The auto degauss tries to remove any leftover magnetic field left on the CRT. If you want a more detailed technical understanding, you should do a google on CRT degauss, there is a little more to it, but that's the general idea.
The reason for multiple degauss is, well look at it this way. If your car windshield is really really dirty, just one pass with a sponge and squeegee is not going to get it all. you need to go over it a few more times to get it really clean. The degauss process is sort of like that, with a screen heavily magnetized.
Try it every few hours for a day, if that does not do it then you can call a repair shop and have them come out and do a professional degauss, which is more aggressive, I am guessing it will not be cost productive to have this done. It may indeed not even be the problem. Of course all of that is for you to decide.
Last edited by gary777; 06-30-2014 at 10:27 AM.