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  #1  
Old 07-17-2016, 02:11 PM
Philco123 Philco123 is offline
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Wanted: Color TV Repair Service

Looking for a talented soul to work on my CTC-7 Sanford chassis. Chassis was recapped by me and tuner was re-aligned as best as possible by Mr. Nick Williams (thank you Nick!). After much work, the picture is still scrambled and rolling. Folks, the chassis has potential and was probably taken to third base and beyond with all the work, however it's beyond my capabilities to get it across home plate. Would like to see the ole girl up and running again. Willing to transport. All inquiries welcome. 734-788-5085.
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Old 07-17-2016, 03:03 PM
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miniman82 miniman82 is offline
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I think there's probably still something amiss with the IF, or possibly the detector circuit. I got the best response curve I was able to, but the slope adjustment still seemed a little wonky to me. I just hope it doesn't become another one of those chassis with silver mica disease, where you end up replacing a bunch of stuff inside those little cans. It can be a real headache, and then of course you have to realign the whole thing after you're done finding the problem.
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Old 07-17-2016, 05:28 PM
DaveWM DaveWM is online now
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sync issue? is that what scrambled and rolling means?
IF its a sync issue you may want to look into the noise inverter setup and the AGC procedure, look into AGC, scope the AGC output for hash (filter cap).
Scope the output from the sync separator. look for video noise getting thru.

Last edited by DaveWM; 07-17-2016 at 06:12 PM.
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Old 07-17-2016, 07:39 PM
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miniman82 miniman82 is offline
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Seems more like 'weak' IF output to me; while I could get a response curve on my scope, I had all the controls on my sweep rig nearly maxed out when I did it. AGC works like it should, it just doesn't seem like there's enough of a signal for the set to lock on to. Before he brought it to me I suggested trying new detector diodes, since I had run into a similar issue on a set before. Didn't seem to make much difference at all. The tuner also doesn't seem right to me, the fine tuning has to be all the way to one side in order to pick anything up and the channel slugs don't have much effect. If it were mine, I would just as soon convert it to composite input to cure the problem. OTA is dead and gone anyway for most people, and a direct connection gives better image quality anyway. Just a lot of problems with it, doesn't seem worthwhile to spend a bunch of time fixing when there's already a better solution.
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Old 07-18-2016, 07:02 PM
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Tubejunke Tubejunke is offline
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Just curious. What are you using for the main input? A VCR, a DVD, maybe a digital converter OTA? I have had a lot of quirky issues with signal input ever since analog OTA left the game. One would think it's the set, but I have proven that not to be true in several cases. However, in those cases it was more of a very weak signal; or fuzzy video with no or low sound. Not sync issues....
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Old 07-18-2016, 08:38 PM
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We tried 3 different color bar generators, but since those same units work fine on other sets its got to be the chassis this time.
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Old 07-18-2016, 09:30 PM
Philco123 Philco123 is offline
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After speaking with a seasoned and very knowledgable roundie collector this morning (thank you Dave), I was advised of the importance of replacing the .01 microfarad/400v capacitor on the IF board (failed to do up up to this point). This one cap may be the root cause of the sync issues this Sanford has been experiencing. Additionally, the heat from soldering in the detector diodes may have cooked the internal Ge elements, rendering them useless. I will report back after replacing the .01 microfarad cap on the IF board (on order) and replace the detector diodes using heat sinks (alligator clips) during the soldering process.

I want to thank Nick, Dave and other VK members who have provided immeasurable help, guidance, advice and troubleshooting techniques to me as I attempt to get this CTC-7 up and running again. More to follow.
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Old 07-19-2016, 09:06 AM
DaveWM DaveWM is online now
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https://www.youtube.com/watch?v=GBx20sjJN7o

Hopefully this will be it, if not the best approach would be to signal inject.

But before that I would look at the AGC voltage to make sure its working as it should. A scope is best to see the AGC, but with out that at least a meter to see what the actual voltage is.

I use a BK-1076 just for this purpose. You can start at the video out tube with a composite signal, if ok then start working back with an IF signal at each stage of the IF until the loss of signal is noted. This is approach is the fastest way to narrow down the weak signal.

I generally will also use a variable DC supply to confirm the AGC is working as it should. This is part of my 1076 so what I do is hook up the AGC play with that 1st then start the injection project.


For future reference if there is ever a sync issue the 1st place to check is the AGC, clipping the sync pulse on to strong a signal. Generally the picture has to be way overloaded (dark) for this to start happening though.

next would be is the sync just vert or both vert and horz? you can try tube subbing the sync sep tube. If that does not clear it a scope on the output of the sync separator will confirm the issue is limited to the sync pulses. from there you can voltage check to find the issue.

On this set the orig problem was sync both vert and horz, if it had only been vert I would have looked at the vertical integrater but since it was both more likely the sync signal was suspect. The cap noted by the OP is C321 which is the coupling cap for the sycn sep grid. Leakage there will def cause a problem with the bias and function of the tube.

Last edited by DaveWM; 07-19-2016 at 09:12 AM.
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Old 07-19-2016, 07:25 PM
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miniman82 miniman82 is offline
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I suppose I should have scoped for sync pulses in the respective oscillators, but with the tuner troubles I really didn't think it would be of any diagnostic importance. We already knew the signal was weak at the detector, which is why I was leaning towards a wore out tube or something mechanically wrong in the tuner itself.

Good luck Jeff, and if replacing that cap helps it any you might want to bring it back so I can touch up the IF response. No doubt I can do a better job of it if things improve.
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Old 07-19-2016, 07:38 PM
DaveWM DaveWM is online now
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The initial problem was sync before any recapping took place. The likely issue was that cap.

Now we have a new problem, signal. Since the diodes were replaced without the use of heat sinks, there is a chance they were damaged by heat.

The Tuner was working before the recapping so I am hoping it still is.

What will really help with long distance diagnostics is a picture of what is going on. Hopefully there will be video of the set in operation.

It was also discussed with the owner that tubes should always be suspect, and tube testers are of limited value, so substitution is always the 1st choice in tv repair.
Typically if sync is an issue then the sync sep tube would be subbed 1st. If that does not correct then a minor adj of agc may clear it but more likely there is a problem in the circuit. This should be analyzed with a scope to narrow the problem, typically voltage checks will further narrow down and then finally component checks. Old circuits typically suffer from in this order

film Caps (if paper wax types)
Pots (mechanical failure of wiper to make good contact due to dirt and corrosion)
Resistors (mainly drift high but there are wide differences in the amount tolerance that can be allowed depending on the circuit)
Can eletros, this is subject for a lot of debate, but I think it has a lot to due with the manufacturer, environmental conditions and how the set is used.

Dipped caps are often perfectly fine, but there are some that can cause trouble.

Last edited by DaveWM; 07-19-2016 at 08:54 PM.
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Old 07-19-2016, 09:03 PM
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miniman82 miniman82 is offline
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I didn't see it in person before the recap, so I can't comment on what state the tuner was in at that point. I can only say what I saw when it was running at my place, seemed like a lack of signal strength to me. Could be bad diodes, I don't remember if we tried injecting a composite signal but I think so. Honestly I would need more diagnostic time with it if I were going to go any deeper, if Jeff is willing to leave it at my place for a while, I can take another look at it and post up what I find. But I suspect the tuner is shot internally somehow, or there's something messed up with the IF strip.
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Old 07-19-2016, 09:40 PM
Philco123 Philco123 is offline
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Thanks Nick and Dave for all the vintage TV counsel and words of wisdom. I will replace the cap on the IF board (now on order) and the detector diodes (using proper heat sinks this time) and report back with my findings. Thanks again for the assist !
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Old 07-19-2016, 10:46 PM
DaveWM DaveWM is online now
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Glad to help. You will get it going just takes some time. Be sure to check those old ones out and against the new ones. That's just a guess on my part, like I mentioned in the video, lift one leg and see how it test.

Nick do you have a tuner subber?
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  #14  
Old 07-20-2016, 06:43 PM
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miniman82 miniman82 is offline
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I have many different flavor of pattern gen here, I can go through the tuner, IF, first video tube, whatever.
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