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Radio, servo malfunction

Haywire servos

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Robert Putley 119/04/2019 07:38:18
179 forum posts

Hi,

I have a new small scale electric areobatic model. All set up and ready to fly about a month ago. Thursday, took it down to the patch to maiden. Switched everything on. Cheched ailerons, next thing full port rudder, and ele moving around. Unoluged te Lipo., reattchedthe lipo, and again, same responce. Put that model aside and flew another.

Back home, same thing again. Tried another rx, no good. Same with a third.

So, next thing, wrote out a second model on the Tranny. Same response.t resort. tried another tx. same problem.

Left it alone to try the following day. Same thing, as expected. Then I disconnected the two aileron servos. Normal service resumed. Next, I connected two..different brand...servos to the aileron leads....NO problem.

The servos were unused,Tower Pro, which I thing I bought from Bangood.

What i do not understand is how when operating the aileron stick, is how these poor servos can affect the other controls.

Anone have any ideas.

Percy Verance19/04/2019 07:50:06
avatar
7793 forum posts
150 photos

Hi Robert

You tried several different receivers, so they can't all be faulty. But have you tried other types of servo?

I bought some small blue Tower Pro servos from a UK based supplier a few years back, and, as is my usual method, I plugged them into my servo tester 3 at a time for a 30 minute period. They got so warm I was shocked. I won't be using them in any of my models. Nor shall I be buying anymore. I replaced them with HiTec servos which were (stil are) fine........

Seems like a servo issue. You tried swapping everything else.....

P.S. I read it again. You did try another make of servo. I think you answered your own question Robert..... smiley

 

Edited By Percy Verance on 19/04/2019 07:51:53

Denis Watkins19/04/2019 07:57:32
3559 forum posts
166 photos

Have had one or two of the less costly lightweight servos do this Robert

Where the default setting was full deflection stalled, at the plugging in stage

Not worth messing with

If the servos work initially, this usually continues for their lifetime

Engine Doctor19/04/2019 10:50:45
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2197 forum posts
20 photos

They must make millions of these so a few dodgy one must creep in from time to time . As Denis says If they work from new, then they will usually last their lifetime without trouble You did test them before installation didn't you ?

Possibly the heavier current drian from the duff servo will affect the other servos ?

Doc Marten19/04/2019 11:09:12
172 forum posts
2 photos

Are you on 35 MHz?

Paul Marsh19/04/2019 12:46:34
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3582 forum posts
997 photos

Sometimes i found that the extension leads had caused problems with the servos, especially in the ailerons. Plugged them in, and both or one weren't working, or working weird, such as move the stick, the servo moves, then overshoots and flaps around central before stopping. Obviously, you can't fly that!

Simon Chaddock19/04/2019 16:38:12
avatar
5357 forum posts
2807 photos

Robert

A 'bad' servo may be drawing quite a few amps. This can cause the voltage to the rx to drop which may cause all the other servos to do strange things.

1. How many servos are you using?

2. What is the amps rating of the ESC BEC? if you are using one..

Percy Verance19/04/2019 17:36:33
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7793 forum posts
150 photos

Possibly another one to watch are those so called lightweight extension leads, made from very thin wire. These seemingly are rated for the smallest of servos only, and won't stand much current at all.........easily damaged delicate things they are.

gangster20/04/2019 14:24:54
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915 forum posts
16 photos

I don’t know if it is true but I have heard there are clones of tower pro servos about. I have had problems with one. In use for a couple of years no issues. Then one flying session no elevator on pre flight checks. Ele servo was so hot lower case was melted. Not sure if it was real or clone

Andrew Ray20/04/2019 14:54:44
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680 forum posts
19 photos

I had 5 Tower Pro servos from Banggood, they were all useless, they wouldn’t centre accurately and would overswing if the sticks were let go. Complained to BG who offered me some loyalty points (ha ha). In the end I told them I thought they were fake and opened a dispute through PayPay, they soon refunded the money and didn’t want the servos back so I binned them.

Steve Webb sells genuine Tower Pro servos, good vale and reliable when purchased from a reputable dealer who sells the genuine item. There is a lesson to be learnt there...

Robert Putley 120/04/2019 14:58:52
179 forum posts

Thank you for all your help. Firstly, I hard solder all my extension leads myself using heavy duty servo wire. Also the leads are not that long. Second, the radio is 2.4 Spektrum, six years of faultless service. Thirdly the esc rating is only 2.0 amps. I checked the Individual servos which for a 13gram unit have a very high current draw of 400 mah rising to nearly an amp. It would appear as suggested this was causing the problem.

So now I know the way forward, and thank you all for you input.

Robert Putley 120/04/2019 16:03:44
179 forum posts

I also purchased my 5 Tower Pro servos from Bangood, I would say around one year ago. Most of these stuff is rubbish so I now longer use them

Doc Marten21/04/2019 09:11:37
172 forum posts
2 photos

Posted by Robert Putley 1 on 20/04/2019 14:58:52:

...........Also the leads are not that long. Second, the radio is 2.4 Spektrum, six years of faultless service........

Interesting...I had the very same problem with Ailerons that fluttered like mad anywhere further than 10ft away from the model.

I was on 35MHz and using Corona servos which I had extended the same as you (soldered with decent wire) but they were very noisy, like you I tried various Rx's of the same brand, 3 same brand Tx's, I tried PPM and PCM, different battery packs, rerouted the aerial, just about everything but nothing cured it. In the end I took a chance and changed to 2.4GHz which solved it. I can only assume it was the noisy servos as when I tried the various setups without those servos it all worked fine.

Martin McIntosh21/04/2019 18:56:14
avatar
2772 forum posts
1034 photos

Not read all of this but I had a similar problem. Turned out to be the JR 591`s which will only work on 4.8V affecting the others. I was using 6V. I now use quite a few Corona servos on 6.6V LiFe packs with no problems.

Robert Putley 121/04/2019 19:32:56
179 forum posts

Doc Martin, that scenario sounds quite feasible. Friday, I ordered four new servos, different brand, different outlet.

Thanks to everybody for the feedback.

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