Futaba 9252 digital Servos Shudder with no load on them

[Scorf]

Hey guys/gals

I have always been a big fan of the futaba 9252 digital servos, flying mostly heli's for awhile now I started to get back into planes again. Here is the problem, I put 4 brand new 9252 servos in a 70 size profile and when I power them up they are fine but, if you touch any of the sticks on the radio it starts the elevator/rudder/ailerons etc into a non stop shudder while in the neutral position. If you add any input to them the shudder stops but continues when back in the neutral position. I have tried changing to a used set of servos along with the receiver and battery but, no difference. Does anyone have any ideas what may be causing this ? I forgot to mention, if you grab ahold of any of the control surfaces with your fingers, it stops !! You're input is very welcome !!

Thanks, Darryl

[Biff]

Hot charge on batts? I've seen this when I have just pulled a battery off the charger. They can be a touch nervous! Try a nicad with a partial charge just to verify.

[bodywerks]

If you are runnig a 6V pack without a regulator they will shutter with no load. Typically, once you put a load on them they stabilize.

[Scorf]

Sorry, I should have told you... 4.8volts not a hot charge. Used both types too.. Nicad and Nickle with no change. I know I know ... I'm screwed !!

[8iggles]

Were having the same problem....we have 4 futaba digital servo's (2 aileron 2 elevator) and an analog on throttle and rudder.....we have 6v nimh with no reg (will try on 4.8v as post above)
We've tried disconnecting them one by one but you can't pin it down to one - it just gets slightly better with each one you disconnect...One thing that worries us is the analog ones start twitching too!!
They do settle down after a while and also if you apply pressure to the control surface as was suggested.

We also have a kill switch as well and have had a couple of dead sticks - where we're sure the ign cuts and are not a fuel prob - You can start up straight away ???

Its as though they talk to eack other

Were using PPM receiver and our question is would pcm or the new intelligent (Multiplex IPD) make any difference or just mask the problem?

Thanks
Shaun and Ollie

[Kiwi]

Absolutely a PCM rx will make a difference.

I chased the same problem for weeks on my CA Fantasy with 6v pack and an FM rx.

The PCM rx fixed it in a jif but you need to be sure you have everything else right before throwing another 150 bucks worth of radio into it..

You will find any of the power expander, powerbox systems will do the same for you and you will have hardware to go bigger in the future. The problem is the pot in the servo is super sensitive. If you hook everything up and while its jittering take a finger and lift the elevator or an aileron. Does it stop on that servo. If it does you will fly OK as the airloads will stop all that from happening.

However for peace of mind some sort of isolator or power and signal conditioning system will cure all your headaches for ever.

Plus PPM receivers are are actually faster and more responsive than PCM. Plus PCM can and does mask problems with the model setup that PPM does not not.

Simple rule of thumb is if you have a problem with servos on a PPM rx and you fix it with a PCM you have not cured anything. You have just hidden it.

Kiwi

[8iggles]

Many thanks Kiwi

I have ordered the multiplex IPD synth receiver today, I have been looking at them for a while for the failsafe without going PCM....The read up says they learn your signal and only valid signals get through, they ignore any bad info...We have had a dozen or so flights with no problems apart from a couple of dead sticks (one was my fault slowing the tickover down too slow!!) so I'm confident were ok its maybe just us getting used to the twitches??

I can accept the digitals twitching whist under no load as they search for their position, but can't understand why they make the analog ones twitch too - the posts earlier make sense about the battery supply because this is common to all channels and whilst the digital servos are twitching maybe the votage is fluctuating??

Like you say a powerbox is the way to go

Thanks again

Shaun