Maybe I'm not understanding correctly - does it only look black with a certain CPS2 game? It might've suicided.
I still do not understand, when you switched "them" it worked, what worked, the monitor??, the cps2 game?? the A board? the B board?
When you turn it on and there is no screen, run the back of your hand across the front of the tube, do you feel static? If not the chassis may not be firing up. Check to see if you're getting back glow as well.