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  #31  
Old 01-22-2016, 10:13 AM
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CTC-5 CRT setup procedure

See the setup procedure attached.

Regarding the resistance readings of the delay line in circuit, it is very complicated to tell what they should be because you are measuring everything connected to it. The only way to be sure is to have readings from a good set to compare to.

The alternative is to disconnect the line and see what readings you get of the line by itself. There should be conduction from the input to the output and no conduction from either the input or output to ground.

I'm not sure what the normal resistance is between input and output, but I suspect it will be low, as theoretically the line is supposed to work by a combination of distributed inductance (the coil) and distributed capacitance (the coil is wound on a thin insulator over a ground foil).
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File Type: pdf CRT setup pp 41-42 small.pdf (680.6 KB, 23 views)
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  #32  
Old 01-22-2016, 12:49 PM
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Possibly a reasonable test would be to simply by-pass the delay line and observe if contrast is greatly improved? :

Of course the picture would be a little strange looking, as the luminance signal would be slightly ahead of the color signal, but it should give you an indication of the operation of the delay line.

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  #33  
Old 01-22-2016, 04:29 PM
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How would I replace the delay line if it might be bad? The setup procedures did not seem to do anything. Maybe something in the contrast circuit could be bad?
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  #34  
Old 01-23-2016, 05:05 PM
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Starting to think that the delay line is not the issue here. I can get an OK crisp picture but only with the contrast, color,and brightness turned down pretty far. Only watchable in a dark room. I checked two of the pins on the 12BY7A video output tube (plate and screen grid) and found that both voltages on the pins are off. This must be an issue with a resistor in the 12BY7A portion of the board. I must note I wired in parallel two 1 uf film caps to create a 2uf cap to replace the electrolytic that was there. The schematic calls for a 2 uf cap but the one I removed was an 8 uf. I never found any production changes stating that a 8 uf should be used instead of a 2 uf. Maybe I should try an 8 uf?
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  #35  
Old 01-23-2016, 10:42 PM
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If it's any consolation, I have never been satisfied with the luma drive level on my CTC-5. It seems the chroma sections have much more capability. It's on my "some day" list to revisit this issue, but now that it's been brought up, maybe someone else here can comment.

One thought: check the AGC and make sure you have the proper video level at the video detector. Also try substituting video output tubes. In the Magnavox set I had, I found that the output tubes varied quite a bit and you could get more gain out of some than others. I think the luma channel is really pushing to get enough gain out of the final tube.
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  #36  
Old 01-24-2016, 10:26 AM
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perhaps a contrast mod would be wise?
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  #37  
Old 01-24-2016, 02:03 PM
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Quote:
Originally Posted by SwizzyMan View Post
perhaps a contrast mod would be wise?
I think it couldn't hurt. Just be careful and don't get the control reversed like I did. It works OK if you do, but max contrast is counterclockwise.
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  #38  
Old 01-24-2016, 03:38 PM
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Quote:
Originally Posted by old_tv_nut View Post
I think it couldn't hurt. Just be careful and don't get the control reversed like I did. It works OK if you do, but max contrast is counterclockwise.
Did you wire the pot up like in a ctc7 or ctc9 or perhaps a different type of mod? Add another video stage, perhaps?

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  #39  
Old 01-24-2016, 04:38 PM
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Here's the mod. I posted it in 2008, but it looks like it has disappeared.
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File Type: jpg ContrastMod.jpg (140.7 KB, 52 views)
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  #40  
Old 01-24-2016, 05:26 PM
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Thanks for posting! I guess it looks more like the early ctc7 circuit versions, with the 3900pf cap. The text appears to be correct, but the schematic appears to not show the ground connection for the cold end of the pot/- of the cap/1k resistor.

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  #41  
Old 01-25-2016, 04:55 PM
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Installed the contrast mod. I went with a 3300 pf cap instead of a 3900 because it gives a crisper picture. Picture looks PERFECT. I didn't know a super chassis could create such a pretty picture! Almost done here. Need to do edge purity, convergence, and measure the cathode current on the 6CB5A and adjust it if necessary. How does the picture look to all of you? Good color?
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File Type: jpg IMG_1212.jpg (61.3 KB, 93 views)
File Type: jpg IMG_1213.jpg (53.8 KB, 84 views)
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  #42  
Old 01-26-2016, 04:30 PM
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Did some work with the convergence. This set is a real pain in the ass to converge but I do like that all the adjustments are on the front panel. Have a blooming issue now. Comes and goes. Not too noticeable but does get annoying.
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  #43  
Old 01-26-2016, 04:55 PM
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Looking good. Remember convergence only needs to look good at 10 feet, so don't drive yourself insane if you have one corner that's not as good as the others.
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  #44  
Old 01-26-2016, 04:58 PM
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Screenshot looks good now, just don't drive yourself batty with the convergence like Wayne said. It's never perfect, just get it close an enjoy!
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  #45  
Old 01-26-2016, 05:18 PM
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Well then I will do an edge purity and check HOT cathode current and install a flyback fan. Will finish up this weekend.
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