The imperfections in CRTs drive me crazy. All I see when I use my monitors are the flaws.

How close the yoke is to the screen, as well as the tilt, can effect the color in addition to the convergence rings.

https://youtu.be/Q2IHJfvD-70?t=309

Looking at your pictures, for a CGA monitor especially, it doesn't look that bad to me. You probably can do much more than open it up and play with the convergence rings some more.

mothergoose729 wrote on 2021-02-24, 18:47:

The imperfections in CRTs drive me crazy. All I see when I use my monitors are the flaws. […]
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The imperfections in CRTs drive me crazy. All I see when I use my monitors are the flaws.

How close the yoke is to the screen, as well as the tilt, can effect the color in addition to the convergence rings.

https://youtu.be/Q2IHJfvD-70?t=309

Looking at your pictures, for a CGA monitor especially, it doesn't look that bad to me. You probably can do much more than open it up and play with the convergence rings some more.

I've played with the yoke a bunch (loosening the screw and moving it around) but I can't seem to get it any better. I can't tell you how close or tilted it is, I don't know how you'd measure that.

Do you think this is more of yoke issue or a convergence ring issue (or both)?

If the color is uniform on the edges and the center than adjusting the yoke probably won't help. Try the convergence rings again.

I think I got it as good as it's going to get. The PCjr monitor isn't exactly high quality...

http://atariprotos.com/temp/fixed1.jpg
http://atariprotos.com/temp/fixed2.jpg
http://atariprotos.com/temp/fixed3.jpg

Isn't it also composite? You aren't getting the highest quality signal either.

mothergoose729 wrote on 2021-02-24, 21:28:

Isn't it also composite? You aren't getting the highest quality signal either.

It can do composite, but this is CGA. Someone else was telling me that the PCjr monitor has the lowest dot pitch of any CGA monitor of the time. This doesn't surprise me somehow.

I have done several convergence jobs on CRT and they are very interactive and depends on quality of CRT shadow mask and quality of curve inside of the CRT's face.

This is ONLY when you have to replace the deflection yoke!!

FIrst step: Slide N rotate the yoke to get center and horizontal and vertical line (center cross) in middle correct. There are 2 pairs of rings with tabs, this pair moves the whole red, other two rings moves all the blue Then nod the rim of the yoke to get most of the convergence close then back to the rings again and back to nodding the yoke then fix in with rubber glue and rubber wedges.
Then collect some chevron magnets, lay on the shoulder of the bell move around and turn the magnet around till one corner is good, stick it on. Repeat correcting outer convergence on rest of CRT face. Finish with flat flexible magnet wands slid under the yoke.

Yes complicated. I was doing this for a former repair shop that I worked at. My favorite is RCA's well done digital convergence design on rear projection TV, one step is about 1/2mm and does not distort as corrections builds up along the grids like other brands does, which I hate so much, and more coarse corrections which you have to work about 4 to 5 vertical and horizontal spots gradually otherwise the internal calculations grow more errors giving you with sine wave shape. JVC is good example of this.

Cheers,