Color Purity Problems on a CRT

[Fudoh]

how much are those degausing wands ? Don't you think it would be worth trying one of those before writing the screen off ?

Something like that: https://www.youtube.com/watch?v=8cl8EpSAK44

[Josh128]

Ive done extensive testing and experimentation this weekend and Im reallly confident its not a magnetized shadow mask. The built in degausser actually does work, contrary to what I originally thought. When the set powers on, it looks great --everytime--until those same areas get some bright images for too long, then the purple/green blobs quickly begin to appear. Note, that even with a full white screen, it looks great for a few seconds (10 or so), then you can watch it change before your eyes. Even more telling, if you go back to dark scenery or black screen for a while, and you switch back to a bright screen, the discoloration is gone, but quickly begins to reappear. Its got to be mask "doming" from heating up with bright/white imagery. If it was a magnetized mask , the discoloration should be present always, and regardless of the brightness. Another tell is that when I tap on the screen, you can see the image slightly shake/shimmer in the affected areas.

Full disclosure, these images were taken with approximately 25ea 1cm x 1mm round neodymium magnets strategically placed with playdough (!) and duct tape on the back of the tube -- they oppose the blooming effect on low to medium brightness imagery-- but bright images will still become discolored, just not to the extent that they do without the magnets. Its a complete hack, and its still not enough to fully repair the issue. Ive opened a claim with FedEx and the seller with Wei-ya in hopes that at least one of them will come to the post and help. At this point, Im now thinking the mask came partially disattached due to rough handling.

[Josh128]

Made a YT video showing the behavior. Its a bit long, it would have been better to time-lapse it, but you can drag the video slider and get the same effect. Pay no mind to the black bars scrolling, thats just because my monitor frame rate is not exactly in sync with my cameras recording frame rate.


https://www.youtube.com/watch?v=5l7eEcJTqcc&t=6s

[Josh128]

Made two new short videos that are more interesting, attempted to use neodymium magnets to swipe erase / counteract the purity blooming on the M-3129. Shows how the problem is not magnetic, because the issue reappears as soon as the magnet passes, like water refilling a crevice.

Again, I believe this is because the magnet is moving the detached mask into place but as soon as the magnet leaves, the mask goes back to its original form. Still waiting on the seller / Wei-Ya , or Fed Ex to help resolve the issue.

https://www.youtube.com/watch?v=mETYh61QoYE

https://www.youtube.com/watch?v=AW8Yjk94El0

[Josh128]

...

[DJtheGamer]

I had a somewhat similar issue. Turned out that the grill wasn’t damaged, but the metal housing of
the monitor was magnetising? the tube. I stacked and taped a few two small neodymium magnets around the tube and the purity issues disappeared.

Before:



After:

[Josh128]

See three posts up. Couldnt cure it with magnets, it would help a bit but not enough. This one would partially "fix itself" simply by changing to a dark or black screen, then changing back to the bright would bring the issue right back within a minute or two--and the severity always depended on what was being displayed, with bright whites with contrasting blues or white backgrounds with black text being the worst.

[BazookaBen]

What's crazy is my new Sharp TV has this problem too. Not nearly as extreme as on my previous TV, but showing a bright color in one spot will give a "dirty screen" effect that's visible for a half minute afterwards in bright areas. Like you can spot it in some brighter levels in Super Mario World.

I wonder if this could also be an age related effect in the shadow mask or something. Like the chemical composition of the alloy has changed somewhat, become more easily misshapen or magnetized.

[Josh128]

What's crazy is my new Sharp TV has this problem too. Not nearly as extreme as on my previous TV, but showing a bright color in one spot will give a "dirty screen" effect that's visible for a half minute afterwards in bright areas. Like you can spot it in some brighter levels in Super Mario World.

I wonder if this could also be an age related effect in the shadow mask or something. Like the chemical composition of the alloy has changed somewhat, become more easily misshapen or magnetized.

The idea or possibility of a chemical change or oxidation is interesting, but a CRT is in effect similar to a very large vacuum tube, so theoretically there shouldnt be any air in it to allow for any oxidation. I think that partial detachment of the mask due to physical impacts would be more likely.

You said this set is new, as in new to you or new old stock? What year was it manufactured? My FD Trinitron Wega 27" was made in 2006 I believe, and I purchased it in 2014/2015 from an older couple that were original owners, so it hasnt been moved much, but we did have to wrestle it a bit to get to and in my house and its been moved several times since, but never dropped. Its got a really good picture, no purity problems to speak of, just your standard flat tube geometry issues and some "micro jitter"..

The seller here came through and refunded me for the Wei-ya/Makvision, and I ordered another one from Betson via freight, which should be in today or in the next couple of days. Im very interested to see how another, undamaged unit will perform, hopefully I will get to check it out in the next few days.

[BazookaBen]

This is a different set than the one I was talking about earlier in the thread. This one is a Sharp made in 2004. But it also a curved slot mask like the Panasonic I was talking about.earlier.

I guess it could have been dropped too, but it isn't really shimmering if I hit it either.

[Josh128]

I have a Wells Gardner K7000 curved tube in my Mace cab, and really, its got a fantastic picture other than some very light burn-in. The geometry is so good its essentially perfect and there is ZERO visible jitter, even with your eyeballs on the screen, unlike my Trinitron. Looking at a still picture on it is like looking at a painting. And its at least dated back to the mid to late 90's, so age doesnt seem to be a factor there.

[BazookaBen]

Another thing I'm wondering is if the original owner ran the screen too bright for too long, which maybe put heat stress on the shadow mask?

I'm just spitballing here, I don't really don't know.

[Josh128]

Got any pics?

[BazookaBen]

It's hard to capture in pictures because its subtle. But basically, if I show a bright white image on the right side of the screen, it will turn a little yellow/brown.

The only game I've noticed it in is Super Mario World because it has some levels where the backgrounds are pretty flat and bright. I'm just happy I can TATE this TV and its useable. I think I can fix the bad spot on the right with a magnet, or mitigate it anyway.