Question: What causes servos to make a noise when at "idle"?

 

Answer: This is nearly always caused by a stiff or sticking mechanical connection beyond the servo arm. The servo is trying to return to center when at idle and the mechanical linkage is impeding this so the servo keeps trying.

 

This puts a load on your servo, may cause wear and puts a high electrical load on your servo which will drain your flight pack more quickly than normal.

 

In the case of electrical RC systems that use a Battery Elimination Circuit (BEC) special consideration must be given to eliminating unnecessary loads from the servos. Firstly, such loads are depleting your only battery and this will lead to shorter run times and a early low voltage cutoff of power by the BEC monitoring circuit. Secondly, most BEC's are limited in the total amount of current that they can control. Adding more servos adds to the load. So does adding a bunch of servos that are all pushing on sticky mechanical linkages and working harder than they should. Some BEC's will shut down to protect themselves from overload. Other BEC's simply fail. In either event, your receiver will be without power and you will not be able to control the model if the BEC is not working.

 

Bottom line here is that you should make sure that all mechanical linkages move easily. To test for this we suggest that you remove the linkages from the servo arm. If the humming, buzzing or groaning noise goes away, then the mechanical linkage is binding. Straighten the path, make sure clevises, rods and other connectors are free to rotate in the servo arm holes etc. All control linkages should be slop free but move easily with a light touch of your fingers. Once you have the linkage freed up, reconnect the linkage to the servo and move the servo to and fro across the neutral position. Let the servo return to neutral. The noise should have stopped. If the noise is still present and you are sure that the mechanical linkages are not binding, you have another problem with the servo.