Rainbow on Panasonic TV

I'd still approach it as a degaussing problem. Did somebody hold a strong magnet up to the screen?

sounds like a little AC 50/60 Hz getting in the supply system somewhere?

Maybe the heater on the Tube has shorted to the system ? or bad cap in the system? etc.. Just a guess..

Either that, some one has a magnet or something like it near it.

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No, it wasn't external magnets, speakers or other outside magnetic source. (no kids in house or others that may have accidentally done something) It could be some internal failure such as tube heater, caps, or stray AC. I prefer to save those type things for last.

Could there be a flaw in the degauss circuit? It looks too organized too be the typical magnetic problem. Round circular color bands in blue,red and green centered on the screen do not appear like other screens I've seen where kids were involved with magnets or nearby speakers.

Perhaps I can post a picture of what I'm seeing. I'll try and get a decent image up this weekend. Check later.

All opinions are useful to me, I'll want to consider everything before I eventually open this back breaker up. Thanks, Denis

It's not stray magnetic fields or the tube heater (that probably runs from the flyback).

And I assume it didn't fall on its face - which could distort the shadow mask to produce a similar result.

But you said the picture looked stretched at the corners?

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Sam G. said: "And I assume it didn't fall on its face - which could distort the shadow mask to produce a similar result. But you said the picture looked stretched at the corners"?

Sam, thanks for your response... No the set did not fall or suffer any kind of physical damage that would have damaged the mask. I don't have a color bar generator handy, but I noticed that programming that should have vivid color looks as if the color adjustment was turned down, sometimes as if it were a B&W show. But if you ignore the colors, the picture is still sharp. In fact my buddy joked the set is fine for a color- blind person.

The picture is not stretched but is pulled in a little at the corners. Not much though. It varies from channel to channel. It reminds me of what happens during a power brown-out. It's a minor observation compared to the circular rainbow problem. If I can get good representative photos, I'll post them on my personal site for easy viewing. Thanks Denis

Always degauss anyway.

Years back I went on a service call. The problem was a complete and utter mystery to me; the colors were random and rainbow-like all over the screen, but the purity was PERFECT. Gray scale was PERFECT. Red purity was perfect, as was green purity and blue purity. At this particular shop the rule was to call the head tech before giving up, so I called and the tech told me to degauss.

It fixed the problem.

THEN it occurred to me that there was a thunderstorm the previous day, and this customer was in the area that got hit hard. I asked her if she had experienced anything out of the ordinary and she told me that they took a lightning strike directly into the asphalt-paved lot next door. I still have no idea how the purity could be so perfect while the shadow mask was magnetized.

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distar97 wrote in news:1184359891.280300.267520 @w3g2000hsg.googlegroups.com:

Check the magnetic field coil correction system, Larger sets greater than anout 32" usually have a coil on the inside, fed with a modified pulse with some dc to correct for the earth's magnetic field.

If the circuit has failed there may be too much dc on this coil...

Simply unplug the coil and demagnitise the CRT. If that corrects the problem you know for shure where to look. This is not the degaussing coil it is smaller and closer to the yoke (deflection coils).

R!!

The screen may be magnetized. The internal degausser may not be working.

If the fault is not the internal degalusser, it is possible that the shadow mask in the tube has become defective.

Both of these types of faults are comon.

Jerry G. ======

Could that have been preexisting condition that you just noticed?

In any case, as others have suggested, try degaussing the set before digging deeper.

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Just take a strong magnet and wave it around the face of the tube moving back gradually. See what that does.

H. R. (Bob) Hofmann

Thanks to all for the advise. Good response. I'll check it out. In the meantime I took some pictures. You can see them on a page I set up off-board Go to: distar97 daht googlepages daht kom sellash tvrainbow (I hate robots, sorry) Note: do not include www

Thanks to all

that is excellent advice from AJ, Don't rule out the possibility of a degauss problem. You will need to open 'er up and check the degauss cct so as to be able to eliminate this as the most likelly cause.

-b.