>Hi all
>
>Just curious. We have our TV under a reinforced concrete staircase. Yesterday evening the TV picture tube gathered some magnetic flux (green colored patches) towards the top of the picture tube. Most of the patches are now gone except one at the top left corner, hopefully it will go away too.
>
>What could be the reason? One thing I have in mind is that the concrete staircase has a lot of metal in it (for the last 23 years, staircase, the TV is new :)). Anything in the Earth's magnetic field affect the metal inside and thus the picture tube?

Unplug the TV for at least an hour, and then turn it on again. If this does not work, a cheap component called a PTC is most likely defect, and must be replaced.

This is a standard problem, and that's why all CRT TVs have a circuitry called degaussing.

When I was younger, I sometimes carried a magnet in my pocket, and when nobody watched the TV, I moved the magnet back and forth in front of the TV. Everybody thought the TV was defect, and expected a big repair bill. When I told them that they could turn the set of to cool down, and then turn it on again, they thought I was a genius.