If the convergence is so good overall except in that one spot don't touch the magnetic ring assembly - you'll likely make it worse if you do. Small errors in the corners like that are corrected with permalloy strips glued to the glass bell, these are added at the factory (or by a service technician) and it's possible that one of them might have had its glue decay and fallen off over the years (I've seen it happen). Inspect the tube for signs of something that used to be there but now isn't, like spots with less dust than their surroundings, could be a permalloy strip, a small magnet or even a yoke wedge - whatever it is, if you find it somewhere on the insides you can reattach it and fix your problem. If that's not the case, you can add a permalloy strip to fix it as well. You can even make some out of x-acto blades, cardboard and scotch tape. 😉

Well at least you don't have my problem:

It goes away more the longer the monitor is on, but never quite completely and it always comes back as bad as that after it's been off for a while.

gotcha, i will search for that permalloy thing strip tomorrow when i open the case and when i have a lot of sunlight

your monitor is the same as mine, but i got the 15inch model. to be honest the 15inch for DOS is great, i really like the size besides during DOS age we all had 15inch and 14inch. My issue is visible when letters are shown, or in windows, but for gaming its fine, you actually dont see the problem like playing doom or other games. It is kind of bad that SONY is a well known brand and we end up having defects like these, i had sony TVs and never had a problem.

is this fixable??

Could be, but it's nearly impossible to have ideal convergence on the edges of CRT. Tweaking will make it appear somewhere else.

i took a flashlight and tried too look inside the holes of the case because i did not want to open it .too late here.

i saw no.stripes inside...i did see a small squared orange , the size of a stamp. and on top of that square there was a circle of.the size of a penny that looks like a magnet

saw one of those orange things in one corner and on the other opposite side corner there is one also

could that be the same as a stripe? ill have to open it tomorrow

Those are magnets used to improve purity mainly (i.e a pure color is that and tinted with another) but they will have effect on convergence too (alignment of individual colors). You could try move an existing one or add in another, in any case it'll be lot of trial and error with positioning aswell as rotation.
To correct such an error you normally slide a small magnet on a plastic strip right under the deflection coils. Some monitors have several of those, some none at all. Enter "convergence strip" into google image search to know what I mean. By careful positioning of those you can achieve perfect convergence and if you're lucky, perfect purity too but be prepared to waste a day or more on this 🤣.

convergence strips are very hard to find, i remeber searching for those and are not sold, not even found on ebay.
i saw someone doing a batch at a jamma forum, they are made of Mu-Metal (Ultraperm 80) and plastic strips and some kind of tape.

good luck with that

i opened the crt today

boy it was all black inside even those strips are black too because of the dust. there are 4 strips each pointing to each corner
the strips are glued with some kind of silicon glue. and next to the strip there is the orange square with the circle that i think its a small magnet.

i did not notice anything wrong, seems like the strips never moved, maybe this monitor was released like that from factory?

since i was opening something with high voltage i just did not touch anything.

Im not sure WHAT i don´t have to touch to get harm from high voltage. I saw some videos of people touching the strips and even the gears whilt the tv is on... i just don´t get What i dont have to touch and avoid.

Pabloz wrote:

i opened the crt today […]
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i opened the crt today

boy it was all black inside even those strips are black too because of the dust. there are 4 strips each pointing to each corner
the strips are glued with some kind of silicon glue. and next to the strip there is the orange square with the circle that i think its a small magnet.

i did not notice anything wrong, seems like the strips never moved, maybe this monitor was released like that from factory?

since i was opening something with high voltage i just did not touch anything.

Im not sure WHAT i don´t have to touch to get harm from high voltage. I saw some videos of people touching the strips and even the gears whilt the tv is on... i just don´t get What i dont have to touch and avoid.

If you don't know what not to touch, close it back up and leave it alone.

I'm pretty comfortable around everything inside of a computer, including a power supply, but I have never opened a CRT because I simply don't have the experience OR anyone to show me (IN PERSON) what I should or shouldn't do.

Looking up how to fix things on YouTube is great, but I'd highly recommend seeking help from someone in person when working on things that can instantaneously kill you if you do something wrong.