Thanks, yes I plan on doing a complete alignment. Early on I decided to leave the tuner as-is (other than contact general cleaning) until I had the rest of the chassis re-capd. I want to replace only the out-of-tolerance resistors in the tuner. Then I will do the full alignment. The IF seems response seems pretty good right now, but there is more noise in the video than I would expect. I may try changing the IF tubes first though.

Dave

Thanks, and your 21CT55 produces really great looking images. Mine had most of the original paper capacitors, which I tested with a Sencore LC-75. All the paper caps showed leakage, so I replaced them all. ALL of my white peaking coils were open, so I replaced them as well. I replaced all resistors that were off by more than +/-7% and increased the wattage rating. I am guessing that the resistors that increase in value is due to heat from not being able to handle the load. I did end up using a few of the yellow film caps, which I have used with no problems in my B/W sets.
After reading all the posts here, I wanted to try my hand at doing the restoration of my 21CT55 on my own, and ask for help here when I got stuck. So far so good. I also wanted to share the problems I ran into in case others find something similar.
I will see if I can order the Wizard of Oz and will also look for "Digital Video Evaluation" DVD's test patterns.
My camera is a cheap 7 Mpixel auto everything which probably will not be good enough to take good pictures in a dark room. How do you post high res pictures here?

21-ct-55
 

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Nice job getting it working.

Sounds just like mine. Clip one lead of a part to test it and find two more underneath that also need tested and replaced.

My guess is that the RCA service manual schematic shows the original design and maybe the Sams shows the production run changes.

Same here. I have restored my CTC3 chassis with the same part values it came with. I works, but my first attempt at convergence was not so good. I want to try the Sams changes to see if that helps.

My seleniums were long gone, so I put the modern diodes and dropping resistors under the old rectifier cover.

I am going to try that next, even though tuner lead dress seems like black magic to me.


I also restored the main chassis and HV section, ran socket resistance checks, power supply tests, socket voltage checks, and audio and video tests with a VA62 using a scope to trace signals through the set before I got the CRT connected. I was holding my breath at the first power up with the CRT in it hoping that the vacuum was good enough to not get the CRT tube neck glow. I felt like I won the lottery when a picture showed up.

Here's hoping you have good luck too! Hope you get better soon. I know its hard to be patient but these sets weigh a ton and you don't want to injure yourself or the set. Its probably best to take your time with the restoration and wait until you are back at 100% before moving that heavy chassis. Better yet, maybe you can get some help moving it.

Dave

CTC2 rf-if info
 

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The CTC-2/B chassis are unlike any other that came after, as far as alignment goes. There are many more stages, so more things that can go wrong. I would not recommend attempting an alignment on this thing unless you REALLY know what you're doing. When I got my CT-100, it was all out of whack. I tried doing an overall response on of it, but it was no use. I ended up peaking each IF stage by itself, then doing an overall response curve to touch things up. The B&K rig really helps out on that. Still took me over 2 weeks...

Gulp.. Wish I new that earlier. I replaced a bunch of bad resistors in my tuner yesterday and this afternoon began the audio and picture IF alignment process. So far I have only gotten through the audio and 5th video alignment. My sweep generator is acting flakey, but I did manage to get the alignment to match the fig. 15 5th IF response sweep plot. There are markers in the dips are 41.25 and 47.25 MHz. There is a marker at 42.17 and 45.75 in the high gain area. The other marker-like stuff must be from having the 5th IF bottom and top covers off, I guess. Guess I'm committed at this point. I have only aligned three B/W set so far, so its trial by fire for me on this..

Dave

After two attempts and hours of tweaking I have working set. Nick was so right, the CTC2B is very tough to align, at least for me. Here is a picture of the sweep response from the tuner crystal to the video detector test point. Not as high a peak at 41.65 as RCA shows but the others freqs are not bad. I ended up using the Sencore VA62 10 freq multiburst to do the video traps and bandpass alignment. And I finally realized my color bar generator needs alignment. So please ignore my info on the RCA to VA62 color comparison. I used a Heathkit IO-101 I picked up at this years ETF convention to get the correct color bars to do the color alignment. Here are also some pictures of my flyback temperature using a fan to keep it cool and leaving off the corner cover as a vent. The fan keeps the flyback just warm to the touch after running for hours at about 205mA. And a pic of some cartoon color.

And here are some Wizard of Oz pictures.

I still need to find the source of a white vertical line that moves horizontally as I adjust the horz hold control. The line does not go away when I adjust the H drive. Any ideas? I do not have a metal screen to cover the opening under the chassis, could it be due to that?

It looks like it could be something during retrace not being blanked - does it move the opposite direction of the picture as you turn the horz hold?

As I rotate the H hold counter clockwise the image moves slightly to the left and the white vertical line moves to the right. So, I think it does what you described.

Yes, definitely a sign of something in the video during retrace. Does the visibility increase when you turn the brightness up? Can you see the h sync then? This would mean there's insufficient retrace blanking. (Not familiar with this schematic, so don't know what provisions there may be for blanking.)

123

Yes increasing the brightness does increase the brightness of the white vertical line along with the background brightness. If I lower the brightness so the whole screen just goes dark I can still see the vertical white line as shown on a couple of previous pictures. I could not see anything else, so I guess I do not see the h sync. With the brightness all the way up I do see some slanted retrace lines (like on the 40's BW sets), but they go away just under full brightness. Here is a screen capture of the SAMs showing the vertical blanking signal on the cathode of the CRT. My scope shows the 15V pulse riding on a 142V DC level.

I tried two other H output tubes and 1 other damper tube but could see no difference in the vertical white line. Changing the bottom H osc slug just moves the line left or right.

I notice that turning the contrast all the way down removes the vertical white line. I can then turn the brightness all the way up with no line.

If I connect the Heathkit vectorscope and use its switches to disable the CRT grid video I do not see the line. Just connecting the vectorscope leads to the CRT grids reduces the white line quite a bit. Maybe high frequency ringing occurring during the horizontal retrace somehow coupling into the video?

I am using three modern 120 mH peaking coils that drive the CRT grids. I tried substituting an old style Miller replacement 120 mH peaking coil, but it shows the same white line.

Maybe I can track it down by putting in caps to filter out the noise at places along the video processing...

Mine actually has faint banding when showing blank video, I think it's horizontal ringing. Must be something with the design of the chassis, because the CT-100 doesn't do that.

Problem solved
 

Yeah sure seemed like that to me. With blank video I put a 1500pF cap across the 1st video amp and that got rid of it. I put the cap across the 2nd IF and the vertical white line came back. So I figured the noise/ringing was getting in there somehow. Or may it is my alignment.:no:

So after being bummed about that for a while, I realized I have been feeding all my video to the 21CT55 through my DVD player and then through a cheap RF modulator. This has worked just fine for my 1940s BW sets for quite a while. Even my VA62 test patterns were going into the DVD video input to get to the set. I decided to try feeding a blank video from my VA62 through its RF output. The vertical white line was gone! :banana:

So my vertical white line has been in the RF I was feeding it, not in the set. I know that does not make sense if I could put a cap across the 2nd IF and have it come back, but the line is not there when I drive it with the VA62, so yippee, I hope.

What is the best RF modulator to feed signals to a 21CT55?

I have used a BT agile 450 and it works great, had the same kind of white line issue on an old GE 14" set that you describe, switch to the BT got rid of it. I would have chimed in sooner I just did not make the connection (between an old BW set and early color set.

here is a pic of what I was dealing with, its not a drive bar as you could detune and it would go away, and it moved with the horz hold, the BT resolved it.

That's the problem. I will see if I can get one of those. Thanks!

they pop up on ebay all the time, prices are all over the place but you should be able to get one for around 40$ if you can wait for a good deal. they use DIP switches to set the RF out channel, and just need a audio and composite video in. I think the correct name is a Blonder Tonge agile modulator, I have the 450 there are others. It can be a bit confusing so look for the correct inputs and RF outputs and the little door that hides the DIP switches in the front.

another benefit is you can adjust the audio and video modulation levels, which is good for getting rid of sync buzz on sets that do not deal with that well.

Just clicked BIN on EPay to get a BT AM-60-550B for $39.99. Thanks for the tip.

if you use is as intended (a direct connection from the modulator to the TV via cable), just make sure you set the RF out the minimum to avoid swamping the tuner. They are designed for cable tv networks and can put out a LOT of RF to drive a lot of cable. I don't want the funny cookie cutters to get mad so will not talk about xmitting ota .

you will need remember to connect the IF in and IF out with a jumper as well.

I have several of them in various models. So, if it doesn't seem to work when you get it, you may have to replace the voltage regulator and/or the filter capacitors in the power supply. Most of the ones I have purchased were OK. But the others were easily fixed with new filter caps and the regulator, easy to do, easy to get. I even got the regulator from Radio Shack of all places.

Cheers!

With the RF out cranked feeding into rabbit ears I can just barely tune it on the other end of my house, and given that there is a good deal of space between houses out here I doubt anyone else can get it or would even care if they did....

The line I believe is actually due to the other end of the sync pulse. Consider this: the other end of the sync pulse is approximately 4.7us after the horizontal sync trigger. This falls within the active picture in the middle during the horizontal retrace period and if not properly controlled, will induce a vertical white line.

The factors which induce its appearance include IF alignment or video amplifier response in conjunction with the sync generated in a DVD player perhaps having too sharp a risetime. If the overall TV's video response is not reasonably flat, this will cause an overshoot into white which shows up as a white line.

Earlier sets did not have retrace blanking which makes this more problematic. The solution is careful check of the overall video RF and more particularly the IF response.

Color chassis's and the CTC2 chassis in particular is tough to align if you do not have the correct equipment. Fortunately good equipment is available on Ebay at a reasonable price. I trust you will find better equipment.

Forty years ago when I dismissed the thought of ever acquiring Hewlett Packard test equipment to do the job. Back then, at $5K to $10K, 1970's HP equipment was certainly out of the question. In the last 10 years, (thanks to Ebay) I picked up a 1970's HP8601a and HP8600a together for less than $100. I have used these devices to align sets RF, IF and chroma sections to and often I feel more accurately to factory specifications.

Alignment can be tough and is impossible without adequate equipment. But doing it right with the right equipment always rewards your efforts.

I put a scope on the video waveform from at the grid of the first video amp and I can see a positive overshoot. Do you find that you have to reduce the high frequency IF response in order to slow the rise time to limit the overshoot?

Dave

No, I believe it is essential to make the response as close as possible to the factory specification. It may be that way it is currently aligned, the carrier is too low on the "Nyquist" slope to compensate for perhaps the higher video frequencies ("lower IF") rolloff. You can check this as I would suspect the white line will disappear when fine tuning the video carrier up the slope.

I believe the CTC2B chassis with 5 IF stages and the response going down to 21.65MHz AND the sharp transition makes it even tougher to get it right. But it can be done with the right equipment and some practice.

I recall Wayne suggested that is why the later "haystack" IF response became popular: it would get rid of the "galloping ghosts" when fine tuning and perhaps help prevent the white line. But I like the extended IF response design because I imagine if aligned right the picture will be better on a 21CT55 than on the the later CTC4's CTC5's and upward.

Terry

Thanks for the information Terry. I put the VA62 back to "external modulation" and took a look at the video at the first video amp. It did not have any video sync at all, so no sync overshoot, that's why it does not have the white line. I will take another crack at the alignment but this time I will also look at the video waveform as I move the sweep and marker generators through the stages to try to understand which has the most impact on my overshoot problem.

Well that little white vertical line, and my replacing lots of resistors in the RF and IF convinced me I should do a complete alignment of my set. Boy did that take a long time to do. But, I think I learned a lot, and got a good result. You be the judge. Here are some pictures starting with the final video waveform at the grid of the 1st video amp using a Sencore VA62 multiburst 10 bar sweep from 0 to 4.5 MHz in steps of .5 MHz. Next is the chroma sweep with the required 1st and 3rd bars the same size. Then the multiburst waveform at the green CRT grid with no color. Then the multiburst on the CRT showing a some discernable lines at 4 MHz (second bar from the right). Then color bars.

Now a few WOZ pictures.

And a few more. Yeah, I took way too many....

I promise, last ones...

Ok, I lied. A few more colorful ones.

You did NOT take too many. Just plain gorgeous!

Nice work, I really like the pictures of Nemo ! I have been playing my set off and on and do notice how the Colors do make nice eye candy :)

Another 21CT55 Operational
 

[QUOTE=Tomcomm; I hope you get the Wizard of Oz for subjective evaluation of your 21CT55 picture quality and suggest also getting the " Digital Video Evaluation" DVD's test patterns for critical setup and objective PQ evaluation. Looking forward for your full-screen width, no room light, full computer monitor posted JPGs. I know what the 21CT55's are capable of so lotsa luck finishing this one off...........Tom[/QUOTE]

Your first screen shots presented full monitor size, with total room blackout are quite good, the OZ clips are most impressive. The computer generated cartoons showed near-saturated colors with none of the natural flesh facial graduation of the OZ closeups. The OZ's subtle color graduations is where our 21CT55's low level chroma demodulation and matrixing is so apparent. Is your 21AXP22A possibly a different phosphor then the non A ? Looking forward for more "natural" screen shots....Tom