This is an FYI for those considering the Rottendog board for Black Knight. It appears there is a systemic problem with the board that many folks are experiencing - see this post
https://pinside.com/pinball/forum/topic/black-knight-ball-advance#post-4064472. The sound does not work and the ball in play will not advance when a ball drains.
Rottendog has acknowledged the problem but has not fixed it. I have received a flashed rom that did not solve the problem and most recently a new replacement board manufactured in October 2017 that has the same problem.