Three servo glitch

[Ashley Davis]

Trying to track down an electrical issue.....

So far eliminated the BEC & ESC.

Basically what happens is in the hover all three collective servos glitch together in unison. I have swapped BEC and ESC and the problem remains. So now looking at rx and servos as possible causes.....anyone seen anything like this before and can offer any advice, I'm swapping the rx Monday, so then all that's left is gyro/tail servo and the three collective servos themselves. This is 2,4ghz not 35mhz.

[Smoothound]

I'd certainly be looking at the Rx next. Simple swap out for a fix. Is it new or one thats been used for a while?

[Ashley Davis]

had it a while and it's had one knock, I have to change it to put the AR7100 in to test the DX7 SE. Will be interesting to see if it goes away after the change.

[David Drew]

Ash, if it's all 3 servos at the same time I would suggest it's the input from the stick - stop drinking, you're glitching !!!!!!

David

[Ashley Davis]

it's bizarre as it's a proper really fast collective glitch. It's certainly one bit of electronics causing some serious feedback and the glitch, could be any one of the servos, the gyro or the rx at this point...... OR.... I've got a shorting wire somewhere.

[moyesboy]

I presume you are not getting a flashing led on the rx?

For all the servos to move together and equally:
There are certain circumstances where the rx drives all the servos to the positions where they were at bind (normally it just closes the throttle and leaves everything else at hold). It is worth making sure you bind the rx with the collective at neutral and throttle closed -otherwise the likely scenario is either full negative or a fair amount of negative. Perhaps that is what you are seeing? The -4 degrees you have in normal with the left stick down?

I think the scenario is a complete loss of rx power, that comes back again.The complete power loss (compare to a less than 3.5v dip) means the rx can't remember the control positions to hold, so it goes to the bind positions while it looks for the tx signal and links up. i think with quick connect this could occur very quickly, and repeatedly. but you should get a flashing LED just like you do when you switch batteries without power cycling the tx.

Static should be a bit more random (you have experience of that) and your 720 might give you a warning LED too.

[Thomas]

Is it just the cyclic servos or the rudder too? if it;s just the cyclics then it may be the TX

[Ashley Davis]

happens on two tx, I don't think I'm getting a flashing LED on the rx (I think I would have noticed) but I'll check.
I actually suspect it's something to do with the servos but I want to eliminate everything else first.

[scallybert]

[...]

Yes.

It is worth making sure you bind the rx with the collective at neutral and throttle closed

Yes, but bear in mind that the throttle channel is handled differently from other channels.

As you say, other channels send pulses at the bind value between init & connect.

Throttle sends no pulses until connect, when it sends value from Tx.

If connection is lost, throttle sends bind value pulses.

As I've bored everyone already, static caused me a load of strange problems, and is something I'd eliminate. Looking at the Rx LEDs is good advice.

[Ashley Davis]

I know it's not static......no flashing LED on the 720 gyro.

[scallybert]

I know it's not static......no flashing LED on the 720 gyro.

This might sound pedantic, but that tells you that the 720 hasn't detected a static problem; not that there isn't a static problem.

If it was flashing, it would tell you there was a static problem, but the reverse doesn't necessarilly follow.

If the 720 logs power failures/brown-outs, a similar argument would apply to BEC/power issues.

[Thomas]

You could try...

http://2.4gigahertz.com/systems/futk9200.html

[SRH990]

I'd substitute the receiver first, I had a similar experience, although with only one cyclic servo and expected that the servo was on the way out so substituted a known good one - and it still did it I swapped the receiver, a 6100, for another and the problem stopped altogether.

With three servos glitching it's more unlikely that it's the receiver but it's an easy test to swap it.

[Ashley Davis]

yeah, this was also my thoughts but I know of another flier with exactly same servos and he's also getting a three servo glitch.....so it's playing on my mind. However, the easiest check is to swap rx rather than swap all the servos.

[moyesboy]

I know of another flier with exactly same servos and he's also getting a three servo glitch.

...i'm sure you would have said if that was on a different radio system
sounds like rather damning evidence for the servos and if they are to blame I'm sure you will let us know what brand they are!

Try putting ferrite rings on those three servo leads? Or maybe putting a CL1 between them and your rx?