Thanks, John.
I examined the AC CDR, physically, and can see nothing wrong. Traces appear to be undamaged and there is no visible damage to any of the components. I attached a spare coil coupler directly to the board and a spare light bulb,
Back to the track, the locomotive starts and runs very well. The lights are changing with directions and the coupler does fire correctly. I guess this means that the Railsounds card has bought the farm. Fortunately, I see that 3rd Rail has them in stock.
Thanks to John and George for your help.