Found this tonight by total accident. I received my Champ last night, haven't even had the chance to fly it yet.
Anyhow, walked into the dark shop and I see an orange glow on the work bench. Thinking I had left the tx on I check and it's turned off. What the Heck? And just by accident I got the tx in the right position and I spied a little orange light glowing through the gap on the right side of the throttle switch.
Turn the tx on and the orange lamp stays on. Pull a battery and of course it goes off.
Now the weird part, tx is turned off, reinstall the battery and the orange light comes on and the tx makes 4 very soft beeps.
From what I can see the tx works fine with the bird. But for some reason something in the tx is staying on with the switch turned off.
I know I've read about battery problems and tx problems and wonder if this may be why. Would easily drain the batteries over time, and if something is staying on it could be causing something in the tx to overheat and act up.
I emailed Horizon on it and when I get a chance I'm going to pull the tx apart and see if I can find out what is going on.
But anyhow, you may want to look at your stock tx. I was lucky to find this as I doubt out in the day light I'd ever see it.