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OK, this is a problem with a 19" Citizen TV. It is just over a year old.
If the set is put on a stand that has a metal object (like a Satellite Receiver on a shelf) mounted within 8 inches below the set, the pic has a very noticeable purity problem all the way across the bottom and about
1/2 way up each side. If I raise the set up, the purity problem will diminish, but even up at 8" away from the console stand, it still has slight purity issues.
Raising the set up on boxes is problematic, as the space is very limited. I would like to shield whatever it is. I am not sure if it is a reflection from the set or radiated magnetic fields from the equipment below.
The console is in a travel trailer, so I cannot move everything away from the tv, as most of the electronics are in this one console, with the TV on top of it.
Any helpful suggestions are appreciated.
Thanks,
- Tim -
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OK, I thought I would post the solution to the purity problem I had in the posting quoted above.
I decided to try moving the CRT set around to see if the effect was environmental. It did indeed seem to effect the purity.
I noticed that even a set magnetic clasps located about 2.5 feet away had an effect. I tried removing the clasps, but the end result was minimal.
I tried rearranging and the items located beneath the TV. This resulted in a significant reduction with the purity issue.
I then removed everything from the shelf under the set. Most of the problem disappeared, but about 1/4 inch along the bottom still showed the problem.
I decided to take the set apart, as I never heard the degaussing coils hit when I turned the set on, I thought they may be disconnected. I found out that they were connected, but only fired when the set was first plugged in and cold. They do not hit every time the set is powered up. Regardless, the purity problem remained.
I then noticed something strange. The metal strap that the CRT is mounted in had the usual steel wire going across the bell of the CRT and it that was grounded the set, but it was only contacting the steel frame at 2 small points, where spring was clipped, and a single wrap around the steel frame. I attached a copper wire to one of the mounting screws for a really good contact, and wrapped the other around the steel wire were it was crimped to the ground wire.
When I fired up the set, the purity problem was gone completely. Even replacing all the hardware on the shelf and the magnetic clasps would not cause any problems. I found that the set was now almost immune to magnetic inteference, even from a magntic screwdiver moved across the face of the CRT. When I got anything magnetic close to it before, it would severely effect the purity.
The problem has never returned since.
I hope this help someone in the future....
- Tim -