Servo humming

[ricm]

Test for 'servo binding' by removing the servo from the model and activating it as you normally would with it installed. If the humming goes away then something in your model/ linkage set up is restricting servo movement. If not resolved then your servo will burn out as noted by TRUCKMAKER.

You could move the connection point of your cable or rod closer to the servo horn center screw. Mechanically, this has the same effect on the linkage as reducing the servo end points and might be a simple way to solve a binding problem if you have limited options with trimming/ set up.