Geoff,

Looks like you are having some discoloration issues with your monitor. This can be caused by a couple of issues. We recommend starting off this repair by making sure that the degaussing coil (black, cord looking thing) that goes around the monitor tube is hooked up. There’s usually a 2 prong connector where it plugs in on your monitor chassis. Make sure that it’s hooked up and that it is properly secured around your monitor tube. If the built in degaussing coil for the monitor is positioned and hooked up properly then you might try using an external degaussing coil like we show in our post on Using A Degaussing Coil to see if it helps the issue. Also, rotating your arcade game can sometimes help the issue as well. We have had problems in the past with rebar causing this type of discoloration. While it might be a long shot it’s definitely worth a try.

With the above being said, it could very well be some impurities in your tube that are causing this issue. If this is the case, you might need to replace your tube altogether in order to solve the issue. There is a great article on 8liners at https://web.archive.org/web/20080705201439/http://www.8liners.com/datatech/monitor.html that talks about how to get the ohm readings off of your tube so you can find a comparable one. Remember that a television tube should work fine provided it has the same readings. There’s also a list of which television tubes are compatible with each arcade monitor chassis that can be found here: http://junknet.net/donor-tvs. With tube televisions selling for cheap at flea markets and pawn shops, it might be the way to go if you’re looking for a replacement tube.

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