Req: Help with a 19" TV purity problem

Tim wrote in news: snipped-for-privacy@news.aliant.net:

I assume that this is a CRT tv, not a LCD or plasma tv.

Sounds like the 'metal object' contains a strong magnet or has been magnetized. I have some magnets that will effect a CRT from over 2 feet away.

A transformer can also radiate a[n AC] magnetic field that disrupts nearby devices.

If you can find the source of the magnetic field and move THAT away from the TV, it should fix the problem.

It is possible that putting the set in place and then 'degaussing' everything in the vicinity will 'fix' the problem.

Does your Satellite receiver have a built in hard drive for recording programs? It is possible that the drive is 'leaking' a strong magnetic field [but most hard drives confine the field very well]

Yes the TV is CRT, and no, the receiver does not have a HD in it, nor does it have a large transformer. The purity problem is static, that is it does not change colour, so I don't think it's a transformer, as that would cause a rainbow effect.

Maybe I'll try rearranging the "stack" of components to see if one of the other devices cause less magnetic radiation, or reflection if that's the case.

It would be nice if this set had a manual degaussing option, but alas it doesn't. I don't even hear the coils buzz when the set comes on, but there are no other purity issues, so they must be functional. I'll take my tape eraser down with me, and try that to see if the problem returns after zapping the screen.

Thanks,

- Tim -

Tim wrote in news: snipped-for-privacy@news.aliant.net:

Lacking an eraser, if you can hang a magnet on a string so that you can spin it, you can sometime degauss with that.

I had a nice heavy magnet from an old radar magnetron that had a hole in just the right spot. I had a loop of copper wire threaded through the hole and hung the contraption from a piece of string. I would wind it up good and let it spin, slowly moving it away from the monitor. Did a good job of degaussing.

Sometimes, for a joke, I would spin it on the other side of a wall, near someones monitor. They would come running out of their office "something strange is happening to my monitor. The picture is wobbling all over the place and changing colors!" :)

oted text -

The OP did not say if the stand was metal or not. If it is metal, that may be adding to the problem. The spinning magnet to degauss is an old trick that works well as long as it is spinning rapidly compared to how fast you are moving awa from the set.

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The stand is wooden. The shelf is merely a 3/4" press board with=20 arborite on the top. The lower shelf has 3 devices stacked up on it,=20 with the satellite receiver on the top of the pile, and about 1" away=20 from the bottom of the shelf the tv sets on. The whole thing is only=20 about 21" wide and about 3 feet tall.

- Tim -

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try putting a sheild between, see what you can find, a sheet of alunimum might be enough. sheet of tin that is grounded might be even better. I have screwed up a couple of TV's by playing with magnets near them, never had much success with degaussing them that way but I am sure it is possible.

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In the past I have tried using Aluminum to shield against RF, but=20 haven't had much success with that. I will try a grounded sheet though,=20 maybe that will work better. The worse case is that it makes the problem=20 even worse, but it will go away the next start up.=20

- Tim -

philsvintageradios wrote in news:d0401b14- snipped-for-privacy@z24g2000prf.googlegroups.com:

Shielding against a DC magnetic field REQUIRES a ferris material. The stronger it is picked up by a magnet, the better.

Mu-metal is the best kind of shielding.

Aluminum, whether grounded or not, will have no effect. Neither will copper. You need something that will 'short out' and 'contain' the magnetic field.

On the other hand A conductor WILL give some shielding for AC magnetic fields. The degree of shielding depends on the frequency of the AC. The higher the frequency, the easier it is to shield against an AC field with a GOOD conductor of any kind.