another convergence question
 

ok so lets say your are done and have an ok convergence, if you were to remove the convergence coils from the neck (leaving the board plugged in) would it make since that the static convergence be ok or completely out of whack (as it was on mine). As i refine my technique I rely less on the 'this pot or coil does this approach" and rather focus on just trying to get the cross hatch as straight as possible. When done that way it seems to drop into convergence better than endless twiddling while focusing on just the area assigned to that control. I know that is not how its shown to be done, but I know that I ofter have less that perfect convergence that defies any amount of adj, like the entire line is tilted.

I often wonder if you should start by centering all the pots and center the slugs (1/2 in the coil) before touching the static, then start the process.

example if you have one pot cranked over and since it effects the static, then adj the static will only result in less than optimum adj range (if possilble at) for convergence of dynamic.

Trust me when I tell you: just follow the damn instructions! I twiddled with convergence a million times on the CTC-4, trying this way and that attempting to get it right. It's just not gonna happen. The instructions were written for a reason, I'm humbled to say that I am not smarter than the RCA techs who designed my sets.

:eek:Nay, nein, nix. Leave 'em where they were as the starting point.

Convergence adjustment is an iterative process. ALL the adjustments interact to some degree. Do static, then dynamic, then retouch static, and retouch dynamic. You will converge on the final solution (no pun intended).

I guess what I am getting at is did the factory start out with everything centered up (I would assume so), or how about the sets that jr, got his hands on and set evethhing at max CW. :D

It should not matter the starting conditions. If the procedure does not call out a starting position for the dynamic adjustments, It may require more than 2 iterations to end up at the final solution.

Wherever the controls were set from the last time at least gives you some sort of baseline. If everything was "ideal" at the factory and everything aligned the same then I'm sure that there would have been some preset conditions. And this is only good if everything is working right.
Change out the CRT and everything starts over again! Lots of varibles!!

I found out by complete accident that my CTC-11 is very watchable without the dynamic convergence board plugged in. Looks just as good as the Sylvania test jig CRT. I did however still have the dummy load plugged into the CTC-11 convergence board socket :D

My 4 is a PIA to converge. I wound up rotating the convergence yoke slightly to achieve reasonable results, but it sure ain't perfect, nor will it be.

Gee, I just replaced the CRT in my CTC-9A. Look what I have to look forward to :tears:

Same exact thing here! Is it rotated slightly anti-clockwise as viewed when looking at it through the top from the front of the set?

[QUOTE=kvflyer;3008771]Gee, I just replaced the CRT in my CTC-9A. Look what I have to look forward to :tears:[/QUOTE

Might not be too bad, as by the time the 7's were released they had the convergence problem under control, sort of. I was able to achieve perfect convergence in one of my 7s, but spent about 6 hours on the task. The settings held for a very long time, and the pic was great with a RE21FBP22 Sylvania tube, all new, not re-built. It was a Sanford in mahogany. Before that, RCA used carbon pots in the convergence circuits. In the 7, and subsequent chassis, they used wire wound pots, and improved circuits. It worked, for the most part, at least...
Aren't these damn TVs fun to play with and restore!? :yes:

Yes, exactly. My tube is what I believe to be an early tube with a "greenish" screen, not "silvery-grayish" as has been discussed before. Maybe the gun assemblies in some tubes are "off" a bit. Not really a problem here, as the amazing color reproduction makes up for minor convergence trouble.
I'm going to again go through the entire set soon, and will post any strange or appropriate findings.
Kevin

I have found very few sets that have perfect convergence, I agree with John Folsom that there is always some type of interaction between adjustments, always remember to let the set warm up for a while before adjusting the convergence. I agree that if you follow the recommended proceedure you will end up with a reasonable result.

Last time I did a convergence was in about 1979. It was on a Heathkit color TV. So, I am sure that when I get the CTC-9A going, it will be just like starting from scratch. Thanks for the helpful hints in this thread.

I will have more to offer on this subject in about a week. I am in the final stages of completing the restoration of the Hallicrafters CTC4 clone.. On my first attempt to get it up and running, the convergence was so far off I couldn't do anything with it. I discovered that almost all the pots on the convergence board were way off on value. After about a month of scouring the country for parts, I have completely rebuilt the convergence board with all new pots.

I would suspect that if you cant get good dynamic convergence on a ctc4 you may want to check the values of EVERY pot on the convergence panel. Especially the dual concentric 100 ohm pots that stick out the side. These 100 ohm pots are all carbon comp and it is my impression that they were not very durable. I have now built a personal stock of 100 ohm dual concentric pots that are all wire wound. I have no idea why RCA used carbon comp in this application. Wire wound would have been a much better option.

IN the past I have found the following to be helpful in addition to what has already been said about convergence. First of all if you are doing a convergence on a newly replaced crt, make sure you have the convergence yoke in the correct position followed by the purity ring and the blue lateral magnet.

The next step is to make your purity adjustments to get good pure scren colors. If you have the static red, blue and green magnets on the convergence yoke way out purity will not be correctly achieved. So what I do is put a patern generator using cross hatch and make sure the three color images are super imposed in the center of the screen first. Then I pull all the magnets on the purity ring at the front of the crt all the way out. At that point I disable the blue and green guns and go for the best red purity I can achieve following the purity directions in the Sams instructions. AFter red purity is good, I check blue and green for any impurity and touch things up using the pruity magnets at the front of the crt.

AFter purity is as good as I can get it, I set the cross hatch patern so that the center of the screen is misconverged by about 1/16 inch by turning the static magnets on the convergence yoke so I can see each color line individually. At this point I start to use the dynamic convergence board controlls to attempt to make the lines all parallel and equidistant from each other. When I have the lines as good as I can get them, I go back to the convergence yoke and reconverge the center of the screen using the static convergence magnets and the blue lateral.

And as was said before, convergence is a repetative process that gets better on each successive pass.

On later sets (post CTC-5) the circuits were designed so that the dynamic would not upset the static too much. However, on the CTC-5 and earlier, if you read the instructions, they say do the dynamic first for parallel lines, then do the static, then iterate.

I also noted on mine that a little fine rotation of the convergence yoke plus sliding back and forward to find the position of maximum effect was helpful.

Don't know what they did on particular sets. I do know that much later factory procedures would often involve first setting control slugs to a nominal mechanical position. So I would assume that any set you got is close to correct unless someone just went in and "tightened" all those "screws."

If you look back at my experience with replacing a broken blue H dynamic slug, you will see that I really had to try the full range (which I was afraid to do at first). But if you receive it unbroken, I'd assume it's close to start.

Edit: the nominal factory mechanical starting position might very well NOT be centered - so if the service literature doesn't tell you, don't assume.
2nd Edit - on the CTC-5, the pots are tapped at 25% rotation, and that (or very close) turned out to be the correct setting for the 21FBP22 substitute tube. It could depend on how close the guns are aimed for center convergence without any DC.