speedwings

Hello all. I have a Kadet LT-40 with a JR 631 radio system in it and I discovered a problem during it's first preflight this year.

The aileron servo works well when moved smoothly and slowly from one stop to the other. But when I abruptly select full deflection in one direction and let it spring back to center, it goes full scale deflection in the OTHER direction then returns to center. I also noticed that even when nothing is attached to the servo arm, it buzzes constantly and cannot be trimmed away. I plugged in two other servos on the airplane to that channel and it worked perfectly. I suspect that I simply have a bad servo and will replace it as soon as I get to the hobby store. But I have a few more questions:

What causes this problem?

Should I suspect the other servos could do this as well?

Is there ANYTHING else I should inspect in the radio system?

All of my radio equipment is just over 1 year old and this surprises me since I don't fly that much. Thanks in advance for the reply and keep 'em out of the trees!

JWN

My Feedback: (42)

I had a similar problem with a JR 4301 (?) several years ago. The servo was fresh out of the box. I sent it back to Horizon and they replaced it no questions asked. I never did find out what was wrong with it. I was just glad to have it replaced.

John

micboy

did you check the pod i think it is a bit dirty i had one i opend the servo and cleaned the pod it worked great..


hope it helps.

KJohn

My guess is that the chip that controls/drives the motor is out of tolerance for whatever reason. Maybe it got overheated at some point. Try it with NO CONNECTION to the ailerons and see if it stops buzzing. But don't use it in the plane in its present state.

If another servo works in place of it then most likely there will be no problems with the new servo in that application. But make sure there is NO BINDING taking place with the surfaces that are being moved (your ailerons). Binding could cause a servo to constantly hunt for center and keep the chip 'driving' the motor (the buzzing you heard). That could lead to overheating the chip I mentioned.

Good work with your pre-flight. That's why there is such a thing. It just paid off for you.

speedwings

Well, I cracked open the servo and didn't see anything amiss inside. After that, it worked great and I swapped it out with the throttle servo. Then I flew the airplane - no problems. Strange huh? I seriously doubt opening up the servo did anything so I have a new one one the way because I really don't want that servo shutting off my engine in a climbing turn right over trees.

Like we say in full scale flying, "Don't analyze it, just fly it!"

Thanks for the replies!