I have a Atari Asteroids Arcade cabinet that was left in my house when we bought it. It didnt work at first, due to a bunch of fuses being blown. I replaced them and it works. However the monitor will start to dim in the middle only when you play it more than 3 mins. And I cant see the whole screen, I can only see about half of the score at the top and I have tried the X and Y axis controls and even at max you still cant see everything. Any suggestions would be appreciated.

Actually I was playing it just now and noticed that the screen keeps zooming in. But if you leave it off for a while and turn it on you can see almost the whole screen. Any ideas.

I would check the Voltages at the plug going to the deflection board. But to help you more I would need to know what MOnitor you have and/or picture of it. but it sounds to me like your high voltage tripler is going out which is typical with this
game.