Quoted from pinhead59:Restoring to “factory settings” did not correct problem - thanks anyway. It was worth a try!
I am planning to remove the U6 EPROM and re-seat it. My old board did have the L4 rom installed. If re-seating does not work, I will try swapping with the L4 Rom from my original board.
Have you reseated the ribbon cables that connect the boards? Try a new cable or use deoxit on the existing one.