General No Power To Tail Servo

concodd

concodd

Member
I think I have solved the problem, but not sure how to fix it. I connected everything back up and went through all my alignments again right upto the rudder part. But again no movement in the tail servo. So I disconnected it. This time I left the connector cable (extended cable connector) in the 3GX and plugged the other end into the servo tester and then connected the servo to that. The servo worked perfectly. So the power is there and the cables are connected correctly but the message is not getting from the TX to that servo. Is there something that can be turned off in the TX that maybe not switched on that I do not know about??
 
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pvolcko

Well-Known Member
Does it make noise at all when plugged into the 3gx? even normal holding "chatter"? What if you try to change its position by rotating the servo horn? Does it fight you?
 
murankar

murankar

Staff member
Just for S&Gs take the tail servo and see if it will work in a slot for a cyclic servo. If the servo works then its good. Take a cyclic servo and plug it into the tail slot and see if the issue replicates itself. If the cyclic fails then it could be a gyro issue. It is possible that the signal pin may be broke some were in the gyro.
 
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pvolcko

Well-Known Member
It worked with the servo tester at the end of the video. I'm wondering it it is getting power at all via 3gx port and if so... Did you set tail servo freq setting? What type of servo and what freq did you select?
 
concodd

concodd

Member
Makes no noise at all, and no fight at all.

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The servo tester you see in the video is plugged into the rudder port on the 3GX and then the servo is plugged into the servo tester, as you can see by the blue light on servo tester , there is power coming from the 3GX. The servo is an MKS high speed digital and I set the freq to 760.
 
Graham Lawrie

Graham Lawrie

Well-Known Member
As suggested have you plugged the tail servo into one of the other positions? Move the tail and plug it into the pitch or aileron and see if it operates. That is the easiest way to see if it is faulty. I know the video showed it operating, but it would then point to possible gyro fault.
 
murankar

murankar

Staff member
That's exactly what I suggested. By moving the servo you can see if it truly is the servo or the 3gx. If it's the 3gx it sounds like the signal is faulty.

Sent from my LG-E980 using Forum Runner
 
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pvolcko

Well-Known Member
760 is usually a center pulse value (1520 is standard or 760 on special high speed tail servos, measured in micro seconds). The normal frequency for these 760 center pulse servos is 560hz. MKS is pretty standard on 560hz for servos with a 760us center pulse.

To verify, find your servo here: MKS Servos USA :: 760us/560Hz Rudder Servos

760us center pulse, 560hz frequency is what you probably want to set to. 3GX only allows setting the center pulse (760) so you should be good. Check to be sure, though. If you have a 1520us servo and send it 760us it will very likely damage it.

That all said, if the 3GX is able to power the servo tester off the rudder port, and it will actuate the servo, that is a pretty clear proof that the 3GX is not outputting a signal on that port.

Have you tried setting 1520us instead of 760us? If a standard servo tester worked (you didn't have to set it to 760us, did you?), that is making me think that this is not an actual 760us servo.
 
concodd

concodd

Member
On this servo tester there is a switch on the side for 1520 or 760. It was set to 760. The other 3 servos I have on the heli are 1520. I worry that if I put the tail servo in one of the ports to test it i will damage it. If there is a problem with the signal as you suspect, does that mean I have to purchase a new 3GX.
 
murankar

murankar

Staff member
Y o u should be able to change the That setting to match the servo.

If the signal line is broke more than likely it's in the housing. I have no clue as to his easy it would to inspect the circuit board.

If I had the money I would get a new one or invest in an ikon or skookum. They all should be about the same price.

Sent from my LG-E980 using Forum Runner
 
concodd

concodd

Member
Thanks Murankar, I have taken a chance with this one and just ordered another 3GX, they were on special for $100. Should be here in a couple of days. If the same problem arises then we will know it was not the 3GX and I will have gained a 3GX for a backup or my next project.
 
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