When I switch the power on, the servos (can't figure out which one) makes a buzzing noise, like it's not at rest. What do I need to do?

Unplug each servo in turn to identify which one it is.

Then remove the connection link to see if it is a servo fault or you have a stiff linkage. A stiff linkage is the common cause.

Digital servos are more inclined to buzz than analogue ones. It can be hard to stop digital servos buzzing. If the linkage is free I would not be concerned.

For me a quicker way to find which servo is buzzing is to grab my mechanic's stethoscope and touch each servo and the guilty one will will be found with ease. If you don't have a stethoscope, a long thin screwdriver will also work. Hold the screwdriver handle up to and touching your ear while you touch each servo with the blade end of the screwdriver. The vibration will transfer up the screwdriver shaft and buzz in your ear. Old race car mechanics trick.

Or just grab each surface and put a little pressure on it by hand. The noise will change when you find the one but as others have stated, if its digital it may do that at rest even if there's nothing wrong with it.

Digitalis? Servos can buzz from the weight of the control surface. Try lightly lifting the control surfaces if the buzzing stops your good to go

They are analog servos.

Then do as jdunker says. Find the servo that is buzzing. See if your servo linkage is binding

Not to be dense, but you are talking to a newbie. What is meant by "stiff linkage"?

Doug what is normally implied by the phrase 'stiff linkage' is simply the linkage somewhere between the servo and the flipper (control surface) is tight and too much for the servo to move or move without binding.

John

To take this a little bit further, since several have already explained how to find the offending servo, let's talk about checking the control surface and linkage. I would recommend taking the following steps:
1) Disconnect the linkage from the servo arm. Does the servo still buzz? If not, it's not a servo issue.
2) Check the alignment between the servo arm and rod end. If they are uneven, you need to realign the rod end. Reconnect the rod to the arm and test.
3) Disconnect the other end of the rod from the control surface arm and check the alignment. Realign the rod as needed and retest
4) If the servo continues to buzz, disconnect the rod at the servo arm and manually move the control surface. If there is dragging, disconnect the rod from the control arm and move the surface. If it moves easily, you have a push rod issue. If the control surface takes effort to move, you have a hinge issue that needs to be corrected

Just remember, it could be one of the above or a combination that is causing your problem

Thanks for all of the info! I do already know that the pushrods do not move fluidly. There is a tube that the pushrods go through. I guess the tube acts as guide? There's a little friction due to the pushrods moving through the tube. Maybe put a little WD-40 on the pushrods to reduce the friction in the tube?

Hi Doug

Are your pushrods wood sticks with wire ends? If yes then having the wire move through a tube is unusual and something I would not recommend

If the pushrod is a .plastic rod that runs inside a plastic tube which is fixed at both ends then these are usually very free running and I would look for misalignment or even physical damage before I would try lubrication.

I agree. I have never found lubrication of the pushrods to help at all. Sometimes pulling them and cleaning them (tube in tube) helps. Often you find that the inner rod has hardened some and taken a "set". Replace with a fresh inner rod that is flexible.

I have always found that buzzing means something is creating some drag or a bit of force on the servo. I like HJ's protocol, post 10. Unfortunately there is no spray can solution. You have to go through the linkage piece by piece and find the problem.

Jim

I like that term, "protocol". I have found that a systematic procedure makes troubleshooting easier. Eliminate something at each point and, eventually, you will find your problem. I learned to use a process of elimination from my father when I was very young. I still use the same basic process to this day and have never been failed by it