I just came across this information as I was trying to figure out how to deal with those irritating color splotches that appeared on my TV screen after leaving a non video rated speaker next to my TV.  As I was trying to look through eBay to find a degausser that would save me a few bucks over calling the TV repairman out or over taking it to a shop for a less than 5 minute repair, I discovered a neat website called "How things work" published by the University of Virginia.  I'm sorry, but it appears as if the draconian rules of eBay appear to prevent me from posting the actual web address.  However, using the above information, it should be simple to do a Google or Yahoo search for the site and arrive at the appropriate site, if you wish to review it for yourself.

The author there describes how today's CRT monitors generally have a degaussing feature built into the controls and that any televisions made in the United States for the last 20 - 30 years have an auto-degausser that activates when the set is powered down and then turned on again.  However, the power may have to be off for 15 minutes or so to allow for proper cooling, and consequently, proper degaussing to occur. 

I am sorry to spoil the party for the sellers in Hong Kong of the cheap Television Degausser that they are selling in mass quantity here, but they simply appear to not be necessary.   Chinese sets evidently are not made with this technology as of yet.  Besides, the reviews that I read by the buyers of these items appear to be mixed at best.