Possible delay line problem?
 

My CTC 7 has developed a slight case of ghosts. The set performs well in all respects except for a slight shadow to the right of the image. It’s reminiscent of the need to adjust the rabbit ears to clear it up. This isn’t the case however. Signals from a directly connected DVD player or over the air via a B-T modulator give the same result. Could this be caused by a defective delay line? Resistance through the line is approximately 100 ohms but from the ground connection to either end of the line shows a resistance of 1400 ohms.

I know there is a capacitance present but there should be no resistance between the coil and shield if memory serves. The horizontal, vertical sync and color are good. The AGC voltage is set to 10 volts P-P but see saw’s roughly 1-2 volts either side depending on scene content. This I don’t remember much about because AGC troubles were rare in my service experience which dates back to the early 70’s working on sets of this vintage that were still in use. Anyone have any ideas or opinions?

Could you post a photo of a screen shot?

Posting a picture would help.

Without seeing a picture:
Before blaming the delay line, you might want to check any peaking coils associated with it to see if they have opened; also check resistor values in that area. Also, check coils associated with the video detector.

Does the ghost change with adjustment of the fine tuning? If so, the problem could be in the video IF. A bad decoupling capacitor could upset the IF response.

A defective delay line will cause the color and B & W images to not register. The delay line only affects B & W video. If the fine tuner affects the ghosts, it is more likely a defective mixer or IF tube. If the fine tuner does not affect it, look for a mismatch in the antenna circuit.

A ringing/'ghosting' symptom can be caused by a bad last IF tube. Try subbing that tube for the heck of it.

Jumper around it if you suspect it, all that will happen is the chromatic information will be offset from the monochrome part of the picture. Might be difficult to pick out if there's ghosting going on in that state, but you should still be able to see it.

Thanks for all the input. I didn’t get a screen shot before dismantling the set to clean a noisy pot so I can’t post one at the moment. The fine tuning doesn’t affect this symptom at all.

I’ve checked the peaking coils and all are good except L17 (series peaking coil) feeding the video output tube grid which is open. Specs are 11 ohm coil at 250 microhenries wound on an 8200 ohm resistor.

I’m not familiar with their exact function but is it possible to rewind these or do I stand a better chance of finding a good replacement?

Replace that coil, try it again.

I replaced the oscillator and 3rd video IF tubes and for kicks wound an 11 ohm coil around an 8.2K half watt resistor and installed it in place of L17. None of these changes seem to make any difference. The screen shot below shows the defect. I am going to pull the chassis again and check the video detector circuit for abnormalities tomorrow.

I'm afraid it's hard to tell from the photo. It's generally blurry and shows some misconvergence. Not sure if the blur is your set or the camera focus.

Are you talking about the faint ghost that's about 1/2 the width of the tie, to its right? This looks wide enough that it might be a reflection in the delay line due to mistermination. How does the series 1800 ohms and 180 microhenry that loads the delay line look?

I enhanced the contrast to show the wide ghost plainly

Ditto on the termination, looks like Y line ghosting.

Yes, a delay line will definitely cause the problem. I ran into this once on a CTC9. One way to check it is to throw a jumper lead across the delay line and see if the ghosting disappears. Of course the luminescence and color won't match up, but the ghosting will be gone. If the ghosting is gone, the delay line is the culprit. Probably shorted turns in the line itself. Just match one up from a similar set and replace it.

I'm having a similar problem with my admiral ctc-12 clone , perhaps my delay line let go ? how did you make out with yours ?

mike

You should consider that in anyway the delay line must have a very low resistance between its ends and an infinite resistance respect the ground. Of course these measures must be done disconnecting its terminals from the circuit.

Sorry I’ve not been on the forum lately. In September ‘13 sent the chassis to a shop in Ohio specializing in restoration of these sets for a full factory spec alignment. They did an excellent job but after getting it installed last fall it is still slightly noticeable. Running the video through “stabilizer” before the modulator makes an improvement if still slightly noticeable so I decided I was being too critical of a 54 year old set. At normal viewing distance you have to look hard to see it so decided to give it and myself a break and just enjoy the set. But don’t think for a minute that I wouldn’t yank the chassis if I could find an NOS delay line to compare performance with.

It was during the re-install and set up that I noticed an occasionally vertical roll associated with a slight arc noise in the picture (another thread exists about that). After exhaustive testing (and driving myself crazy) it has been localized as internal to the CRT. Fortunately the set makes a beautiful picture with plenty of quality long before the brightness setting gets high enough to cause it to arc. The CRT tests fine with well over 100% emission on each gun and excellent tracking. It was a new tube date coded for ’61 instead of a rebuilt CRT.

As soon as I get time I have 3 B-T modulators set for our original locals 3,9 and 12 so I can use the set with rabbit ears the way TV is supposed to b viewed. We have Antenna TV and Me TV over the air locally so these will be two sources as well as a computer I’m configuring for use as a video server to program what I want. After all, I can’t show this set to a 16 year old without letting them have a go at using the remote control. The first thing they notice is the weight of the remote and then the sound of the tuning drive motor and most of them say “NO WAY”. That makes it all worthwhile for me. I’ve attached a photo of the set. Once I get the screens set up I’ll post a few screen shots.

Thanks guys for all your help and suggestion on this issue as well as the arcing thread. You guys are the best.
Rick