If the servos have some hours on them, the potentiometer is probably getting a bit dirty. I'd say give it a good cleaning, check to make sure there is no slack in the gears and go from there. Otherwise, replace it (them).
Here's an interesting read: http://www.helifreak.com/showthread.php?t=671470

 

Thanks @Beaver

I would also say its a dirty poti. The helifreak thread is a bit older. I have been trough this last year as I had problems with my Align tail servos.

My cyclics work great so far. Only this dithering appeared some flights ago. So I will pick the servo appart today to see if its dirty inside.

 

The potentiometer is a closed plastic unit. What should I clean here? Gears are running smooth. The connections on the servoelectronics look fine. There is no dust in there...

 

Problem solved. But I dont know how. I picked the servo apart had a look at everything, cleaned the gears just a bit, screwed it together again the poti mounted how it was and the dithering is gone now..

Back on the heli the swash is straight as I know where my servohorn was. I tested for around ten minutes even with my hand ond the head to sinulate some force. Works great even when i carry the heli around. Nothing.

What could have caused the problem?

 

That's a good question!

 

Maybe a speck of debris caught in a gear? Who knows. I'd keep a close eye on it at first. Last thing you want is a servo malfunction, as I understand that can be inherently dangerous.

 

Its possible that a plug connection be a touch dirty. Even sometimes reseating the potentiometer can help. But what i would carefully inspect the servo plugs if i were you. Sometimes the female receptor slips back into the housing and does not connect as well as it should. So i would really inspect the lugs to make sure they are seated right. Perhaps put some metho or contact cleaner on the female socket and wipe the male pins as well. Any form of resistance along the control or power wires to the servos can cause this sort of problem as well. I have had this happen many times on my servos and allways found the plugs to be the culprits...

 

Maybe @Crash Heligod is flirting with you @iggy.

 

Thank you @smakmeharder. I will check this today before going to the field for sure. Sounds logical.

@Beaver keep that guy with you its allright! LOL

 

Did four test flights this afternoon after checking the servo connectors too. Everything fine. It seems like the dithering really affected the flight behavior. The 570 feels better now. Im happy.

 

Glad to hear it!