I finally made the switch from a New Holland TR70 to a John Deere 7720. When I first got the machine home the digital display worked in the cab. Now it only shows 8888 and the green light is lit up next to all four buttons. Is the unit shot? Also, I don't have any operators/service manuals yet but the computer for the dial-a-matic controller is not in the machine right now, where does this go? Could this be related to the display problems?