Without much more detail I'd say there's a problem with the monitor chassis. Whatever makes the neck glow is not making the neck glow, so you can stop searching at the game board. I have a monitor that I yanked from an Outrun that currently does not work, it is a Sampo KGR-1901H. Bob Roberts sells a cap kit. If you want to make a positive ID, Bob also has pictures of just about any monitor that it COULD be. On mine it was on the side of the bracket, the only way to see was to remove the monitor. If it is a Sampo, there's not much you can do with it. Bob Roberts sells a cap kit, and the manual is available over at the arcade archive. If the flyback is toast, you're pretty much SOL.
Also make sure you read up on your monitor safety. Discharge the tube and the caps before you do work on it. The frame has some handles built in so you can at least grab it out without discharging it, just be careful. Chances are you'll yank it to find that the fuse on the chassis board has blown, meaning that something has shorted. The Sampo I have will by my first attempt at a cap kit, hopefully that does the trick.