I have two k-line ep-5 engines and a Lionel gp-38. All three engines have Lionel tmcc. All the engines accept the program code and all the features work. The problem is that all of the engines go to full speed when you just turn the red button a little bit and they will stop when you just turn the red button backwards. There is no variable speed. I think the problem is with the motor driver board. Does anyone have a schematic of the board or any other ideas that might help. THANKS