Ctc-7aa

[DaveWM]

Nice, yes a starndard purity setup will prob take care of the colors, and make them pop even better.

[Electronic M]

A tape head degausser will do more harm than good.
You could probably scrounge a degaussing coil from a newish CRT type junk set and use that with a variac to degauss the screen.
I got my degaussing coil from an active TV repair shop, and you may be able to do the same. Ebay may also have degaussing coils....

Just throwing some ideas out there...

[IsthmusTV]

Thanks for the tips and kudos. I think I may be able to borrow a degaussing coil from a friend next week, so I'm not going to try anything foolish in the mean time. Right now, I'm just happy knowing that all the vital organs (including the oozing power transformer) are good. I've never done purity and convergence before so this will be a real learning experience for me. I'm glad to know that all you experts are out there when I need advice

The picture just keeps getting better. I adjusted the AGC which really woke up the contrast.

Now, I'm going to take a break and watch the Badgers in the Rose Bowl...

[Electronic M]

"Now, I'm going to take a break and watch the Badgers in the Rose Bowl... "
I can relate to that...just got a my CTC4 to display video an hour of two ago and had to watch it for an hour no color, poor focus, lousy purity, poor convergence and all. When a rare set comes back to life for the first time in decades ya just got stand there in awe.

[stromberg6]

Another 4 brought back!! congratulations!

[Electronic M]

Thanks! I got a thread going in this section of the forum if you want to see how it is comeing along.

[kvflyer]

Very nice. I wish I could just drop everything and work on my "stuff". But my CTC-9 is 737 miles away waiting for me to move to Florida. Can't wait...

[IsthmusTV]

I'm continuing to recap the whole chassis in stages. I also finally tested all the tubes and found a bunch that were weak, shorted or gassy and replaced them. I also carefully cleaned the tube sockets and the tuner with DeOxit applied with toothpicks and Q-Tips. The set now produces a very stable picture. (I still need to get my hands on a degaussing coil):


I decided to try a rough adjustment to the convergence, which was really bad. Things went pretty well until I got to the horizontal dynamic convergence:







None of the horizontal convergence controls seem to have any effect. Clearly, there is something amiss. I haven't begun to trouble shoot yet, as I thought I'd check in here first for advice. Any common failures to check out first? I wouldn't be surprised if the selenium rectifier is bad.

Thanks in advance.

-Clark

[Phil Nelson]

Wow, that picture is really shaping up. A bad selenium rectifier on the convergence board would not be unheard of. On my first CTC-11, when I unsoldered the legs on the selenium unit, it fell completely to pieces.



Before it was replaced, simply touching the old rectifier, or the board nearby, made the picture go nuts.

I installed new fast-response diodes that someone sent me. I don't have the type number at my fingertips. Perhaps it is buried in a past thread.

No guarantee that this will cure your problem, but the parts cost almost nothing, and selenium rectifiers are so sketchy that I routinely replace them in radio restorations, just like electrolytic capacitors.

Phil Nelson

[Ampico-kid]

I don't claim to be an expert with convergence, but the first thing that jumped out at me when I saw your picture is that it appears the static convergence is off...most notably the Blue lateral adjustment. This is the control on the neck of the crt closest to the socket that moves the blue beam left and right.

I would guess that you haven't tried to perform a full static convergence yet. Using a Dot/Bar generator and set to dots, the goal is to end up with a pure white dot in the center of the screen, using the three static convergence magnets on the neck of the crt. The Blue lateral is also used to obtain that white dot. Once you've got the center white dot the rest of the screen is converged using the Dynamic convergence controls on your convergence board.

I've never seen a perfectly converged vintage color TV. I think the goal is to get it as good as you can and be happy with it. It most definitely does take some artistic and creative maneuvering to get the picture to look good since many of the controls interact with each other.

I would say if you can sit at a distance of about 6 ft. to 8 ft. from the screen and it looks good...you've succeeded.

Hope that helps......
Bob

[Steve D.]

You really need to get your hands on a degaussing coil and start the purity process before attempting any serious convergence procedures. Other wise you'll drive yourself nuts and get very frustrated achieving that "perfect" convergence.

-Steve D.

[IsthmusTV]

Thanks, Phil, Steve and Bob, those are all good suggestions. I did try static convergence first, and I could get the blue dot to move only so far. The lateral positioning magnet did have a large effect on the static convergence, but it's very loose when I rotate it. Is is possible that I need to reposition the convergence yoke?

I think I'll back off for a while until I get a degaussing coil and can preform the purity adjustments.

-Clark

[Ampico-kid]

Originally Posted by IsthmusTV

I did try static convergence first, and I could get the blue dot to move only so far. The lateral positioning magnet did have a large effect on the static convergence, but it's very loose when I rotate it. Is is possible that I need to reposition the convergence yoke?
-Clark

If you pull the sliding magnet out of it's respective track for whatever particular color is giving you grief, and rotate it 180 degrees and then reinsert it, that might give you the movement that you need to align the beams.

You certainly can move the convergence yoke around to find the most effective position for it. Sometimes just a slight rotation right or left will bring things more into alignment. And as was mentioned by Steve, before you go any further...get your hands on a good degaussing coil and get the purity set up properly.

[IsthmusTV]

I finally got a degaussing coil which definitely helped the situation. I tried another stab at a rough convergence and this time I got much better results:


Here are a few screen shots:






As you can see from Dorothy's purple hand, I still have purity issues to deal with. I have also been experiencing intermittent horizontal jaggies (I don't know how else to describe it). You can see it in the screen shots to varying degrees. It's probably from a bad maroon drop cap from among the 20-30 that I have yet to replace. But overall, I'm very happy with how this set is shaping up. I ran it for over four hours straight last night (watched the Broncos & Patriots) and while the power transformer got pretty warm, it was never too hot for me to keep my hand on it. I still haven't measured the HOT cathode current or the HV. But they are high on my list of tasks left to do.

-Clark

[miniman82]

On the crosshatch pattern, see how right after every horizontal line there's a little hump in the vertical line? Your horizontal wave shaping coil needs to be adjusted, that's the step in Sams where you scope the coil and turn the slug till you see equal humps.