bundled with the kit at 6 amps it is not powerful enough. Combine this with the fact that V3 now use's more power it seems and the twitching you are seeing could be from the power supply dropping.
When it's done this have you noticed any lights blinking on the receiver or satellites if you are using these connected direcly to the 3GX?

When powered for a little while have you felt any of the servo's to see if one is getting abnormally hot? If one is duff from the box this could also be pulsing the system and sometimes they show up to be bad by getting warmer than the other servos.

Let me know what your power supply is first and we'll go from there.
.

[old gimmer]

I have seen this happen where the servos were all twitching and it was the result of the satellites being DSM2 by changing to DSMX the problem was cured

[aww]

Yes I'm using the Align 2in1 and the reg lights do flash. I might try measuring the current draw with my Eagletree. I'm also using 2 spektrum DSM2 satellites.
Anthony

[simon_s]

The twitch on the tail is nothing to worry about. Both of mine do it.

[coolice]

Hey.

That may well be the cause, do you have another power supply you can connect to the 3GX, a 2s LiFe pack would be great as it would output a little over 6 volts direct.
Check the plug connections to, as a dirty contact can give similar power problems. In any case for a 700 class machine I'd recommend not using the Align reg.

Baring a faulty satellite the 3GX is fine on DSM2, it only binds in DSM2 mode anyway which is a shame for DSMX users.
.

[aww]

I seem to remember reading that there is a setting that allows you to reduce the current draw ( I'm no 3D pilot) or did I just imagine it?
Anthony

[coolice]

I seem to remember reading that there is a setting that allows you to reduce the current draw ( I'm no 3D pilot) or did I just imagine it?
Anthony

Hey.

Yes there is, by turning the gain pots on the 3GX unit to the 10 o'clock position or less. Apparently this reduces the current draw andpossability of brownouts on the smaller models running a low rated BEC.
.

[farmer]

Hi Aww,
Just wondered if you've solved the 3gx v 3.0 servo twitch problem. I am new to fly barless and building exactly the same heli as you (trex 700n 3gx) It came with version 1.2 updated to version 3 and I have now got the swash plate twitch When stood motionless without me touching the controls. I have tried the following to correct, a new 3gx, a new power supply, unplug servos individually with no joy.
The only way I can resolve is revert back to version 2.1 or if I unplug one satellite which is plugged into antennae 1, this resolves the problem with version 3 but I don't want to fly on one satellite.
Just to let you know I am using x spectrum dsmx satellite's and have exchanged one of those to see if that was the problem with no joy, have you managed to resolve yours in some other way?

Thanks Farmer

[aww]

Hi Aww,
Just wondered if you've solved the 3gx v 3.0 servo twitch problem. I am new to fly barless and building exactly the same heli as you (trex 700n 3gx) It came with version 1.2 updated to version 3 and I have now got the swash plate twitch When stood motionless without me touching the controls. I have tried the following to correct, a new 3gx, a new power supply, unplug servos individually with no joy.
The only way I can resolve is revert back to version 2.1 or if I unplug one satellite which is plugged into antennae 1, this resolves the problem with version 3 but I don't want to fly on one satellite.
Just to let you know I am using x spectrum dsmx satellite's and have exchanged one of those to see if that was the problem with no joy, have you managed to resolve yours in some other way?

Thanks Farmer

I’ve just got round to testing it. My Eagletree shows a peak of 2.5A and a drop of 0.2v when the twitch happens which would be about right for all the cyclic servos moving. I’ve re-flashed the 3GX with version 3.0 and gone thro a set up but the twitch is still present. When it does twitch I’ve noticed all the lights on the 2in1 flash! I’m now wondering if there is a way to data logging for the spektrum satellites (DSM2) It may be caused by the transmitter being too close. I’ve also just tried it with one satellite and yes the twitch has gone !
Anthony

[coolice]

Hey.

Using a Spektrum AR7000 or above receiver would allow you to plug the Spetrum Data module in to watch for antenna fades, holds and failsafes.

However from what you've said above I'd say it sounds like you have a dodgy satellite or cable going to it perhaps swap the sat you took off with the one thats currently on the model, using the sat connecting lead we know works.
.

[AlastairC]

First time FBL

On my 450 if I have the heli and tx closer than ~1metre then power up I get twitches from the servos. Further away no probs.

[aww]

I've also noticed that the tail twitch is linked to the gyro gain in head holding mode. 58% and less no twitch, 59% and above twitch when you move the rudder stick slowly. The higher the % the nearer to centre position it twitches i.e. 72% about 3/4 stick 95% 1/3 stick.
Anthony