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.)

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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?