Servo jitters - SOLVED

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pandsrowe
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Servo jitters - SOLVED

Post by pandsrowe » Thu Feb 03, 2022 7:01 pm

Hi all,

I've tried searching for an answer but so far to no avail.
I have five deltang receivers fitted to the same number of locos all controlled from one Deltang transmitter, four work perfectly but one seems to be possibly faulty in that the two servos that it controls are constantly jittering. This occurs from the moment that the receiver is switched on, both servos start to jitter. They both respond correctly to transmitter commands i.e. forward/reverse and regulator open/close but all the time they are both exhibiting these constant jitters. Not only is this making quite a noise it also increases battery drain.
Anyone got any ideas or is the receiver faulty? I'm sure it has no bearing on the matter but the receiver in question is fitted to a Roundhouse Karen.
Phil

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Re: Servo jitters

Post by philipy » Thu Feb 03, 2022 8:07 pm

Can't help diirectly Phil, but there was quite a lengthy thread a few years back re jittery servo's, don't know if anything might help:
https://gardenrails.org/forum/viewtopic ... ilit=servo
Philip

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pandsrowe
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Re: Servo jitters

Post by pandsrowe » Fri Feb 04, 2022 9:34 am

Thanks for that Philip, I've only had a quick look but there does seem to be some useful content.
I will report back with anything I find.
Phil

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Re: Servo jitters

Post by Phil.P » Fri Feb 04, 2022 9:35 am

I would work through the old thread, and see if anything there helps..

But first, I would try different servo's, just plugged to the receiver, but can be hanging off the model.

You need to break the problem down:

Things it could be;
Low receiver batteries.
Poor reception / shielded (or broken) aerial.
Faulty (just 'different') servo.
Interference within the wiring. - doubtful.

It sounds unlikely you have a transmitter fault, but you could try binding another loco to that Selecta position. - That would eliminate a transmitter problem.

Another transmitter thought:
How old is the transmitter battery? It might be getting a little low, which could potentially affect performance.

Phil Partridge
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Re: Servo jitters

Post by SimonWood » Fri Feb 04, 2022 12:16 pm

Bit naughty of me, I didn't update the original thread to say what solved my problem: I did replace the batteries as Tom suggested, this did seem to resolve the problem.

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Re: Servo jitters

Post by pandsrowe » Wed Mar 09, 2022 5:55 pm

I can't believe that it's five weeks since I started this thread but today I finally got to the bottom of this problem. I won't bore you all with the details of how I got there but the jittering was caused by servo wires on the direction servo getting trapped under the loco body and partially shorting. For whatever reason this caused some kind of interference on the regulator servo as well, after replacing the direction servo everything is working just fine.
IMG_20220309_155733.jpg
IMG_20220309_155733.jpg (467.77 KiB) Viewed 13458 times
The photo hopefully shows the damage, I find it curious that everything was working albeit with jittering but I am just glad I finally got to fix it. Note to self - be more careful when reattaching loco bodies in future!
Phil

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Re: Servo jitters

Post by philipy » Wed Mar 09, 2022 6:37 pm

Well done in finally tracking it down. I know what its like when a problem is caused by something totally left field.
Philip

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Re: Servo jitters - SOLVED

Post by ge_rik » Thu Mar 10, 2022 9:28 am

That's a useful piece of info which might come in handy one day if that fault occurs again. I wonder if there's some way of flagging up your post to make it more prominent: I'll investigate. In the meantime, I can pin the thread to the top of the section and have added SOLVED to the title.

Rik
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Re: Servo jitters - SOLVED

Post by pandsrowe » Sat Mar 12, 2022 5:36 pm

Thanks Rik,
I thought that perhaps I should add a little more information as to how I finally solved the problem.
After Phil P's reply on Feb 4th I began by changing all the batteries for new but obviously that made no difference. Next I removed the loco body looking for anything untoward and was suprised to see that the receiver aerial is totally surrounded by the metal of the body and the running plate underneath, so in some respect its a wonder it works at all.
However next step was the purchase of a servo tester (I can't believe how cheap these are!) and this is where it got confusing. Initially both servos worked correctly so I assumed the receiver was at fault. I swopped this for one from another loco and then only the direction servo had jitters, the regulator servo was fine. In the meantime I had undone all the ty-wraps that Roundhouse had fitted that tidy and contain the wiring, my thinking being that maybe there was some electrical interference/pickup between the two channels.
It was at this point I discovered the damaged wires on the direction servo but what I didn't realise was the frayed insulation was in fact causing intermittent shorts and for some time I was chasing fault symptoms that kept changing, very frustrating!
Anyway, eventually I realised what had happened and from then on it was an easy fix, so in actual fact the servo itself was not faulty, just the wires feeding it.
Hopefully this might prove of use to others in the future.
Phil

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Re: Servo jitters - SOLVED

Post by Lonsdaler » Sat Mar 12, 2022 6:26 pm

Well done for persevering and chasing it down. Confusing symptoms with any issue can cause enormous frustration - it would be all to easy to give up on it. :thumbup:
Phil

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