One of the great things about flat-panel displays is that they don't need purity or convergence adjustments. I'd like to tell you about two purity problems I've had with my own equipment (hmmm...) and get your views on the second.
Case 1: When I purchased a Toshiba CZ-3299K IDTV, the set arrived with a severe impurity splotch at the lower-right corner. This appeared to have been caused by a shock to the shadow mask during shipping. I put up with it, until I moved to a condo in 1998. Lo and behold, the splotch vanished! The "shaking about" during the move must have de-warped the shadow mask, or perhaps knocked it back into place.
Case 2: About five years ago, someone in this group had a question about removing impurities. In my desire to demonstrate that there was no degree of magnetization that could not be removed, * I held a bulk-tape eraser designed for metal-particle tape near the lower-right of my 400-series Sony WEGA IDTV, and shut it off. Naturally, the aperture grille was badly magnetized. Much to my dismay, I could not completely remove the impurity!
It persisted, in varying degrees, until yesterday. I had the Magnolia guys move the set into the bedroom -- and it was gone! (I should note that the set now sits at 90 degrees with respect to its initial position. But it's unlikely that the original impurity had anything to do with the Earth's field. There was no impurity before I'd "zapped" the set.)
Thoughts, anyone?
- This is at least theoretically true, as there is a limit to how much any magnetic substance can be magnetized, and it cannot be greater than the magnetizing force. (I think.) (Please note that I'm talking about magnets, not solenoids.)