I had asked this question on another thread but got no replies. So here goes again.

What is the best way to test old servos, all of mine are Futaba or Tower.

I would turn the unplugged servo in both directions...check for roughness, weird noises, etc. Go to both extremes.

Then plug it in, and test it with the radio....check for noises, movement to end limits....grab it..test it to see if it will take a load.

Not very scientific I know....typically they work or they don't. It's pretty obvious if it's stripped. In the past I've had servos "chatter" after centering the stick...kind of like they're cycling. When they do this...I just toss them. Standard S3004s are about $16...not worth it. Besides, it's pretty uncommon for that to happen anyway.

Plug them in?

Besides connecting it up on the ground to a receiver and battery pack and turning on the bound radio to check it, here's a ten dollar servo tester that'll do some other functions such as a sweep etc. Also there is a link to another tester you can build with an explanation on what they do.
http://www.toysonics.com/esky-servo-...-ek2-0907.html
http://www.rc-cam.com/servotst.htm

If you have a tx like the Futaba 9c or 10C, not sure about others, it will have a servo test function that moves all servos to full travel on both extreemes. It will run as long as you want it to and is very useful in finding intermentent servos, although they will not be carring the flight load they normally would see.

I had a case a couple years back on one plane that the ailerons seemed to not stay trimmed, I sat the plane on a bench and ran the servo test for 30 minutes and the trim was still good at the end, then Iran another five minutes and applied hand resistance on the ailerons. It turns out that I had one servo that was "slipping" for the lack of a better term. Removed it and tied my dead servo knot in the cord and put it in the dead servo pile. Read servo spare parts bin.

I'm seriously thinking of one of the smaller "testers" listed above, if nothing else for setting upnew plane centers.

Don

These small testers are great for setting up new planes, they save a lot of time. I just bought this one and it has three functions: it centers the servo, allows you to manually move it end to end, and the sweep function automatically moves the servo back and forth until you stop it. It has a connection for up to 3 servos to test/set up at a time. I really added this to my recent Hobby King order since it was cheap and I wanted to see how useful it really was; it was $7 very well spent!

http://www.hobbyking.com/hobbycity/s...idProduct=8296

Thanks for all the info. I think I will add a model on my transmiter for testing and use one of my spare receivers and battery and do a basic function check as described by several of you.

Trying to burn in new Servos which I do on all of mine by letting them run in auto mode (which is continuously running from stop to stop) for about ten minutes each and also test crashed servos this way, is a major pain by trying to use a Rx. Best to get a real servo driver which can be had for as little as twenty bucks.

I have caught a number of bad servos both new and old by this burning in procedure.

A good driver is also invaluable in construction and installations of controls etc. Neutral can be found without the bother of hooking up a rx and runinng a tx.

John

There is a neat little gizmo from TXServo that connects to a computer USB port that does a very nice job of running the servos through their extremes. The software is programmable for a "scenario" that, once set, will put the servos through any set of movements you so desire.


http://www.txservo.com/

CGr

I've have one of the testers by Hobby King and it is great, sure saves a lot of time than having to hook up a rec. and xmit before installing a servo too see if it ok
wattmeter

One thing to bear in mind is that servos will have a definate "life". This is determined by wear on the mechanical components, in particular the motor brushes and the position feedback potentiometer. MG995 servos use a carbon pot that has a life of 5 minutes it seems.
Wear on the pot will present as failure to position accurately and consistently.
"Testing" the servos will only find these wear mechanisms when the servo is clapped out.

While blind installation of new or old/crashed servos without a simple burn in for a short period on the grounds that you are wearing out the servo may be acceptable to some however that premise is about as absurd as saying the same for breaking in an engine.

The original question was "how to test old servos" and the fact remains that inaddition to feeling for stripped gears manually running the servo in a continuous mode for a short period with a servo driver is an important part of that "test".

John

Am I supposed to bow to your greater experience or something?
I did not imply that testing servos would wear them out, so why did you infer it?
My point is that if a servo is nearing the end of its life, as in "How to test OLD servos", then a functional test merely serves to show that they are functional, at that time, and not that they only have a few hours left in them.
I agree that testing servos with one of these cyclers has the possibility of catching infant mortalities and that it will also find servos with damaged mechanics.

I give them a good visual inspection...then turn the output arm carefully by hand, (no power ) and listen/feel for potential gear damage...
Then plug 'em in and test for unusual noises/movement...using a servo tester.

I have a beat-up old trainer that I keep around just for testing old or used equipment..radios, engines, etc.


Edited to add: "using a servo tester" as mentioned by others in previous posts.

That sounds like an accident looking for a place to happen

That's the point...if it's going to happen, I'd rather it happen while testing in the trainer...which BTW is about 6 years old, and while the covering is tattered, and a little bedraggled looking, it's never been crashed.

I don't abuse my stuff, and very rarely have problems...but have been the recipient of several estates with lots of servos, engines, etc. etc. and I've given a bunch of them away...I want to know if they are airworthy first.

I don't bother with junk...just the stuff that passes the preliminary tests goes into the flying test bed.

This is the best tester for the money I have ever found. It is inexpensive and works great for testing a servo and also great for setting up a plane without a receiver!!!

[link=http://www.york-electronics.com/]servo cycler[/link]

Looks useful.
I think I might make one of my own.