I have a hitec receiver in my EZ p-51 arf. Today at the field, I could not get any of the servos to respond to the transmitter. I made sure they were on the same channel and that the servos were getting juice from the battery. I could see the servos twitch for a second when I initially turned on the switch, but the plane would not repond to any inputs from the controls. This receiver has been in 3 planes and I am wondering if it is just dead. What are some causes of this problem?