CTC-4 Director 21

[SwizzyMan]

Originally Posted by Bill R

It looks like you have made some good progress. However, you are still off on some of the basics. Do you have the Sam's for it? Sometimes the procedures are easier to follow in the Sam's. First things first, and remember all of them interact with each other. I notice from your last picture that you still do not have the vertical size and height quite right. Those blocks should all be the same size. The key is get the Black and white picture right, then worry about the color picture. I would turn the color off and forget for now. Try to get the linearity right first. Do not unplug the convergence board. Then work on purity, center static convergence, purity, static convergence, purity, static convergence. Repeat as needed until the one dot in the center is perfect. Then you can worry about dynamic convergence. Follow the steps in order and do not skip any. You will probably do it several times. Then recheck purity, and static convergence and tweek as needed and start over. It sounds intimidating, but by the time you run through it a couple of times you will get good at it and the entire thing can be done in less than an hour. Be sure the High voltage is correct, and the focus works properly. You may find it easier if you turn the brightness or contrast down some. You will get sharper lines. If you encounter any problems, make the necessary repair before proceeding. Now, it is time to do the gray scale adjustments. After all this you should have a nearly perfect black and white picture. Now you can turn the color up and start working on the color circuits. If you put any capacitor or part in that was not there originally, remove it. It wasn't necessary when new and shouldn't be necessary now. Be sure and check all the circuit grounds, and tube sockets. They are trouble areas. I would try a color alignment. Follow the steps in order. It is not hard. Usually you will ground a test point to let the oscillator free run and adjust the coil until the bars are stable, or only move very slowly. You will then remove the jumper and if the color oscillator, and bandpass amp are working the color should lock in solid. If not you will need to do some troubleshooting and do it again. Once color locks in it may be wrong so that will be adjusted next. You will center the tint control and adjust the transformers in the demodulator circuit for correct flesh tones and proper tint range. It is a balancing act. Now you should have a good color picture with proper tint range. Notice that unless you are using a vectorscope I have not mentioned any color bars. The early procedures use a keyed rainbow pattern, not the NTSC pattern you are using. You do still have an IF alignment issue since the color does not quite fit the black and white picture. On your color bars you can see it as the intensity of the color bar dropping off near the edge of the bar, or bleeding onto the next bar. Do carefully check the caps and resistors in the IF strip since some could have drifted off value. Replacing the drifted components may fix the problem without doing an alignment. DO NOT attempt this alignment without the proper equipment. You would need a Sweep marker generator, Oscilloscope with demodulator probe, and a bias power supply.
You are making great progress, just remember to try not to get ahead of yourself. You will end up chasing problems that may not really be there.

Thanks you for the detailed instructions. I will do linearity first. The Black and White picture is already pretty solid aside from vertical linearity and height. If push comes to shove with the IF, I can always inject a composite signal into the grid of the video amp tube.

[Phil Nelson]

Originally Posted by SwizzyMan

If push comes to shove with the IF, I can always inject a composite signal into the grid of the video amp tube.

That's what I had hoped, too, but video injection is not as simple on the CTC-4 as in typical BW sets. The last two sections in the article at https://antiqueradio.org/RCACTC-4ColorTelevision.htm discuss this issue.

Executive summary: video injection requires adding a video preamp as described in the 1956 RCA Broadcast News article. I did breadboard such a preamp, but version 1.0 was disappointing and I set the project aside to work on other stuff for a while.

On the positive side, those are pretty true-looking color bars. You are not far from having a very watchable CTC-4. The edge convergence might never be as good as the center convergence, but that's common in early color roundies. Whichever manual you follow, take Bill's advice -- go step by step in the order shown and do not skip steps.

Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html

[SwizzyMan]

This is the best I can get on height and linearity. As you can see the height isnt quite high enough. I swapped vertical out tubes with a bit of improvement. Hmmm, usually insufficient vertical height would indicate bad filters maybe, but all have been replaced so it must be something else.

[SwizzyMan]

Originally Posted by Phil Nelson

That's what I had hoped, too, but video injection is not as simple on the CTC-4 as in typical BW sets. The last two sections in the article at https://antiqueradio.org/RCACTC-4ColorTelevision.htm discuss this issue.

Executive summary: video injection requires adding a video preamp as described in the 1956 RCA Broadcast News article. I did breadboard such a preamp, but version 1.0 was disappointing and I set the project aside to work on other stuff for a while.

On the positive side, those are pretty true-looking color bars. You are not far from having a very watchable CTC-4. The edge convergence might never be as good as the center convergence, but that's common in early color roundies. Whichever manual you follow, take Bill's advice -- go step by step in the order shown and do not skip steps.

Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html

I had a feeling that it would be a bit more than just injecting a signal into the grid. I originally was under the impression that this was able to be done. Member DaveWM paid a visit to my place and suggested that I should try this. Not sure if he knew that there was more to it than just injecting a direct video source. Or hopefully he was right? He has worked on a couple early color sets so maybe he was on to something?

[SwizzyMan]

I will be out of town for the 4th until next Wednesday. While I am gone, I will do some reading through the manuals and gather some extra info on the problem areas. Until then stay tuned! Everyone have a happy 4th of July and I'll be back on this set next week!

[Bill R]

You likely have some bad capacitors in the vertical stage still. If you could put a circle pattern up from a generator or dvd, you can adjust for a perfect circle then you will see if the raster will fill the screen. Also check the circuit grounds in the vertical output stage. B+ could be a little low. If it is to low the picture will usually pull in horizontally some. Be sure and check the resistors as well. There may be some that have drifted high in value.

[SwizzyMan]

After leaving no stone unturned in the vertical circuit (which isnt many). I found only one barely out of tolerance resistor a 2.2meg 1/2w coming off G1 of the 6AQ5 vertical amp then goes to ground. Not sure it is too critical and its just barely off spec I mean like less than 1% off spec so I might just leave it. All caps are fine except I did replace a .039 which comes off the plate of the vertical amp and goes to the red cathode of the CRT. The original the maroon drop cap tested OK but I had a cap on hand and replaced it. Dont think it will make the vertical any higher though..

[Bill R]

Originally Posted by SwizzyMan

After leaving no stone unturned in the vertical circuit (which isnt many). I found only one barely out of tolerance resistor a 2.2meg 1/2w coming off G1 of the 6AQ5 vertical amp then goes to ground. Not sure it is too critical and its just barely off spec I mean like less than 1% off spec so I might just leave it. All caps are fine except I did replace a .039 which comes off the plate of the vertical amp and goes to the red cathode of the CRT. The original the maroon drop cap tested OK but I had a cap on hand and replaced it. Dont think it will make the vertical any higher though..

I would probably replace that resistor. Also how does the B+ look? 380V? Also I might replace c169 even if it tested good. Also don't rule out a weak tube.

[miniman82]

Lack of height is nearly always drifted dropping resistors coming from B+boost so look at R119, the height pot, R117 and R118. If they all spec out, lower the value of R119 till the picture fills the screen. If I had to guess our vertical output transformers are going soft slowly, only solution is to feed them more voltage. Those are Sams resistors BTW.

[SwizzyMan]

Originally Posted by miniman82

Lack of height is nearly always drifted dropping resistors coming from B+boost so look at R119, the height pot, R117 and R118. If they all spec out, lower the value of R119 till the picture fills the screen. If I had to guess our vertical output transformers are going soft slowly, only solution is to feed them more voltage. Those are Sams resistors BTW.

All check out fine. R117 is just barely in spec but I don't think that this will be an issue. B+ is 399 but know that I havent added any dropping resistors to the 4007 diodes in place of the seleniums so that should explain the high B+. Looks like I need to experiment with different values for R119.

[old_tv_nut]

Hmm... can you measure the high voltage? If it's high, it may reduce the scan size.

Also, if you have a variac, try adjusting the line voltage.

[SwizzyMan]

Originally Posted by old_tv_nut

Hmm... can you measure the high voltage? If it's high, it may reduce the scan size.

Also, if you have a variac, try adjusting the line voltage.

Now that you mention it. I have been running the set off my PR57 and when the set is at full operation it does drag the line voltage down about maybe 5 volts. I never thought of adjusting the line voltage after the set has warmed up. This may be the source of my lack of height.

[SwizzyMan]

Great, now I have even less height and now fold over! Looks like I need to retrace my steps here. All I did was replace a cap. I did clip the leg of a few resistors and soldered them back in. I will start by checking my connections on the resistors and cap.

[old_coot88]

I would run the vert. hold stop-to-stop before diving into it again. It may be locking at an odd sweep rate.

Also, on the line voltage issue, measure the heater voltage. If it's running signifigantly above or below the nominal 6.3 VAC, it'll tell you whether the line voltage is kosher or not.

[SwizzyMan]

Originally Posted by old_coot88

I would run the vert. hold stop-to-stop before diving into it again. It may be locking at an odd sweep rate.

Good thing I traced my work back because I forgot to solder a cap back in circuit. All is fine now. Linearity isnt great but I got it as best as I can. I still think I might lower the value of r119.