My girlfriend was rearranging her living room this morning when she noticed something very strange. She moved a stereo speaker from right next to her TV, where it has sat for some time. When she turned on the TV, the color on the side of the TV screen where the speaker used to be is now all shifted towards the green. When she moved the speaker back where it was before, the color returned to normal. Note that the color shift was confined to only the lower corner of the screen on the side where the stereo speaker has been sitting for a while.
I assumed it had something to do with the speaker’s magnetic field, since all speakers are driven by large magnets, but why would the TV only be affected when the speaker was removed? Will she have to leave the speaker next to the TV forever in order to get good color? Will the situation deteriorate over time? What the hell is going on here?
It is well known that TV screens are affected by magnetic fields, particularly from longterm exposure as you described. The set now needs to be “degaussed.” Most modern sets have an automatic degaussing circuit that does this every time you turn on the set. In olden days, you used to be able to buy a degaussing coil at places like Radio Shack. Just wave it over the front of the set until the color shifts go away. If you can’t find a degaussing coil, consult a TV repair shop.
Thnaks for the advice, Chas E., we’ll give the degaussing thing a shot. But I’m still confused as to the specifics of what’s going on. Why does the screen look fine in the presence of a magnetic field and change colors in the absence of same? I assume that something has been magetized, but what? Shouldn’t the distortion occur while the field is present as well as when it is absent? In fact, shouldn’t the distortion be less intense when the magnetic field is taken away?
Your TV has become magnetized from the speaker. Apparently, when you have the speaker next to it, the fields cancel out, leaving you with a good picture. If you move the speaker, the TVs field is all that’s left, and it distorts the picture. It almost sounds like you’ve degaussed the TV once with the speaker next to it, for the fields to cancel out so well.
In any case, you can have a TV repair guy degauss it for you. If you’re brave, it’s possible to take a small permanent magnet and degauss it yourself. Bring the magnet near the screen, and “wipe” it across the distorted area. Often you can “wipe” the distortion away (you’re actually demagnetizing the screen). WARNING- you can easily wind up with a much worse picture if you’re not careful!
Arjuna34
If you’re desperate, you can degauss a TV with a preheated electric iron. Just don’t get it too close, just wave it around the discolored screen area about a foot or so away, you’ll know you’re close enough when you see the screen get discolored a bit from the magnetic field the coils put out.
But as Arjuna says, be careful or you can screw things up worse.
As to why this effect occurs, well, I’m not too sure, but it appears that the metal frame around the picture tube picks up a magnetic field from the longterm exposure. Remember that the electron beam in the CRT is moved around with an electromagnetic field, all you have to do is put the SLIGHTEST stray field and the electrons don’t hit the right spots on the screen grid.