Very persistent and hard to fix (maybe impossible?) Purity issue

[tongshadow]

I'm having serious purity issues on this set and I wanna know if any of you, which seem to be very experienced in the matter, have encountered something similar. Compared to most common purity issues it's somewhat subtle but noticeable in person. What happens is that the area around the center of the display is having purity issues, as it can be seen in this picture:
https://i.imgur.com/fa3FsGr.jpeg

Instead of a solid magenta color, Im setting blueish tones around. Same for a white screen but it's greenish/yellowish. Here's a list of things I've tried:

• Moving the yoke forward/backwards
• Replacing the yoke with an identical one
• Adjusting the purity rings only makes overall purity worse
• Degaussing wand
• Can confirm the degaussing circuit is working
• Removing the purity magnets dont affect the screen at all

Im pretty experienced when it comes to yoke adjustments but this is the first time I'm seeing something like this, it's like something around the tube is magnetized. The set is rather old (20+ years) and very used, but otherwise the picture is nice despite the purity issue.

 

[Mukuro_W]

May I know wich monitor set is it? If you have already checked the PTC and if you have already tried to manually degauss with a degaussing coil, and the issue istill there, most likely the shadow mask is dislodged due to an impact and you can only try to cure with magnet disks but the result will be not perfect all the way ..

 

[tongshadow]

It's a TV that uses an A68QCU259X tube. But would a dislodged shadow mask cause a purity-like defect? I thought the effect would be crazy colors all over the screen. The case is perfect, no cracks or broken plastic, so I dont think it was dropped at some point.
Also, I tried changing the convergence/purity rings set but the issue still persisted.

 

[Metal Slug]

Try placing a magnet on the metal strap around the outside of the tube? Sometimes all it takes is a small Neodymium magnet to fix stubborn purity. (What side is placed up/down will make a difference.)

 

[Mukuro_W]

To correct the purity error on peripheral areas, disk magnet s on the four corners near the yoke could be used, also try to move the set in other position and O room if the discolorstion is always in the same spot you got a tube damaged even if there is not even a scratch.

 

[tongshadow]

Try placing a magnet on the metal strap around the outside of the tube? Sometimes all it takes is a small Neodymium magnet to fix stubborn purity. (What side is placed up/down will make a difference.)

Would a speaker work? I dont have a neodymium magnet. Also, how about using the degaussing wand at the back of the tube? I heard it can demagnetize the rings permanently.

To correct the purity error on peripheral areas, disk magnet s on the four corners near the yoke could be used, also try to move the set in other position and O room if the discolorstion is always in the same spot you got a tube damaged even if there is not even a scratch.

Im only getting the discoloration on the red colors (red, yellow and magenta), it's not noticeble on the other colors.
https://i.imgur.com/NU5Fs6T.jpeg

 

[Metal Slug]

Would a speaker work? I dont have a neodymium magnet. Also, how about using the degaussing wand at the back of the tube? I heard it can demagnetize the rings permanently.

Im only getting the discoloration on the red colors (red, yellow and magenta), it's not noticeble on the other colors.
https://i.imgur.com/NU5Fs6T.jpeg

Just go to Home depot and buy a pack of magnets, I think they cost $4. A speaker magnet is probably far stronger then what you need, and you can only use one side. Do not use a degausing wand at the back of the tube.

I think you will be surprised what difference a small magnet placed on the outside of the tube on the outside band can do. Move it around find the sweet spot where the colors look good and leave it there, sometimes it needs to be taped in place if it is not on metal.

 

[Mukuro_W]

The degaussing wand only on front of the tube, pay attention to the yoke position, check if this one is well seated against the tube.

 

[stj]

are any speakers, flourescent chokes, led drivers or magnetised metal objects near the monitor tube??

 

[tongshadow]

Just go to Home depot and buy a pack of magnets, I think they cost $4. A speaker magnet is probably far stronger then what you need, and you can only use one side. Do not use a degausing wand at the back of the tube.

I think you will be surprised what difference a small magnet placed on the outside of the tube on the outside band can do. Move it around find the sweet spot where the colors look good and leave it there, sometimes it needs to be taped in place if it is not on metal.

Tried some magnets on the outside of the tube, but it only makes the magenta turn into green splotches.

The degaussing wand only on front of the tube, pay attention to the yoke position, check if this one is well seated against the tube.

If I get the yoke too close to the tube I get the typical color patches on the 4 corners. Even in the ideal position the discoloration remains... in fact, it was glued pretty well from the factory but still had the discoloration.

are any speakers, flourescent chokes, led drivers or magnetised metal objects near the monitor tube??

Absolutely nothing, even removed the big ass speakers it has to no effect.

Question, does the position of the ring assembly matters? I havent tried moving it forward or backward like the yoke. Does it matter?