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twitching servo

Old 06-13-2011, 04:14 PM
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tech1wi
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Default twitching servo

I have an old 7U Futaba. (Radio works perfect on another plane.) I have dual ele servos set up on GP Reactor. I mixed chan 7 w/2. When I work rudder back and forth the left ele servo twitches back and forth,, Why. When I turn off mix so only right ele is working , the left ele still twitches when operate rudder. I tried diff receiver and servo. still didn't fix. What am I missing?? I'm using cs-35 hobbico high power mini servos. Any ideas would be greatly appreciated

Thanks
Old 06-13-2011, 04:43 PM
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Default RE: twitching servo


ORIGINAL: tech1wi

I have an old 7U Futaba. (Radio works perfect on another plane.) I have dual ele servos set up on GP Reactor. I mixed chan 7 w/2. When I work rudder back and forth the left ele servo twitches back and forth,, Why. When I turn off mix so only right ele is working , the left ele still twitches when operate rudder. I tried diff receiver and servo. still didn't fix. What am I missing?? I'm using cs-35 hobbico high power mini servos. Any ideas would be greatly appreciated

Thanks
I used to have a 7AUPS. Do you have Ch2 as the Master and Ch7 as the Slave?

If the Elevator servo, on Ch7, twitches when the Rudder Stick is moved, you either have another Mix that couples the Rudder Ch4 with Ch7, or you have some RF noise, generated by the Rudder Pushrod, that is affecting Ch7. There could be other causes, as well, but those are the things to check first.

Pick an Unused Model Memory, Reset it to Factory Defaults, and see if moving the Rudder Stick still makes the servo, on Ch7, Twitch. If it does Twitch, then you need to look for Metal to Metal contact or if you use Carbon Fiber Pushrods, look for Rubbing there. These are some of the events that can generate RF Noise.

If it does not Twitch, then you must have had some Mix enabled that coupled Rudder with Ch7.
Old 06-13-2011, 06:40 PM
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tech1wi
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Default RE: twitching servo

Rich, I do have chan 2 as master and 7 as slave. I tried unused memory and reset to factory defaults. Same issue. The rudder servo is mounted externaly w/ about a 6" wire pushrod. No metal to metal contact. Actually tonite chan. 7 elevator was twitching w/ throttle movement also. I disconnected pushrod from throttle servo, so no mechanical connection to engine and same problem. I've been fighting this issue for a while now, very frustrating to say the least. Maybe time to upgrade my radio??
Old 06-13-2011, 06:46 PM
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Default RE: twitching servo


ORIGINAL: tech1wi

Rich, I do have chan 2 as master and 7 as slave. I tried unused memory and reset to factory defaults. Same issue. The rudder servo is mounted externaly w/ about a 6'' wire pushrod. No metal to metal contact. Actually tonite chan. 7 elevator was twitching w/ throttle movement also. I disconnected pushrod from throttle servo, so no mechanical connection to engine and same problem. I've been fighting this issue for a while now, very frustrating to say the least. Maybe time to upgrade my radio??
I agree it must be frustrating. If you have changed receivers and you still have the problem, it could be a glitch in the transmitter.

If you disconnect all servos except the Rudder and Elevator, do you still get the twitching?
Have you routed the Rx Antenna so that it immediately exits the aircraft and does not pass by any servos or other moving parts, including the Switch Harness?
Old 06-13-2011, 07:08 PM
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tech1wi
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Default RE: twitching servo

When throttle servo unplugged, it dosn't do it. I plugged in new servo and then acted up again. Now I'm really lost.?? Could it be the high power hobbico servos?? Ive never used these before. The antenna is routed outside plane.
Old 06-13-2011, 07:17 PM
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Default RE: twitching servo


ORIGINAL: tech1wi

When throttle servo unplugged, it dosn't do it. I plugged in new servo and then acted up again. Now I'm really lost.?? Could it be the high power hobbico servos?? Ive never used these before. The antenna is routed outside plane.
You did not say what type of Receiver Batteries you were using. If you are using 6v (5 cell) NiCad or NiMh, some servos are not compatible with that voltage and they will be erratic. If you switch to 4.8v (4 cell) and the problem goes away, you can use a Voltage Regulator or switch to servos compatible with 6v. If you are using unregulated 2cell LiPos or LiFe batteries, anything can happen.
Old 06-13-2011, 07:21 PM
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tech1wi
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Default RE: twitching servo

4 cell 4.8v 2000mAh receiver battery.
Old 06-13-2011, 07:27 PM
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Default RE: twitching servo


ORIGINAL: tech1wi

4 cell 4.8v 2000mAh receiver battery.
OK!! Have you tried plugging the battery directly into the Receiver and bypassing the Switch Harness?
Have you tried another Transmitter on the same frequency?
Old 06-13-2011, 07:30 PM
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tech1wi
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Default RE: twitching servo

I will try that tomorrow, and let you know what happens.
Thanks for the help.
Brian
Old 06-13-2011, 08:21 PM
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Default RE: twitching servo

I've had this problem before with a Futaba and traced it down to the brand of servos. Substituting Futaba servos for brand X solved the problem. Sorry, I can't remember the exact receiver and servos.
Old 06-14-2011, 05:06 AM
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Default RE: twitching servo

When Hitec introduced their 545 BB 5 pole hi torque servo some years ago, one gave me a similar problem which almost cost me a model.

Karol
Old 06-14-2011, 06:34 PM
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tech1wi
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Default RE: twitching servo

I tried plugging batt directly into receiver and a different transmitter. Didn't help.
Do you have any experience with the Futaba SR-10 servo reverser. Apparently it has RF noise filter built in. Maybe I'll try that. ??
Old 06-14-2011, 07:36 PM
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Default RE: twitching servo


ORIGINAL: tech1wi

I tried plugging batt directly into receiver and a different transmitter. Didn't help.
Do you have any experience with the Futaba SR-10 servo reverser. Apparently it has RF noise filter built in. Maybe I'll try that. ??
The SR-10 is a lower priced alternative to the MSA-10. It is designed to Match two servos on one channel. The JR Matchbox is similar to the MSA-10.

They are used more often when you need to sync two Flap or two Elevator servos, where one servo needs to be Reversed. I do not know if that will solve your problem. It may be that the servos you are using are not compatible with your receiver.

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