I don't know if this is normal, but I noticed this strange behavior with two of my Futaba 2.4G receivers R617FS (7ch) and R6004FF(4ch micro) consistently with Futaba 3004 and Tower-Pro SG90 micro servos.

this is what happens: If I keep the Tx off and cycle Switch-On-Off the Rx switch harness, with every ON, the servo travels to one of the end monotonically, unless it reaches the extreme. After that, it makes a 'Click' sound (poor gears grinding) with subsequent Off->On, but wont move. If I switch on the Tc, the Servo immediately goes to center position.

This really scared shit out of me. Is this normal ? I mean it can really damage you Servos ? This behavior actually caused to dismantle my glued Servo from the 'Foam' mount as I had put the Arm with the wrong (spuriously traveled) servo pinon position.


On the side note(may be wrong place), I have noticed my Tower-Pro SG9 (9 gram) micro servos doesn't fit the Arm in exactly 90 degree to the servo case. The Arm fits the pinion making at least 15-20 degree angle which I need to trim with at least 30% bias, loosing the throws by as much as 30%!! Is this again a normal stuff or just the cheapness of these Chinese clones ? One can live with them, but its nice to build a plane which has all the surfaces in right places without trimming, and you leave the trimming for those 'in-visible' artifacts.

-Ujjwal

It could be the fail safe function. When no signal is received, the failsafe may be kicking in and taking the servo to the extreme. I think you should be able to program that through the TX. Yes the servo will be damaged if it goes to the end .
The other possibility would be that the servos are bad. try swapping ?

The standard operating procedure is to turn on the TX before you power the RX. If you do it the other way, then the servo positions can be arbitrary OR would depend on the failsafe capability and settings.

Ensure that you have failsafe programmed, if you are planning to play more like this.  It is just better to follow the recommended procedure of turning on the TX first.

Thanks Gaurav/Anwar for the reply. I have not yet explored my Tx much as I was using only on the SIM till date. With my first Semi-scratch model on the anvil, I guess I fully explore that.

@Gaurav, Same behavior is exhibited even with the stock Futaba 3004 servo. My first doubt was that only. But even Futaba servos doing same, I doubt the Rx instead.