Hi ,
One of my planes which gets an airing probably once a month has three servos in the fuz and one on the wing. The fuz and the wings are stored separately.
Today at the flying field I found that all three servos in the fuz were dead. When I got home I exchanged the servos for brand new ones. hey presto problem solved.
My question is what could cause all three servos to die? the one in the wing was Ok so it must have happened whilst the plane was in storage.i.e. the wing servo was not connected to the receiver. I use a 4.8volt 1800mAh battery pack could this have been left on and burnt out the servos. I have been aeromodeling about 18months and have never heard of servos burning out. Any explanation would be greatly appreciated.
Kairos.

This would seem to me to not be very probable that the servos could have been damaged by leaving the switch on, batteries yes, servos no. There has to be some other cause as such happening is very unlikely. Have you checked out the servos on another system or even on the old one now that you have the new servos working? Just plug them in place of the working ones, one at a time and they will probably work okay, just corroded contacts that got somewhat cleaned when you unplugged and replugged them. This assumes they were not in a fire or submerged in water or some such similiar happening.

Hi Rodney,
Thanks for the reply.After your message I plugged all three dead servos into another Receiver and still they would not work.At least two of the servos are stiff to turn (Never a good practice on new servos) but it did prove that internally something has tightened up.
The servoes don't even kick when turned on. The servos are Futaba s3003.
Half way through this message I have stopped to gut one of the servos! The motor seems to run free as a bird and all the tracks on the printed circuit board look OK but who knows what has happened to the components. All the gear wheels seem OK but of course they may have expanded a thou or two and become tight.The servo still will not run even with the gears removed.
I still can't fathom out what has happened. May be the best thing is to bin the servos and move on.I wouldn't use them now even if I could repair them.

Again Rodney thanks for your reply,

kairos AKA Richard.

Did you take an ohmmeter and check the continuity of the servo leads?
as long as you have the servo open, it would be simple to do.

I'm betting on bad contacts since you left the servos connected with the battery on. Is that the case?

If you find that the leads need to be replaced, it really isn't too hard with a 25-30 watt soldering iron.

I have a few servos well over 20 years old and no problems with them. Other than gears getting clogged with congealed grease or broken, there is very little that can be wrong other than a bad connection(s) somewhere.

Hi Jeff,
Thanks for the advise. I have checked all the leads and they are OK. You certainly started something though because I have now checked the resistance readings across the leads. A good servo seems to have red and black leads and white and black at
very approximately 140-150 K Ohms and white and red open circuit.

two of the dead servos have red and black in the milli Ohm range .
And the third has the white and black at 122 K Ohms which should probably still work but it doesn't!

Only this one plane has suffered the servo problem although I have two other planes in the same space in the attic which gets rather warm at times especially as July was the warmest July on record but of course this is UK! All very strange.
I think now it is all a bit academic but it would just be nice to solve the mystery.
thanks again for your input.
Richard.

Richard,
Now that you've checked the leads red to black and such check them again as compared to a known good servo of the same type.
And don't forget to check the leads end to end if you already have the servos open.

Also, if you get different readings against good servos and the servos are apart, check the suspect servos where the leads
connect to the circuit board. This whole exercise can eliminate any bad leads from the connectors to the circuit board.

Hope this helps.