if you boot up the machine does it "play blind"? IE, can you insert a coin and play a game and hear everything, just not see it?
if so, it's a monitor or power fault.
if not, it could be a board or power supply fault.
if it's a monitor fault, you will have to post what monitor it contains. take a picture of the boards and post them here and we can let you know where to go from there.