I bought an old Airtronics Infinity 6600 complete with 4 servos, RX, batteries, harness, etc. Operating PCM on Ch. 55. I'm still building the airplane but I powered everything up on the bench, including the aileron servo installed in the wing.
All 4 servos respond properly to commands from the TX but then they all begin "chattering". Vigorous, rapid, random, back and forth movement of the output wheels. They will sometimes stop chattering and behave normally, then start again randomly.
Has anyone experienced this problem and have an idea what causes it?
I haven't gone back to investigate yet. My only thought is that maybe I was overdriving the receiver. The antennas were only a foot or so apart.
I'll appreciate your thoughts.
Frank

Interference, fluorescent lighting, not turning on the transmitter first, nearby electric motors (freezer, fans, refrigerator, etc.), transmitter too close to the receiver.

Start there, take a few steps back.

getting too close to the receiver with the transmitter can cause the servos to chatter,even more so with the antenna fully extended.

You did make sure that the battery were fully charged, did you not? If you have the wall wart type chargers that come with most sets, charge for a full 16 hours. It is highly doubtful that having the transmitter to close to the receiver caused the problem. I have never seen that problem occur since they switched away from 27 MHz back in the 60's when they were using superhet receivers. None of the present day units are effected in that manner unless the receiver has become damaged in some manner.

It means your servos are about to implode, instantly destroying all matter in the universe.

Either that, or the other suggestions here.

Servos work by comparing two signals to each other. One signal comes from your Xmitter and is changed slightly when you move the stick. The other signal comes from the sevo itself and is altered as the sevo moves. A variable resistor or "pot" as they are called is mounted at the bottom of the servo motor. As the servo turns, this variable resistor is moved. THe signal in the servo is altered until it matches the signal from your Xmitter. When the two match again, the servo stops. It has a wiper and a coil, like a potentiometer. They wear out. The wiper oxidizes. The coil does also. The signal is sometimes lost and the sevo buzzes trying to align the two signals. Well, thats how old servos work. I don't know if they ever figured out a way to replace the mechanical pot with something else yet.
And as someone stated, standing very close to your airplane with the antenna fulling extended did sometimes cause chatter in the older radios. I haven't experienced that in a long time.


Make certain that you never route your antenna between your servos.

most likely you have the tx too close to the rx.. try setting it about 10ft way and turning it on and then the rx.

If your servos chatter when the transmitter gets close to the receiver, you have a poor receiver. That just does not happen with a decent receiver.

if all else fails use riddalin....lmao

HEY! Now we were doing good here.

a.) Nerves - they've seen you fly.

2.) They're girl servos.

III.) They're cold.

Frank,

You mentioned that you are using PCM. This type of transmitter uses CRC, or Cyclic Redundancy Checks.
While not going into the actual transmition and reception, i'll try to explain what can and cannot happen.

See, the transmition of signal from the transmitter to the receiver is coded, and if part of the signal is garbled, or missing, the receiver ignores that part of the signal, leaving the servo in the last known position. This is why having the antennas too close will NOT affect a PCM radio.

Low batteries can make the radios do very strange things.
Chatter is just one of them.
Inteference is ignored by the PCM system, so servo chatter/jitter is not caused by interference, unless it is another PCM radio on the same frequency nearby.
Flourescent lights will not affect a PCM radio.

Bad POTs in the transmitter, and bad POTs in the servos can cause chatter, but unless the transmitter was used in the rain, it is not likely that all channels would be affected equally.
A bad receiver can cause chatter in all servos.

I would recommend charging the batteries overnight and recheck it.

Let us know if that fixes it.

Here is a link with information on PCM vs. PPM if you are interested.
http://www.aerodesign.de/peter/2000/...M_PPM_eng.html

Bob

Thanks for all the input, guys. Helpful and interesting. Even the humor hit the spot!!
But, would you believe it, I can't reproduce the phenomenon. No more chatter. I have to think Rodney (in his first response) and bobmac010 got it right. The only thing I did differently was put more charge into the new 1100 maH flight battery. I still have no way to check "state of charge" (just getting started) of a battery.
I sure learned a lot about radio communication from this exercise and all the responses, expecially the comments from bobmac010 and the link to the German site.

Thanks all,
Frank