Purity problem in Panasonic TV

Hello I've got a Panasonic TV model TX-29AS10F chasis EURO-4H with a color purity problem at both sides of top of the picture. Top left has a greenish tint and top right is yellowish, the rest is correct including top middle. That discoloration gets worse as nearer to the edge. This model is 100Hz and has a completely flat CRT front.

In the user settings it has a geomagnetic correction menu that lets the user rotate the picture slightly, the curious thing is that adjusting that also moves that purity defect. The right one can be eliminated completely this way but then the left one expands even more. The opposite is also true but the left one can't be corrected completely.

I wonder if you belive it is more probably a CRT mask defect, a moved or misaligned yoke or some missing/fallen magnets. I don't see anything wrong apparently in the yoke but before I start playing with small magnets around the tube or moving the yoke I ask for previous experiences.

Thank you.

Reply to
Jeroni Paul
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Is the degaussing circuit working. IF you are not sure, get hold of a degausssing coil and manually degauss the CRT. You don't say if this is a new problem or was that waay from the beginning, and what might have happened such as dropping the set, or unplugging a vacuum cleaner right next to the set, or whatever. These are im[portant clues.

H. R. (Bob) Hofmann

Reply to
hrhofmann

hr(bob) snipped-for-privacy@att.net:

Thank you for replying. It appears to be working according to the noise it makes at startup.

I know, but unfortunately I don't have this info since it came from the scrap. A good starting point is that there was some evidence that it was neven been opened.

Reply to
Jeroni Paul

hr(bob) snipped-for-privacy@att.net:

Thank you for replying. It appears to be working according to the noise it makes at startup.

I know, but unfortunately I don't have this info since it came from the scrap. A good starting point is that there was some evidence that it's neven been opened.

Reply to
Jeroni Paul

hr(bob) snipped-for-privacy@att.net:

I have checked the degaussing coils operate correctly as playing with magnets I've magnetized the CRT and a cold degauss restored it. They also make a very audible noise.

Have been playing with some magnets around the tube and found that placing a small magnet at the right orientation around the deflection coils next to the tube gets rid of the purity problem. Two magnets, one per discoloration, I can get it perfect.

However I wonder if that is the solution to the problem or should I look elsewhere for something misaligned. The yoke appears firmly attached to the tube without signs of having moved, it is glued there. The convergence / purity rings are intact with their original painting as well as some adjustment screws around the coils.

I have noticed there are three windings electronically controlled, probably used for rotation. One next to the convergence / purity rings, one around the deflection coils next to the tube and one around the entire tube together with degaussing coils. What do these do? Could a failure of one of these cause the problem (I mean the electronics that control them)?

Reply to
Jeroni Paul

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