Single servo glitch with engine running
I am trying to solve a servo glitching problem with a wire braced biplane that occurs only when the engine is running. All connections have been made nylon to metal as far as I can tell--several things were done by a previous owner to minimize interference, but without success. The radio has always been rock solid when the engine is off, but then the servos jump when the engine runs.
The receiver was an old Airtronics, probably at least 15 years old. I tried a more recent Hitec, and the glitching was less. Then I tried a new JR 700. That ALMOST solved the problem, but the problem that remains is very strange.
With the JR, all servos are steady with the engine running except for the throttle servo. It occasionally blips and causes the engine to rev momentarily. It is not the engine--I can see the throttle servo twitch. Not all the time, just every now and then.
Two days ago, in a final ground test without the engine running, the Airtronics throttle servo suddenly failed. I substituted another servo which worked. The servo that failed will also not work with another receiver so it is damaged somehow. The new servo, a JR, functions completely normally with the engine off.
But with the engine running, the new throttle servo also glitches occasionally. I made one flight this way, and it happened in the air too. So I have a glitching problem affecting ONLY the throttle servo, no matter what servo or receiver I use, and one perfectly good throttle servo suddenly self-destructed. I doubt that it is just a coincidence. Any idea of what is going on?
Jim