Response from Jonathan: Dave,

Nope, probably not a degaussing issue if it covers the whole screen. Looks like an issue with an adjustment but could also be caused by bad parts on the chassis or a problem with the tube itself. Try adjusting the monitor first to see if you can get the colors balanced. See our post on Adjusting An Arcade Monitor for more information. You might also try touching up the solder on the input pins of the monitor chassis and checking the connection from the game board to the monitor as well. If you can’t adjust it out and the connections look good, you might try some of the procedures we discuss in our post on Checking A Monitor Tube. There’s also an outside chance that there’s an issue with the tube itself that might be solve by Using A Tube Rejuvenator so it’s worth taking a look at that video if the problem continues.

Hope that helps. Thank you for your question and good luck with your repair.