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Servo Oscillation on start up

Posted: 07 Jan 2017, 19:48
by jimbo
Had a rather odd thing last few flights with a model and was wondering if anyone had seen it before.
On startup the left aileron would go into up down oscillation from endpoint to endpoint. Happpened twice now.
On the last time I moved the TX away and it cleared itself.
I then fully range tested it and then flew and it worked no problem, when i then moved the TX next to the model there was no such oscillation at any time. Flew the model and everything worked fine.

Is this the TX overpowering the RX or a servo issue, its a HS85.
Is the servo going into some sort of odd state, receiver is a futaba 617faast. Battery is of course fully charge.
Cheers,

Re: Servo Oscillation on start up

Posted: 07 Jan 2017, 20:23
by jimbo
Never happened before though. And when I put the tx next to the plane after start up it doesn't do it. Not sure what channel it is, but prolly 1 or 2 as its ailerons.

Re: Servo Oscillation on start up

Posted: 08 Jan 2017, 07:24
by Trevor
[quote="MarkDev"]Quite a common thing on my FrSky 2.4ghz set up, move the two, tx n rx, apart and they settle down with no more issues. Less than a metre apart and it happens again. I think this is common to 2.4. I expect someone will have a full explanation?

M[/quote]
If the receiver is swamped by the transmitter being close by, I call that bad receiver design. It's nothing to do with 2.4GHz operation, in fact I seem to remember seeing it rather more often in the 35MHz days.

Re: Servo Oscillation on start up

Posted: 08 Jan 2017, 11:00
by terry white
Hi Trevor,

What an excellent web site. Thanks for posting. I Hope to see you on the Purbeck slopes this year.



(Robbie, is it possible to arrange so this Webb site can be reached and viewed from the home page for future viewing?) Regards Terry

Re: Servo Oscillation on start up

Posted: 08 Jan 2017, 11:10
by Barry_Cole
jimbo wrote:Never happened before though. And when I put the tx next to the plane after start up it doesn't do it. Not sure what channel it is, but prolly 1 or 2 as its ailerons.
Jim,

I have heard this before, and the thought was that if Ch 1-2 were used for a bind plug, or shorting plug for setup.and it may be caused by the Rx checking to see if a bind plug is fitted.

BC

Re: Servo Oscillation on start up

Posted: 08 Jan 2017, 19:31
by Weds
[quote="MarkDev"]Quite a common thing on my FrSky 2.4ghz set up, move the two, tx n rx, apart and they settle down with no more issues. Less than a metre apart and it happens again. I think this is common to 2.4. I expect someone will have a full explanation?

M[/quote]

Wish this thread had turned up sooner, just swapped out servo, extension lead and eventually Rx to cure exactly the same fault on a Frsky system. didn't think it would be due to swamping signal.

Aileron servo would go full travel either way when operated. Did it at home under test and also on the flying field before launching, always at close range. Never thought to move away and try again..

Re: Servo Oscillation on start up

Posted: 09 Jan 2017, 19:34
by robc
Hi Jim,

Funnily enough I've just had a very similar problem with an HS85 in my Ventus, it appeared to be overshooting when using it through a receiver for the first time. I was going to replace it as it's not new but it seems to behave itself with a servo checker so I'm going to do some more investigation.

Rob

Re: Servo Oscillation on start up

Posted: 09 Jan 2017, 20:57
by jimbo
Rob I had a chat with Stan at the weekend on the hill. He explanation was that a small piece of carbon can get stuck on the pot on the servo, forcing it not to be able to centre. After a while the carbon moves out the way.
I have my reservations as it seemed to be related to tx position next to model. Further testing required here too.let me know how yuou get on.

Re: Servo Oscillation on start up

Posted: 10 Jan 2017, 10:21
by jimbo
Update - took my servo out of the model, stuck it on the servo tester - servo all over the place. New one ordered :(
Now are pots repairable? Gears looks good?

Re: Servo Oscillation on start up

Posted: 10 Jan 2017, 13:43
by RobbieB
jimbo wrote:'.............
Now are pots repairable? Gears looks good?
Jimbo, for the cost of an HS85 - lash it.

Re: Servo Oscillation on start up

Posted: 10 Jan 2017, 13:57
by terry white
Hi Jimbo.
I take it that you tried another servo in your servo tester just to verify that it is not the tester itself.

If it is as you expect that the pot is dirty ,or the wiper is not connecting properly then yes it can be cleaned and reset quite easily.

A job for deft fingers I would say, if God has given you sausages for fingers let some one else do the job! :lol: Or as Robbie says trash it. :cry:

Carefully strip the servo apart, checking how it all fits in to the small space inside the servo box. Lay out the gears on a piece of paper and mark how they each fit back in the gear box and on which splines.
locate the wiper pot and carefully unfold the tabs that hold it all together. You are now where you think the problem is. With a clean tissue or cotton bud dipped in switch cleaner (from Maplins) clean all around the area making sure you are not leaving behind any swarf yourself. Check as you put it back together that the wiper spring is in good contact with the carbon track and carefully adjust the spring if necessary.Replace as you dismantled in reverse. and Bobs your dads brother! Or if you have sausage fingers you could send it to me and I will do it for you. ;) Regards Terry

Re: Servo Oscillation on start up

Posted: 10 Jan 2017, 14:46
by Barry_Cole
Well, actually, Robbie said "lash it".

Maybe he was thinking of the Fawlty Towers moment.

:roll: :roll: :roll: :roll:

BC

Re: Servo Oscillation on start up

Posted: 10 Jan 2017, 16:14
by RobbieB
Barry_Cole wrote:
'...............Maybe he was thinking of the Fawlty Towers moment.

:roll: :roll: :roll: :roll:

BC'
Nope, more towards our husky based form of transport up here in the frozen northern wastelands. (Brian will enter stage right any time now.........)

Re: Servo Oscillation on start up

Posted: 10 Jan 2017, 17:39
by jimbo
[quote="terry white"]Hi Jimbo.
I take it that you tried another servo in your servo tester just to verify that it is not the tester itself.

If it is as you expect that the pot is dirty ,or the wiper is not connecting properly then yes it can be cleaned and reset quite easily.

A job for deft fingers I would say, if God has given you sausages for fingers let some one else do the job! :lol: Or as Robbie says trash it. :cry:

Carefully strip the servo apart, checking how it all fits in to the small space inside the servo box. Lay out the gears on a piece of paper and mark how they each fit back in the gear box and on which splines.
locate the wiper pot and carefully unfold the tabs that hold it all together. You are now where you think the problem is. With a clean tissue or cotton bud dipped in switch cleaner (from Maplins) clean all around the area making sure you are not leaving behind any swarf yourself. Check as you put it back together that the wiper spring is in good contact with the carbon track and carefully adjust the spring if necessary.Replace as you dismantled in reverse. and Bobs your dads brother! Or if you have sausage fingers you could send it to me and I will do it for you. ;) Regards Terry[/quote]

Thanks Terry,
Thatd be a job for a rainy day then.
As robbie suggests ive lashed it (lol) and ordered another one, its for my prize pace, so no point skimping on a model with a model 2 year waiting list :)
Jimbo.

Re: Servo Oscillation on start up

Posted: 10 Jan 2017, 17:40
by jimbo
PS Why isnt the quote working?

Re: Servo Oscillation on start up

Posted: 10 Jan 2017, 18:08
by Barry_Cole
jimbo wrote:PS Why isnt the quote working?
It is.....

BC

Re: Servo Oscillation on start up

Posted: 10 Jan 2017, 20:26
by jimbo
[quote="Barry_Cole"][quote="jimbo"]PS Why isnt the quote working?[/quote]

It is.....

BC[/quote]

Not for me!

Re: Servo Oscillation on start up

Posted: 10 Jan 2017, 21:40
by RobbieB
Jimbo,

I've been on this problem for a while now and not been able to track it down yet. It has happened to me once or twice in the past.

I'm in the process of preparing for a major update to the forum software that will, I'm informed bring some big changes as to how the forum functions, both from the user and administration aspect (we'll see........) so I'm hoping this will deal with this problem at the same time. I live in hope.

What is of far more importance however (to me anyway) is how the hell Terry knew my father had a brother named Bob!

Re: Servo Oscillation on start up

Posted: 10 Jan 2017, 22:17
by Barry_Cole
jimbo wrote:
Barry_Cole wrote:
jimbo wrote:PS Why isnt the quote working?
It is.....

BC
Not for me!
Does for me.....

BC

Re: Servo Oscillation on start up

Posted: 12 Jan 2017, 21:12
by jimbo
[quote="Barry_Cole"][quote="jimbo"][quote="Barry_Cole"]

It is.....

BC[/quote]

Not for me![/quote]

Does for me.....

BC[/quote]
Is that because you name is RED?

Re: Servo Oscillation on start up

Posted: 12 Jan 2017, 21:13
by jimbo
Update servo arrived. Fitted today. All sorted :)

Re: Servo Oscillation on start up

Posted: 14 Jan 2017, 16:06
by Bernie
come on Jimbo

don't mention Red - or - pink - you will only start him off again :D


Bernie :twisted: :evil:

Re: Servo Oscillation on start up

Posted: 14 Jan 2017, 19:43
by jimbo
Bernie,

Pink Taranis :)