Since its a JR then that means you should have to send it in to Horizon Hobby, and they have excellent customer service. I have sent in three different things for repair and they fixed all for free. If you bought the transmitter from a authorized dealer and its still under warranty then all you have to do is send it in with a invoice. If you didnt get it from a authorized dealer or its out of warranty then you can still send it in, but on a piece of paper write down all your info with a note on the problem and request a free evaluation along with a quote to fix it. They will check out the transmitter and will either call you with the problem to let you know the price to fix, or they might fix it for free if its a small problem.

I had to send my DX7 in after I accidentally stepped on the antenna and it broke off. I sent it in and they did a curtosy repair, free of charge.