CTC-7: Convergence, Convergence, Convergence

[blue_lateral]

Originally Posted by jbeary

6K on the lateral magnet band??? YOWAZA! I hope that I don't lose that ground. I better check the solder joint on that thing because when this sucker shocks you, it does it real good.

Naw, 6k on the pole piece inside the tube. It shouldnt arc out because of the vacuum and the glass. The lateral itself is usually grounded.

John

[blue_lateral]

All right, now to set it up. You probably want to get set up to bias off the grids. Your dotbar generator probably has this built in. You can build a llttle adapter if it doesnt. I mention this, because you need to keep checking the purity as you go through the procedure. Having to reset the screen controls every time gets old in a hurry. To set up a set that is way out of whack you will probably be going through the whole routine at least twice (maybe more) if you want it perfect.

Purity comes first. Put the set in the position it the room that its going to be. You can have it scooted out from the wall, but it's relationship to North/South must be the same as it's going to be in the room.

Degauss the set thouroughly with a degaussing coil. With the coil parallel to the screen, make big round sweeping motions as you slowly back up from the set. Get quite a way away, turn the coil 90 degrees to the screen, and unplug the coil.

Now to set the purity. You dont want the brightness and contrast turned way up because things get blurry. Make the screen all red. If your dotbar generator wont make a white screen, You can unplug the tuner link to get a white screen with no snow. Kill the blue and green guns with the gun killers on your dotbar generator, or turn the screen controls down. Slide the deflection yoke back against the convergence yoke. Adjust the purity rings to make a big red ball. Moving both rings has an effect, moving one ring in relation th the other has another effect. When you have a big red ball, move the deflection yoke forward until the red fills the screen.

You will want to switch to a crosshatch now to see if the picture is level before clamping the deflection yoke down. You might find it easier if you turn all the guns back on.

Now check purity again. Turn the guns on one at a time and check red, green, and blue. I think 7's had some hairpin magnets around the outside of the tube to assist you in sorting this out. Make minor adjustments if necessary. Dont touch the rings (or the hairpins) after this. Purity affects everything else. If the rings move after this, start over from the beginning.

Switch to dots and set the static convergence (with the magnets) at the center of the screen. at least get it close. use the one dot setting if you have it.

Adjust the focus for the sharpest dots. You are adjusting for side to side as well as up and down. go for the best compromise. There will be a black dot just to the right of the white dot. Ignore that.

Now would be a good time to check and adjust the vertical linearity and height. There is no width adjustment on most roundies, so the yoke as you move it forward affects width, but you really need that adjustment to get the purity right. Make some nice square squares or rectangular rectangles or whatever your generator generates. Check the horizontal centering, too. The setting on the generator with one vertical and one horizontal line works good for this. You probably dont want any more (vertical) overscan than necessary to make it so you cant see dark at the bottom and the top. This usually all falls in to place, but if you put the yoke too far forward in the purity step the whole picture might be too big for the screen.

Check the static convergence again. Make them land on top of each other. Try to look at the whole color dot rather than the little screen color dots. SInce the little dots are arranged in triangles, there will always be red dots at one edge, blue at one edge, etc. Ignore that and watch the whole dot move as you move the magnets.

When you have good linearity over the whole screen, and good dot convergence at the center you can go on to dynamic convergence with the panel. You do need the instructions for that part, because the adjustments do refer to specific places on the screen. When you get it close, check center convergence again, and purity. You can adjust the center convergence and then go right back to dynamic convergence. If the purity needs fixing, go all the way back to the beginning. It gets closer every time you go through.

Post those pictures. What CRT do you have? I have a gun out of of a 21fb/21fj I could photograph or measure if it would help. If you have a 21cy I think this is still the right gun. 21ax maybe, but I'm not sure.

Good luck

John

[wcarroll]

Hey Jeff, Let me know if you can use an extra set of eyes and hands. This stuff is a mystery to me, but I'd be glad to lend a hand anytime.

Wes

[oldtvman]

keep in mind that any imperfections you see up close may not be visible at a normal viewing range. those systems were always suseptable to thermal changes, be sure and let the set warm up about 20 minutes before attempting any convergence alignment

[jbeary]

Wesley,

Yo man! I see your brother more than I see you, what's up with that? You need to let him move in with ya'll so when we see him, we see you too! Are you sure you want to get into this convergence stuff? You know how I am, I want it perfect! Com'on over anytime and get shocked some... What do you have again? A CTC-9? This is going to be the fun part after you get everything squared away in the circuitry of that set

I've got an oscilloscope and a dot generator for you if you don't already have either! Let me know if you've had the chance to work on that Silvertone...

John: Your set of instructions are dead on and this is pretty much what I'm doing except I'm not turning my blue and green screens down when I do the purity adjustment. I just kill the guns and then check the blue and green separately after the red is set. Thankfully, I haven't had to fiddle with the edge magnets. I need to remember to check the purity again after doing the static convergence because I think it gets thrown off as soon as I adjust any of the static convergence magnets. The wife came down with a bad cold, so I have to wait until I have the chance to take and post some snap shots. But thanks for letting me know that you have a set of guns we can look at. My CRT (or kinescope) is a 21cyp22... Pretty sure that's the number, but I don't have that info in front of me.

THANKS AGAIN!
Jeff

[wcarroll]

Jeff,

I still didn't get to the Silvertone set yet. I did want to start with a b&w set before starting on the CTC-11 since I'm sure the color set will be quite challenging for me. Instead of the Silvertone, I decided to rebuild the Predicta that we've had around here forever. That thing is a real pain to work on. But, I've been getting lots of good help from the forum members here. Perhaps the Silvertone would have been a better choice to start with?

Also rebuilt my McIntosh MX110 and am finishing up the restoration of my MC240 amp. Can't wait to give it a listen...

I'll send you a private message or an email so we can plan to get together soon. Sounds like the purity and convergence is a bit of following the procedure combined with a lot of art and some luck too!

Wes

[old_tv_nut]

hmmm.. that comment on the earlier sets with edge magnets makes me want to ask -- does the CTC-7 have an automatic degausser?

[blue_lateral]

I dont think so. That started with the ctc16 as far as I know. The voltage doubler power supply went away at the same time.

[vintagecollect]

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