Or maybe not. The no-signal condition persists, as if there's nothing coming out of the tuner. I found that I can connect everything if I stand the chassis on our trusty old cooler. Not convenient, but I'm lacking a workshop at the moment.

http://antiqueradio.org/art/RCACTC-4LameSetup.jpg

Injecting a video signal at the video amp gives me a faint picture.

http://antiqueradio.org/art/RCACTC-4FirstCrossHatch.jpg

Injecting an IF signal in the IF strip also gives a (fainter) picture.

http://antiqueradio.org/art/RCACTC-4...estPattern.jpg

Subbing the 6X8 and 6BQ7 tubes in the tuner changes nothing. I still get absolutely nothing from the tuner -- no static/scratching when you change channels, nada.

I guess the next step is to pull the tuner and try some cleaning. I'm still at a loss to see why the signal suddenly disappeared. There are no obviously torn-loose wires, etc.

I posted the Sams manual here for anyone who's curious:

http://antiqueradio.org/art/RCA-CTC4-Sams-314-9.pdf

I believe the schematic from my RCA field service manual is more accurate, but I don't have a scan of that.

Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html

Try wiggling the IF and AGC tubes, and adjusting the AGC control. Part of the reason I shelved mine mid-resto (asside form it needing and alignment that I'm not equipped for or experienced at) was that the IF sockets in mine were intermittent and so was the AGC...I could loose all signal if it was in a bad mood on a given day.

Wiggling every tube in sight got me nowhere, but after cranking up the AGC control I'm getting a healthy scratch (visual & audible) when I change channels. Maybe cleaning the tuner will help. I don't see any easy snap-off panel that can be removed. I guess you need to unsolder the connections and remove the whole tuner assembly.

Phil Nelson

P.S. I did go through my usual routine of cleaning all tube pins & sockets at the start of this project. I suppose it can't hurt to re-clean the sockets in the tuner & IF, etc.

IIRC I was able to clean my tuner without electrically disconnecting it, but it has been about 3 years since I did that....I think a number of screws have to be removed to get the cover off.

Sockets were the culprit in mine as well, so that makes 3. I also had an AGC pot that was smoked, that sure didn't help. I'm still trying to get my audio back, I lost it at some point and it's been on vacation ever since.

To fix the sockets, you can sort of repin them with new contacts from another socket. You have to be careful and do them one at a time in situ, but when you're done the job is worth it not to have bum connections on the PC boards.

What type of sockets did you get the new pins from?

I'll have to test the AGC pot when I get back around to my CTC-4.

Vigorous socket re-cleaning changed nothing. Next stop, Tunerville.

http://antiqueradio.org/art/RCACTC-4...verRemoved.jpg

Removal meant unsoldering ten connections, but they were all easily accessible. I will carefully clean the contacts with swabs and liquid DeOxit.

Phil Nelson

If the video amp is after the tuner, signal path wise, why would a weak picture(while injecting at the control grid of the video amp) mean that the tuner was bad? Not saying it isn't, I'm just not following the sequence of events I guess. :scratch2:

I was just walking backward, doing a very basic check to see what sections could pass a signal. Seeing a picture when I injected video at the video amp suggested that things downstream from there were working (at least marginally). Seeing a picture when I injected an IF signal at the IF amp suggested that things downstream from there were working. So, the no-signal problem was likely between the antenna terminal and the IF strip.

The solution was simple, after all, and it turned up when I serviced the tuner. The UHF-VHF switch in back of the tuner was funky and it had stuck in the UHF position. Here is the switch working normally:

http://antiqueradio.org/art/RCACTC-4...chAnimated.gif

I'm not impressed with that switch, or the quality of the tuner in general, but it's all clean and operational now, and I can get a picture through the antenna input.

http://antiqueradio.org/art/RCACTC-4TunerCleaned.jpg

And now for that Wizard of Oz photo you've been waiting for!

http://antiqueradio.org/art/RCACTC-4FirstWizardofOz.jpg

Yah, we're a long way from a good color picture, but the CRT transplant was successful, knock on wood, and I think there's hope for the old girl, after all. Now to read up on CTC-4 setup procedures . . . .

Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html

Looks like they could have done a little more work on the design of that switch....
Movement to the right those contacts hardly get anything to stand on....

Anyway, nice job on the animated gif....

Have you not degaussed the tube yet? or not done any purity? <-- Sorry re-read above posts...

Nice bright tube though....

If you come across an original tube, will you put it back in...?

Hi Phil, thanks for your patient reply to my video amp question, and sorry for the "senior moment" on my part.

Ditto on the "nice job with the animation", and with the super job cleaning that UHF switch. Seems really odd that RCA wouldn't have spent just a tad more on it given the expense of a color set in those days.

That wicked witch is looking badder all the time. LOL.

Well, I'm making slow progress. The B/W picture is very watchable -- good contrast, brightness, focus, geometry. I worked through the purity drill and all seemed well. Got nice clean red, blue, and green rasters. Those big magnets in the field neutralizing ring are pretty fun to use and they work well. I made the convergence decent in the central zone. It's not so hot around the edges, but there will be more time to play with all those dynamic convergence controls later.

When I display color bars or play a DVD, there is basically no color, even with the killer threshold turned all the way down and the color control turned all the way up. The AGC control seems to operate as it should. I tried tweaking the oscillator on one channel and convinced myself that fine tuning is not the issue.

Tomorrow is another day. I guess I will start at the color takeoff (chroma bandpass amp) and start working downstream, looking for problems in the color path.

As for using a 21AXP22, you bet I'd use one if I found one. I'd drive a 1955 Corvette if I found one of those, too, but meanwhile, we make do with what's on hand :)

Regards,

Phil Nelson

Since you will be working at this for awhile I decided to send you something to help aid in servicing your chassis
:)

Good luck on the convergence Phil, I got mine watchable and left it.

A bottle of Valium?

Convergence isn't so much an issue as the absence of color. I could see colored dots on the screen when doing static convergence, and see colored rasters when doing purity, but now it's basically black and white except for color fringing in the edge areas with bad convergence.

I have had to pack the whole thing away for a while. Having this project spread all over the kitchen was [A] not an efficient way to work and [B] giving us both a nervous breakdown.

Phil Nelson

These things can really beat a person up trying to find problems.
I know how that is.
make a short Extension for the Yoke for now, parcel post to Washington is about 4 days.
I remember this chassis from a few years ago when I owned one.
the Kitchen is the best place to work on !

This TV languished for a long time while my shop was torn up for remodeling, but now I'm running out of excuses and should get back to it. Perhaps I'll start with purity and work through the color setup procedures. After I gave it a 21FJP22A transplant, I left the purity magnets cranked all the way out, and the purity is about as bad as it can get.

Which reminds me: I got a copy of the big 91-page CTC-4 RCA service clinic manual from the ETF and scanned it. I figure ETF will put it in their schematic archive, but you can also download it from this URL:

http://antiqueradio.org/art/RCA%20CT...e%20Manual.pdf

The manual has schematics for early & late production, plus lots of other goodies.

Regards,

Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html

What an awesome document to make available!

Thank you for posting that service manual, Phil. One day I will proceed with my own CTC-4, after the kitchen remodel in progress now.

Back to the TV, I just worked through the preliminary purity & convergence adjustments, and saw plenty of R-G-B in the raster, dot, and crosshatch test patterns. No surprises. Then I switched to a color bar pattern and saw . . . shades of gray.

Same monochrome result if I play a DVD or receive a broadcast on rabbit ears from the in-house modulator. I adjusted obvious things like the color control, color killer & noise inverter, AGC, and so on. I also tested the obvious tubes, which are all fine.

When I use the fine tuner, it's as if the tuner is not centered on the frequency. Turning fully counterclockwise, you eventually lose the signal, as you'd expect. Midway in the fine-tuning range, picture is fine (although monochrome) and audio is absent. Cranked all the way clockwise, you can just begin to receive audio, the picture is still fine, and there's still a monochrome picture.

It feels like the frequency center -- where color and audio pop in -- is just beyond that far range of the fine tuner. This is the same on every channel.

I'm used to tuners where you remove the knobs and adjust an individual oscillator slug (for the selected channel) through a little hole. This tuner appears to be built that way, but I'll be darned if I can find the magic hole. The manuals that I have don't mention the oscillator slugs except in the context of a full-bore tuner alignment, which I'm not equipped to do.

If I'm missing something obvious, or barking up the wrong tree, please tell me now :)

Phil Nelson

It may need an alignment of some degree. I stopped working on mine due to RF/IF/AGC intermittents, and more so the glaring issue that I could fine tune monochrome, color, and sound, but not more than one properly at the same time.

You may be right. I tried tweaking the sound IF to move it into the "good mono picture" zone. I had to crank the adjuster all the way to the end of its range to get an improvement.

Maybe I'll push this one back against the wall for now. If I want to collect the gear & expertise to do an alignment, I'd rather practice on a B/W that already works well, rather than this guy.

It's frustrating when the colors show up well in test patterns, but not otherwise.

Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html

http://antiqueradio.org/art/RCACTC-4RedPurity.jpg

http://antiqueradio.org/art/RCACTC-4BluePurity.jpg

http://antiqueradio.org/art/RCACTC-4GreenPurity.jpg

http://antiqueradio.org/art/RCACTC-4Convergence.jpg

http://antiqueradio.org/art/RCACTC-4ColorlessImage.jpg

You don't need a full alignment. You just have to find those magic
holes. My Sam's says they are there. You need not fear adjusting
just the oscillator frequencies ... its absolutely the easiest
thing to get set in the tuner.

I guess there is nothing to lose by trying to adjust the oscillator slugs. I will need to make a new tool. In the process of packing up & unpacking my workshop, I misplaced (!) my special screwdriver with a whittled-down handle. I have a big pile of plastic alignment tools, but none of them is right for this job.

Phil Nelson

Adjusting the oscillator doesn't seem to be the magic bullet. I made a tool and used a tiny penlight to confirm that there is an accessible slug at the end of the tunnel labeled 12. After a little turning, now I can break up the video and audio at either end of the fine tuning range for that channel. The audio is outstanding near the clockwise end of the range, just before the picture breaks up. Still no color where you'd expect it, though.

Phil Nelson

IIRC on mine there is a point where the monochrome is really sharp. On one side of that point mono is blurry, but the audio is really clear, and on the other side if tuned to the ragged edge of the mono, and after sound is lost color comes in....Granted on mine some clod knocked one of the IF cans off the video board and I had to cobble it back on so god only knows what that did to mines alignment.

It is frequently said that these old sets don't really need realignment.
I've found that untrue. All my sets ... Pilot TV37, RCA 9-T-249, Emerson 610
and RCA CT-100 had abysmal alignment. True, many of the very sharp
trap frequencies were spot on, but the overall IF shape was in
every case completely wrong. Many RF channels were off too.

Its a lot harder to recognize on a B&W set, especially a narrow band
one like the TV-37. My opinion is that the best test on a B&W set
is the standard 100% color bars pattern (WYCGMRB). If alignment is spot on
you should have no problems with the relative brightness of the
bars versus fine tuning as you tune so the video carrier rides up from the
1/2 point to the 100% point. If its off, you will notice
problems. You can use 75% bars but 100% is a much better test.
This is what I fought with a long time on my CT-100.

I don't really know about other chassis, except that most of my older sets look maybe just OK, but my CTC-4 luminance section probably couldn't be more "sharp", or provide a more excellent picture. Chroma is also very good, but narrow band, as most know. Perhaps just a lucky circumstance, or maybe an extra measure of diligence to provide decent pics to encourage sales.
My 4 also has a correct gamut CRT, before the "gray screen" tubes. Best viewed in a totally dark basement LOL. :yes:
Kevin

My CTC-4 produced one of the most detailed, sharpest monochrome pictures of any vintage set I've owned when fine tuned for best best monochrome picture...

Before I cry Uncle and throw a tarp over this TV, I scoped the input of the first video amp to see what is getting through the video IF section.

My pattern generator is set to color bars, which the TV displays as gray bars.

http://antiqueradio.org/art/RCACTC-4ColorlessBars.jpg

The top scope trace is the TV's video IF output. The bottom trace is direct from my pattern generator.

http://antiqueradio.org/art/RCACTC-4VideoIFOutput.jpg

The signal looks pretty scrawny by the time it gets through the video IF chain; the burst signal is basically missing in action. Tell me if I'm wrong, but I'm taking this as a sign that the TV really does need realignment.

Phil Nelson

Try injecting a composite signal to the 1st video amp, if you haven't already. That would eliminate the IF as a fault area. If that's not it, it's likely a mistuned trap somewhere.

Hmm, results inconclusive. I pulled the 3rd video IF tube and injected video from my little Leader pattern generator at the grid of the 1st video amp. The picture had extremely weak sync and it showed a faint image.

http://antiqueradio.org/art/RCACTC-4InjectingVideo.jpg

Then I looked at the CTC-4 schematic and noticed that the 1st video amp is expecting +2.7V on its grid. That pattern generator certainly doesn't provide a signal that strong.

I tried using my B&K TV analyst as the video source. Cranking its video output control to the max gave me something over 2V, but still not enough sync for a stable picture. Still no true color, either, but if the signal is too weak to pass a usable color burst, I'm not sure what that proves.

Phil Nelson

I think I left the IF tubes in when I did it, but it's been so long now I can't remember. You put the signal right in to pin 2 or the 6CL6 and chassis ground, right? If it's not getting a picture, you may have a bad AGC pot on your hands. Mine was completely trashed when I first got the set, wouldn't display much of anything. Check to make sure it's responding, then move on to scoping the signal you're injecting at the CRT cathodes. If it's not coming through, there's still some issue somewhere. My set definitely works when injecting composite.

Some vintage color TVs had a separate detector diode for the chroma, separate from the regular video detector. Your oscilloscope display of the luma video would be typical found at the regular video detector of such a set.

Yes, that trace does look more like a luma-only stairstep pattern, but this set only has the one detector diode.

Yup, signal to pin 2 (or 9) of the 6CL6 and ground to chassis. I re-cleaned the AGC pot and made some cursory measurements that seem to indicate it's OK. Let's hope it is not junk. It is mounted concentric with the 2.5-meg noise threshold pot, and I don't know where you would get a replacement dual 500K/2.5-meg pot nowadays. Worst case, you could drill a new hole and mount a new pot separately, but . . . .

I put the chassis up on the workbench and plugged in the yoke & convergence assembly so that I can do some more systematic voltage & resistance checks, and look at things more easily with a scope.

Phil Nelson

I don't think the chroma could be completely missing, it's likely very attenuated after passing though the IF. I'd bet if you used the scope to zoom in on one of the luma bars, you'd still see a bit of 3.58 modulated on them. That's why there's a band pass amp, to bring the 3.58 back up to the point where it can be processed in the set. Same principle as attenuating sound before it messes with the video, then amplifying it in the audio section in intercarrier sets. Does your pattern gen have a means of switching off the chroma when bars are on screen? If so you can probe the band pass amp or demod driver to see if the chroma signal is getting though, switching chroma on and off while you probe gives you a way to make sure you're not just looking at noise. If it isn't getting through, you're probably looking at a slope adjustment to the IF at the very least because the 3.58 has likely slid off to one side and is not being seen by the set anymore. If the chroma is still there, it's likely the color AFC needs attention. You were able to get solid color raster before, but that is a very strong signal and is easy to lock onto. A weaker scene type signal might be throwing it off, so see if doing the zero-beat procedure does anything to improve it. I don't have many more ideas, besides a full on alignment. You could mail me your chassis I guess, I have the rig to do it...

Hmm, that's a tempting offer.

Meanwhile, I am checking things around the 6U8 AGC/burst keyer.

Phil Nelson

This is it right here.... Replacing every cap means all tuned circuits need re-alignment.
Chances are each tuned circuit has moved it's center up or down, and as
a unit, is just rolling off before the chroma part and attenuating it..... Easy
fix, but yes be sure everything else is ok....

.

Squirrel boy, Most of the caps we replace in sets like this are not in the IF tuned circuits (including the odd paper or two in the IF section of some sets).

Good idea. Yes, my generator has a Chroma Off switch, so that would be easy to do.

Gack. I was measuring something else when HV disappeared and the 6CB5 horizontal output tube began to red-plate :sigh:

I pulled the 6CB5 and it is toast. No spares for that in the house, so I'll have to order a replacement (or two, for good luck).

Meanwhile, I assume it's OK to power up the chassis on the workbench (with yoke and convergence coils connected) with that tube removed . . . .

Phil Nelson