My CTC-16XL Project.

[trinescope]

It's possible that there is IF misalignment which can cause a no color condition if somehow the high video frequencies (where the color information lies) are being attenuated. The only sure way to know is to attempt the alignment procedure with proper equipment, in this case a sweep generator, preferably with frequency markers. This kind of equipment should be available cheaply all over ebay these days since they're no longer useful for servicing modern sets.

You are going to need to do some troubleshooting in addition to shotgun parts replacement if you want to find and fix the problems you are having. The CTC16 is capable of pretty good performance when set up right, I had one about 30 years ago that played really well, so you'll get yours working in time. The fact that you get color with an injected video signal tells me your problem is with the tuner or IF stages, so focus your troubleshooting over there.

[old_tv_nut]

You should not worry about resistors that are in tolerance, even "just within." Carbon composition resistors commonly were run off the assembly line, measured, and those within 5% were marked 5%, then the remaining ones within 10% were marked 10% (but they were really all off by at least plus 6% or minus 6%) and so on. So, it is very common in old consumer gear to find resistors that are just within tolerance. The sets were built that way.

There is no way to know if the IF alignment is screwed up without actually measuring it.

[Yamamaya42]

The problem with me attempting any kind of IF alignment is...
I have never done it before and have no experience in doing so, and have read that it is not easy to do.
Anything you get from ebay will be in an unknown state functionality wise, and not be in calibration and missing vital input / output probes that can affect the tests you are trying to do, some of which you may try to recreate, but this too can have an affect on the end result.

Right now it seems to be working mostly OK with the injected video, the only issue is the retrace lines that pop up from time to time, which might unavoidable at this point, not sure, given that the normal path of input ( with AGC and everything ) is bypassed.

As I mentioned before, It's unlikely I can ever do an IF alignment myself on it

[Rocket]

Great to see how good the picture is looking so far! What a crazy journey to get this working and amazing with how messed up this was from the previous owner. Cant wait to see what it looks like once the cataract surgery is done

[old_coot88]

Originally Posted by Yamamaya42

As I mentioned before, It's unlikely I can ever do an IF alignment myself on it

Maybe consider transplanting the whole IF board from an unmolested donor chassis(?).

[Yamamaya42]

Originally Posted by old_coot88

Maybe consider transplanting the whole IF board from an unmolested donor chassis(?).

Unlikely scenario, due to the following.

The chances of ever coming across another CTC16-XL chassis with a viable IF board to use as host astronomically small, and where as the CTC16 is very close to the XL, it's not the same, so it's not viable, furthermore, from what I understand, the IF section is RF tuned to the given characteristics of the tuner installed in the set, so in the very off chance one was ever found, if you tried to use it, it would no longer be matched to the tuner.

My only hope is, if I ever want to get IF working again, is there is a shop within 40 miles that does antique / vintage TV work, and they inform me that they do have a working sweep marker generator, and once I am done with all my repairs, if I really wanted to, they can do the IF alignment.

[trinescope]

If you're somewhere around Dallas/Fort Worth I'd be willing to do the alignment free of charge. I don't believe these sets were aligned somehow "matching" the tuner; in fact many set makers bought their tuners from outside sources rather than making the tuners themselves. Otherwise the alignment curves would show something other than marker frequencies in the IF range. Rather the IF was set up to manufacturer specs and the tuner done so separately and then the two should get along well afterwards. Tuners generally don't need much in the way of alignment unless something bad happened. All they really have to do is reject signals outside of the selected channel; all the other frequency traps and response shaping adjustments are in the IF strip.

[Yamamaya42]

Originally Posted by trinescope

If you're somewhere around Dallas/Fort Worth I'd be willing to do the alignment free of charge. I don't believe these sets were aligned somehow "matching" the tuner; in fact many set makers bought their tuners from outside sources rather than making the tuners themselves. Otherwise the alignment curves would show something other than marker frequencies in the IF range. Rather the IF was set up to manufacturer specs and the tuner done so separately and then the two should get along well afterwards. Tuners generally don't need much in the way of alignment unless something bad happened. All they really have to do is reject signals outside of the selected channel; all the other frequency traps and response shaping adjustments are in the IF strip.

Almost, but not quite
I'm in the Austin area, 20 miles north, Round Rock. the place I was referring to is Dean TV Repair on N, N Lamar Blvd here.

[old_coot88]

Originally Posted by trinescope

the IF was set up to manufacturer specs and the tuner done so separately and then the two should get along well afterwards. Tuners generally don't need much in the way of alignment unless something bad happened.

There is usually an item in the tuner called the 'mixer plate coil', and if it's adjustable, it is part of the IF alignment. If I remember correctly, the RCAs took the mini hex tool for that adjustment.

[trinescope]

I had to look at the alignment instructions for this chassis and yes you are correct. That coil, although part of the tuner, is actually on the IF side so yes, it would be part of the procedure since it's really part of the IF strip. I'm guessing its response is a bit more broadband than the other adjustments.

[old_tv_nut]

Originally Posted by trinescope

I had to look at the alignment instructions for this chassis and yes you are correct. That coil, although part of the tuner, is actually on the IF side so yes, it would be part of the procedure since it's really part of the IF strip. I'm guessing its response is a bit more broadband than the other adjustments.

Since the instructions are just to tune for max at 44 Mhz (mid band), it does seem likely it's broadband. It's a simple adjustment in any case, even if it does affect the tilt somewhat.

[Yamamaya42]

https://imgur.com/Ae7nlTV

getting ready for cataract fix day


I am seeing a tiny bit of image ghosting, most likely due to the video injection, and not much I can do about it. (guess) I have no real i idea what is doing it.

but did notice...

snip / paste
old_tv_nut
"Duh.. I think I'm awake today... If you use a coupling cap and remove L9, you will need to add a grid bias resistor (say, 100k) from G1 to ground. "

Bit on the SAMs. it says,
V3 pin7 (grid) 130 ohm polarity dependent, could 100k be too high?
I think I'll try 500k or lower and see if it makes any difference.

[old_tv_nut]

130 ohms is what you read with the circuit intact. The tube does not need such a low resistance to ground, it just happens to be what is there when the normal circuit is connected.

If you are coupling through a capacitor, you need some resistance to ground to bias the tube, but the smaller you make this resistance, the larger the coupling capacitor you will need to keep video low-frequency response. with 100k load, you need a capacitor of about 0.1 microfarad. If you use 50k ohms (47k standard value), you need a capacitor twice as big, and so on.

[Yamamaya42]

so i guess the slight image ghosting is unavoidable at this point? I cant think of anything else to do about it really.

[old_tv_nut]

"Slight ghosting image" isn't a specific enough comment to guess about. Can't tell how much is "slight," is it really a ghost or more of a smear or ringing, etc. - would have to see it. In any case, your video amplifier and the coupling capacitor would not cause it. I think you should wait to do more nitpicking after the cataract is removed.