Did you try restart, same thing?
Can be one of the caps gone dry!
Start with voltage check, then take a look over the board to see if you can see anything odd, know that vs board has allots of caps, depending on plonk sound it might differ!
Have you been moving the cab, or done something else that might losing some of the connectors, or harmed the main board?
I tried restarting it four times, same thing happened each time. The cab and the main board have been sitting still for several months. The cab hasn't moved in two years and the board was only moved once, which was several months ago when I took it out to swap the other side from Castlevania to SMB...but I played it several times since then and both sides worked fine.
Thanks for the info...if a voltage check is showing no voltage in some parts of the board, is it just a matter of changing a cap?