This to me sounds just like a tube that has worked for many hours... I have seen the same in 1084 monitors that were left on on tv stations and similar environments.
I'm afraid there is nothing to do other than a tube swap - which means better search for another monitor...

CRTs have some nasty high voltages so whatever you do be careful in there.
If you don't know then look up how to discharge capacitors IN CRTs.

Yes, fresh capacitors might help.
I have not worked on a whole lot of CRTs and it's been a while but there are usually other adjustments inside.
If you can find one then you might be better off taking it to a TV repair shop.

The Service Manual can be found here.
https://www.manualslib.com/manual/1156759/Son … 0gs.html#manual
.

I dunno if he's still around but there was a gent over at badcaps.net that knows CRTs really well.
His handle was kc8adu.
That's where I'd go if I had CRT questions.
.

When focus is off and the focus pots don't do much you need to boost acceleration voltage ("screen" pot), if it just causes discoloration of the image the tube is worn out and there isn't anything more you can do.

CRTs are blurry from around 720p and up. When comparing to crisp LCDs that is. Also refresh rates beyond 60Hz or dark shapes (i.e. text) on light background makes it even blurrier. Also corners will be blurrier than the middle. Overall it should not be bothersome in 95% of games though. When was the last time you have seen a CRT? It is often the case people use LCDs for many years, then try CRT again and think it is worn out somehow - while it really isnt. Just some food for thought. I have CRTs with XXXX hours on them and they are mostly fine (when they work).

Try the OSD convergence settings again with my attachment if you did not use any good visual helpers. It is the Sony "Test Pattern" Program for CRT, version 1.20, 1998. Should work on both old and new Windows. Switch to "GRID" mode, place your eyes closely to the screen. Observe the white grid and go through each convergence setting one by one. Then repeat that several times until it is as good as it gets. After that you could try to adjust the HW knobs again with the "CHARACTER" mode. Then redo the convergence again, etc... And there is also the "FOCUS" mode with little graphics if you would prefer that one instead of grid lines and/or regular text.

I found a new CRT, which works much better! 800x600 is crisp and clear.

However, the issue became somewhat moot after I placed that CRT only on my 286-class machine... so it doesn't really matter any more. I have my other retro machines on a 1600x1200 LCD for the time being and that looks wonderful at native res or in DOS games (does a good job with them!).

Enjoy it my old cry was blurry, I used it for gaming and it gave it a native as effect without the actual performance hit as gives you