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Unpossible servo problem

Old 01-21-2011, 10:36 PM
  #1  
mclarkson
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Default Unpossible servo problem

I am building a wing and put all the pieces together today, but have run into a weird problem.

One of the two servos bounces and jitters, especially under small control inputs. (It does better at full extension.)

I futzed around with it for a while but got nowhere. So I replaced the servo with another 9g servo. Same problem.

I switched the wires for left and right servos. Same problem.

I made sure it was clearing the foam around the arm. Same problem.

I decided it must be the Rx. Replaced the Rx. Same problem.

The control rod goes thru a small tube on its way to the elevon, which seemed to be slightly off to one side, so I cut it loose to allow the control rod to just hang free. Same problem.

Seemed to be twisting a bit in its slot, so I went ahead and glued it in place. Same problem.

What. The. Heck?
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Old 01-22-2011, 12:00 AM
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CHELLIE
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What Transmitter, receiver are you using, Sounds like a RFI problem on 72MHz to me with a Cheapy Receiver. anyway, Put the receiver as far towards the rear of the plane as possible, away from the ESC, ubec, battery and servo wires, that should help, make sure the antenna wire is away from any servo wiring, things start to get cramped in a wing, and a cheapy receiver May not be able to filter all the RFI out.
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Old 01-22-2011, 12:50 AM
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mclarkson
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Chellie,

Interesting thoughts.

I am using my trusty DX6i, and a HK OrangeRx. The second OrangeRx came from my GWS Bipe where, while it has not been flight tested, it didn't exhibit any weird servo chattering behavior.

I just tried it now, with the Rx pulled as far away from everything as possible. I walked into the other room, 20 feet away, and could still hear it chattering.

If it's an Rx problem, when I swapped the AIL / ELE plugs, shouldn't that have transferred it to the other servo?

If I touch the servo at all, it starts bouncing around and chattering. The other servo doesn't display this behavior.

But, if it's a servo problem, shouldn't it have disappeared when I swapped out the servo?

I'm confuzzled.
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Old 01-22-2011, 01:02 AM
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CHELLIE
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interesting Problem, do you have the servo on a y connector, the y connector could be bad, or there could be a loose connection on the servo plug or at the receiver, I dont know how good those orange receivers are, do you have a spektrum reveiver that you can plug in, I have heard that 1 out of 3 of those orange receivers are bad.I know i would not trust them get a spektrum receiver to be on the safe side, I dont think you save any money buying knock off cheapy clone receivers.

Last edited by CHELLIE; 01-22-2011 at 01:17 AM.
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Old 01-22-2011, 01:14 AM
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this is what i read about the orange receivers from racer paul.

08:17 AM #15 RacerPaul
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Originally Posted by Larry3215
I followed the links but I dont see anywhere where you say if these are clones or not. Just that you test them.

So - are these clones or not? A simple yes or no will do just fine.

P.S. sorry if that came across a little grumpy. Im under the weather.
I think this answers that question....

"There is a lot of discussion on here about whether these are clones, knockoffs or overstock from the factory. "

I encourage everyone to read all they can on my threads and others regarding these products. As is stated in my other threads... the AR6100 receivers are as sold by oomodels and others and the Orange receivers are made by Hobby King.

One of the reasons I offer these is the high rate of unusable receivers experienced by purchasers from Hong Kong. Of my last shipment of Orange receivers, one third of them failed my testing.
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Old 01-22-2011, 02:21 AM
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Sir Crash-A-Lot
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Could be one of the other servos is bad also causing the other servo to chatter. Try unplugging all the other servos and see if it still chatters.

What servos?

Mike
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Old 01-22-2011, 03:03 AM
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mclarkson
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I appreciate the input from everyone.

I've determined that my replacement servo - a TowerPro SG90 9g from HeadsUp - is bad. I got 4 of these from HeadsUp for my TigerMoth 400 build and only used 3 at random. This one's been in its bag for months. I should have suspected the brand new servo!

However, I *think* I've resolved the problem, as the original servo - a T Pro SG90 9g from HobbyKing - now seems to be working.

My tentative diagnosis is this: Something was binding, causing the first servo to struggle. The second servo was bad, so continued to struggle even after I'd cleared up whichever problem was causing the issue in the first place. So I thought I hadn't solved the original problem when I had.

I hope.

There are several morals in here, I'm sure.

As to the OrangeRx issues, I have mixed feelings for sure, which is one of the reasons it's going on a foamboard wing rather than my F-27C.
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Old 01-22-2011, 05:09 AM
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glad you found the problem Take care and have fun, Chellie
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Old 02-11-2011, 04:13 PM
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That problem is quite often caused by a poor connection. Often just unplugging and replugging in a connector will cure the problem as the action improves the connection by abrading any corrosion on the connectors.
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Old 02-11-2011, 11:48 PM
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Originally Posted by mclarkson View Post
....I've determined that my replacement servo - a TowerPro SG90 9g from HeadsUp - is bad. I got 4 of these from HeadsUp for my TigerMoth 400 build and only used 3 at random. This one's been in its bag for months. I should have suspected the brand new servo!
....as the original servo - a T Pro SG90 9g from HobbyKing - now seems to be working.
....
Another possibility: Some individual servos require some "burn in". If you have a "servo cycler" device, running the servo back-and-forth, from end-to-end for 5-10 minutes can help "seat" the pot-wiper to the surface of the carbon potentiometer in the servo, and may smooth out the servo operation.
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Old 02-12-2011, 01:50 AM
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Hmmm... I may give it a try, if I haven't already chucked it. Thanks.
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Old 02-12-2011, 02:23 AM
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kyleservicetech
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Originally Posted by mclarkson View Post
Hmmm... I may give it a try, if I haven't already chucked it. Thanks.
Even if it starts working OK, being erratic is never a good sign. Would not use it in any critical surface, might be OK as a rudder servo. As for me, I'd sent it to the round filing cabinet located on the floor.
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Old 02-12-2011, 04:23 AM
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Every time I throw something away, I regret it in a week or two.
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Old 02-13-2011, 01:45 PM
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I have TP SG90's supplied with my 450 .... and one thing I noted with them ...

If a gear strips just a tooth or 2 - it appears to be ok - but when surface connected it jitters, jumps, stalls ... becomes a dog in fact.

I bought a set of replacement gears and found that the main output shaft diam has been changed ! I do not buy SG90's now .... the Mystery and other 9grs are cheaper and better !!
But the MG90's are in a different league altogether !
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