Rich,
The first two times mine went bad it was like you are describing. No display. The unit I am having problems with now still has the display but it shows
0 volts and 0 amps to the cell. Autopilot customer service said it was a bad cell cord. I replaced the cell cord and nothing changed so they said it was a bad power supply. For the price of the power supply I can buy an Aquarite with the cell and since my Autopilot cell is about 3 years old, it will probably need replacing soon. The volts to the cell were dropping all summer and like you, I'm not sure if it would have caused a premature end to the cell life. In your case, since you've already purchased a new cell, you would probably be better off just getting the new control board. My Autopilot worked GREAT when it was working. After owning a SWG I'll never go back to BBB.