I am new to RC airplanes and just bought an ARF Kadet LT-40, and Futaba7C and a 4YF for a trainer. The problem I am having is the trainer cord does not make good contact and I loose the link constantly. I have joined a local club and the AMA. This is for my son who is 9 so I have already spoken to an instructor who will train him. I am worried about loosing the connection in flight and I or the instructor will not be able to help. Has anyone else seen this problem with these connectors and is there a solution. I am nervous to even fly like this.

Try the cord on a couple other transmitters. If you have the same problem, exchange it. If it's ok on other transmitters, it sounds like the socket on one of your transmitters could be the problem.

I'd like to hear what that means, when you say "I lose the link constantly."

When the instructor switch is activated, the student box should have control. The instructor holds the switch against the spring the entire time the student is in control.

When the instructor releases the switch, control with the instructor transmitter resumes. At least, that's the way it's supposed to work. With all that in mind, I don't understand why you would worry about not being able to regain control in flight. When the student seems to lose orientation, the instructor releases the switch, corrects the plane's attitude, and resumes the session.

Are you saying that control is lost, and neither box will control the receiver? If so, that sounds like a bad receiver, bad transmitter, etc. I would really hesitate to point first at the cord.

Or, perhaps I misunderstood.
Dave Olson

Yes the power to the trainer box shuts off and on as you move the cable. I got the cable off Ebay and I am beginnng to suspect the cable is the problem. Looking at the pins in the connector they apear to be a very thin small gauge. I suspect they are not making proper contact with the transmitter connector pins since they are so thin. Also the connector on the new 7C transmitter I bought from Tower is turned slightly sideways in the socket hole. This appears to be cosmetic and I don't think it is the problem. I guess what I am asking is if anyone has had a similar problem with the new Futaba trainer connector style and if it is a known issue.

are you aware that the trainer transmitter must be in the off position also.
have you been in contact with the club instructor yet for him to check it out ?
it sounds that dad is just as inexperienced as the student and knows just enough to get into trouble trying to fix a non existing problem since he only assumes this is how it should work.yes that statement of "loosing the link" is suspicous!
the hobby shop where you got it can help also !
tom

I will try hard not to flame, so yes I fully understand how to operate the transmitter in the trainer mode. I am a fully certified electronic techinican working on multi-million dollar silicon chip manufactuing equipment. I have been in this business for 17 years, so I fully understand electronics, expecially something as simple as an FM transmitter. I simply want to know if anyone else has seen this porblem where there is a very poor link between the two transmitters. Again, everytime I move cable around the power light on the trainer box flickers on and off. This indicates it is losing the link as I also cannot take control with the trainer switch when the trainer box looses the link.

I am planning on seeing the instructor in the next couple of weeks and I wanted to get this ironed out before the first session. No rush though if we have to wait in order for my son to have the best possible training with an air worthy aircraft.

if it was me.......I'd just order a brand new $12 (or whatever it costs nowadays) cord and be done with it. Because from now on you'll wonder if it will fail every time you use it.

I asked earlier, and I think this answers my question - when your student box loses control of the plane, you're saying you can't reclaim control of the plane by releasing the trainer switch.

Yes, it sounds like you have a bad trainer cord. Something really fishy, though, is responsible for not being able to release the trainer switch and take control of the plane.

Does the instructor transmitter you are using have a good range check? Any intermittents? This does not sound like an open in the cord. However...

One thing that occurs to me is the power circuit. The cord provides power from your instructor's transmitter battery to your student box; the student box uses the power to create the signals for your transmitter to broadcast. In the event that you are shorting the battery wires together when you twist the cord, that would (1) kill power to the student box, and (2) short your transmitter battery, killing the available voltage to your transmitter. In that situation, no signal will be generated or broadcast, in either trainer switch position.

If the above is the root cause, you can confirm with an ohmmeter and a little cord twisting. Actually, I suppose a shorted pair that carries the signal could likewise interrupt control.

Good luck,
Dave Olson

Thanks everyone for the replies, I finally figured out the problem. It turned out the whole problem was with the new 7C I bought from tower. Like I stated before the connector in the back was turned slightly sideways in the socket hole. This was preventing the cord from being inserted all the way into the socket. I took the 7C appart and straighted the socket and this time when I plugged the cord into the box it went in all the way and stayed firmly there. In retrospect this should have been so simple, but I was not expecting to have to open a new transmitter in order to fix it. On the other hand I avoided a potential crash situation without leaving the ground. Thanks again everyone for all your help.