Convergence question
 

I've been playing with the convergence on my CT-100 again. I got it even better, after 30 minute warmup. Its really great except in one corner. Over much of the screen its almost perfect. In the bad corner its about two beam widths off.

So the question: How good can you get your 21 inch roundie, 21AXP22 to 21FJP22? I never saw any delta gun set with magnetic convergence as good as the best 15GP22s I've seen.

Are there diffferences between models in the best you can do. If so, what are the concensus best ones? Do you, like for the CT-100, have to adjust yoke tilt
or convergence yoke tilt to get best results?

The 21FJP22, rebuilt by Scotty, was the best converged of anything I have seen when I had it in my CTC-5. The GE branded rebuilt 21AXP22, however, is less than optimum for convergence and purity. I suspect the gun assembly may be rotated slightly, but can't prove it. It requires fiddling everything every which way to reach a compromise. Right now the top convergence is worst, and lower left has worst white screen purity, although red, green, and blue purity individually are OK.

GE "Good Enough"

I have seen a few 21" sets with perfect convergence. Miniman82 had a 1968 Philco roundy that had perfect convergence that I saw in person. My Conrac CYB21 roundy broadcast monitor (with a consumer grade RCA CRT) is pretty much perfect...I forget if my TM-21 is or not.
I need to run my roundys more and see what they all do some have been dormant over a year and I forget how good they were.

On the other hand my CT-100 is good and watchable, but not even close perfect. Both purity and convergence are somewhat of a compromise...but livable under normal viewing. There's a line of imperfect purity on the screen that I suspect is a defect in the shadow mask. I my Westinghouse H840CK15 needes me to fix/tune it up so I can see how well it works when dialed in.

15GP22 Defection angle H 45, V ?

21AXP22 Deflection angle H 70, V 55.

All things being equal, it would be more difficult to get perfect convergence from 3 beam 21 inch early color television 1954. I have never seen perfect convergence on a CRT.

It was easy to get perfect convergence on any digital CRT TV: just adjust the position of the pixels
of the three images (not beams!) before DAC. This applies to distortion also of course.

I've seen ultra high res three-tube projectors with perfect convergence. This requires
a stable mount and screen on the wall of course.

I’ve converged literally hundreds of 19, 21, 23 and 25” delta gun sets, new and aged while working at an independent shop and Magnavox dealer.

Close, yes. Some brands were better, some worse, some unbelievably bad.

Perfect convergence in terms of the entire viewing area doesn't exist.

The “perfect” convergence is in the eye of the viewer.

Go for the viewing area and the rest will be fine.

My 15G, at least before it lost vacuum, never got great purity or convergence. The red field had a tinge of blue at both sides, but not noticeable on normal programming, and edge convergence was not great either. The deflection yoke had to be mounted at a considerable angle to the CRT to get it even close to correct. The 15G convergence system did not have the individual adjustments of the later magnetic convergence tubes and was much more a compromise as a result.

I did get nearly perfect convergence on a few delta gun tubes; one 21" Quasar II in a metal cabinet and a 14" hybrid RCA portable. Most of the time you just had to get it as good as you could at the edges and just accept a bit of fringing.

The best converged CRT I ever experienced was a Sun Microsystems 21" monitor with a Sony Trinitron flat screen CRT. I know they must have had a ton of circuitry for adjusting the convergence in all areas of the CRT screen. There was virtually no interaction between the convergence controls. It was good all the way to the corners. Oh, and the user had access to all the convergence controls from the front panel.

That's your answer.

A three gun color CRT is really a marvel of its time, and it's crazy how good they actually were in mass production.

I remember a couple of picture tube jobs that really fought back when trying to converge. They were so easy to change, we would sometimes just return the tube to the local dealer as defective and the new one would line right up. Fortunately, that was a rare occurrence - maybe 10 in 30 plus years of doing quite a few of them.

Between a less than perfect shadow mask and a gun just slightly tweaked either globally in the neck or individually in the assy, you'd get one here and there that was obnoxious.

John