Convergence Issue - Videokarma.org TV - Video

VA561 · #1 10-21-2021, 09:50 PM

Hello Everyone

I am trying to complete a convergence on my '56 RCA Wescott. I attempted to follow the setup procedure to get to this point. As you can see in the photo everything looks great except for the right edge. I don't understand it. Any ideas on how to proceed ?

Electronic M · #2 10-21-2021, 10:53 PM

Most of these sets you can't get completely perfect, and if you get perfect to the edge on one side will be unacceptable on the other. I'd try adjusting it so the misconvergence is symmetrical and improve it evenly as much as possible. If you can't get it good to within 2" of the edge all around check convergence components on the chassis.

old_tv_nut · #3 10-21-2021, 11:55 PM

Remember that the red and green move at 120 degree angles, so the so-called "vertical" and "horizontal" dynamic adjustments interact. "Vertical" and "horizontal" controls refer to what part of the screen is affected, not matching horizontal lines or vertical lines.

This result indicates that the vertical dynamic adjustments are wrong as well as the horizontal, in such a way to make the horizontal lines good while the vertical lines are way off. If only the "horizontal" adjustments were off, then both the vertical and horizontal lines at the right side would be mismatched. One of the red and green colors would be wrong northeast or southwest, and the other wrong northwest or southeast. (Don't ask me to remember which is which, find out by turning the static convergence.)

Do you know if the convergence coils are exactly over the internal pole pieces of the CRT? If not, you can get strange results as you try to get enough adjustment range. On the tube in my set you cannot see the pole pieces, and you need to look at the position of the convergence coils in the manual and then adjust them forward or back a little for maximum effect. Unfortunately, I haven't seen service info that actually gives measurements of the proper position.

By the way, don't bother to keep readjusting the static convergence every time you adjust dynamic. These sets do not have the diode clamps that later sets used to keep the center convergence constant. Instead, do the static center convergence first, then adjust the dynamics for equal errors from side to side (horizontal adjustments) and top to bottom (vertical adjustments) and finally readjust the static convergence. Then you can try a second finer tweak on the dynamics.

zeno · #4 10-22-2021, 04:07 PM

The right side is always the hardest, especially blue for
some reason. It looks good but IMHO should be better.
In the pix the purity looks a little off. You may want to go back
to the start & watch for any controls that are not doing much.
Also see if you can find the EXACT positioning of the neck components
the way RCA wants them.

73 Zeno

LFOD !

old_tv_nut · #5 10-22-2021, 09:03 PM

Just a wild thoguht - I notice the right side horizontal inearity is off. I wonder if that could be part of the problem?

old_coot88 · #6 10-23-2021, 12:14 AM

Anuther wild thought. Phil Nelson once had a convergence problem (on a CTC-11 IIRC) that turned out to be one of the wires going to one of the coils in the convergence yoke. It had broke off right at the solder joint. Can you check visually to see that they're all secure?

old_tv_nut · #7 10-23-2021, 07:00 PM

I want to correct what I wrote about the horizontal and vertical dynamic interaction. The picture you posted shows only a horizontal dynamic problem on the right side. What has happened is that both the red and green correction are either too strong or too weak there (probably too strong?).

One color has moved up to the left and the other up to the right (or down to the left and down to the right) so that the vertical displacements are equal (hence good horizontal lines). but because of the 120 degree offset, the horizontal displacements are opposite when the vertical offsets are the same. So the green is pushed toward the center while the red is pushed toward the right edge.

Sorry, I failed my engineer's spatial understanding test on this one!

reeferman · #8 10-24-2021, 01:07 AM

If that's a CTC-5 chassis, live with it.
They were a BEAR to converge 55 years ago, let alone 2021.
I too have found the RH side is the biggest culprit.
You might get it marginally better if you play with it enough.
Then again, it may get worse.
At their current age, delta gun sets will not get "perfect" convergence.
Watch the program, not the convergence.

old_tv_nut · #9 10-24-2021, 10:23 AM

Out of curiosity, I wonder what it looks like with the convergence yoke unplugged. Haven't tried that with mine, just tweaking you!
But my random thought is that if the right side looks better with no correction, it may be an indication that you've walked yourself into a corner and it's worth starting over from neutral.

Yamamaya42 · #10 10-24-2021, 10:53 AM

Quote:

Originally Posted by old_tv_nut

Out of curiosity, I wonder what it looks like with the convergence yoke unplugged. Haven't tried that with mine, just tweaking you!
But my random thought is that if the right side looks better with no correction, it may be an indication that you've walked yourself into a corner and it's worth starting over from neutral.

That may not work so well

At least with what I have seen with my CTC-16XL and the GE-CTC15 clone, if the convergence is unplugged it caused a partial loss of vertical height, and threw everything out of wack, not sure if THIS set is the same way however.

found this out by forgetting to plug the damn thing in a few times!

old_tv_nut · #11 10-24-2021, 12:16 PM

Quote:

Originally Posted by Yamamaya42

That may not work so well

At least with what I have seen with my CTC-16XL and the GE-CTC15 clone, if the convergence is unplugged it caused a partial loss of vertical height, and threw everything out of wack, not sure if THIS set is the same way however.

found this out by forgetting to plug the damn thing in a few times!

Oops - didn't think about the loading issue.
Well, I said it was a random thought.

Electronic M · #12 10-24-2021, 01:38 PM

Quote:

Originally Posted by Yamamaya42

That may not work so well

At least with what I have seen with my CTC-16XL and the GE-CTC15 clone, if the convergence is unplugged it caused a partial loss of vertical height, and threw everything out of wack, not sure if THIS set is the same way however.

found this out by forgetting to plug the damn thing in a few times!

The CTC-5 is different from the CTC16. The CTC-5 has all the convergence circuits built into the main chassis and only the convergence yoke unplugs.
The CTC16 has the yoke hard wired to the convergence board which unplugs from the main chassis....Also IIRC the CTC16 remotely mounts a lytic that's important to the vertical on the convergence board for some reason.

VA561 · #13 10-24-2021, 02:05 PM

I want to thank everyone for the helpful advice I received. The winner and undisputed heavyweight champion in this battle was the RCA Wescott. I tried for hours to adjust the convergence but with but with no success. I think Reeferman said it best; If that's a CTC-5 chassis, live with it.
They were a BEAR to converge 55 years ago, let alone 2021.
I too have found the RH side is the biggest culprit.
You might get it marginally better if you play with it enough.
Then again, it may get worse.
At their current age, delta gun sets will not get "perfect" convergence.
Watch the program, not the convergence. I should just be glad that at this point in time the set works! Its obviously not going to be a daily watcher. So on occasion I will sit in my recliner, cross my fingers and turn the set on. It is a piece of tv history that I am just trying to preserve. I have a friend who actually worked at the RCA plant when they were building these sets. He said to consider it a miracle that these old tvs still come to life when you turn the switch on. One thing I will do is to install a computer fan to try and keep the flyback cooler. The red fringing on the right will always bother me but sometimes it is best to compromise and be thankful that it actually works! Sorry if the pictures came out sideways. They were upright on the computer when I uploaded them.

zeno · #14 10-24-2021, 02:57 PM

As an aside many sets put the V out cathode electrolytic & a
parallel resistor on the CONV board. If you unplug it the V lin will pull
up. Also with no H&V pulses the L&R, T&B will be way off. The
center will stay good. When we jigged a chassis we had plugs that
would replace the V cap & resistor & give good V.
The rest didnt matter.

73 Zeno

LFOD !

Yamamaya42 · #15 10-24-2021, 03:42 PM

Quote:

Originally Posted by Electronic M

The CTC-5 is different from the CTC16. The CTC-5 has all the convergence circuits built into the main chassis and only the convergence yoke unplugs.
The CTC16 has the yoke hard wired to the convergence board which unplugs from the main chassis....Also IIRC the CTC16 remotely mounts a lytic that's important to the vertical on the convergence board for some reason.

the CTC-16/X and the GE-CTC-15 clone seem to be identical.

both having 2 windings off the Vert output feeding convergence.
https://i.imgur.com/cdZ4cg6.png

also both look the same,having 5 drop caps.
https://i.imgur.com/0H4QnUo.jpg
I can't explain why you lose sweep when you unplug it.
I just know that you do, for some weird reason :O