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#91
03-03-2014, 10:36 PM
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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. 
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#92
03-03-2014, 11:54 PM
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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 Last edited by Phil Nelson; 03-04-2014 at 12:42 AM.
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#95
03-08-2014, 12:38 PM
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Quote:
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
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#96
03-08-2014, 05:49 PM
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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 !
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#97
02-23-2015, 08:56 PM
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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
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#98
02-23-2015, 10:43 PM
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What an awesome document to make available!
__________________
Tom C. Zenith: The quality stays in EVEN after the name falls off! What I want. --> http://www.videokarma.org/showpost.p...62&postcount=4
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#99
02-24-2015, 01:26 PM
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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.
__________________
Chris Quote from another forum: "(Antique TV collecting) always seemed to me to be a fringe hobby that only weirdos did."
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#100
02-25-2015, 01:45 AM
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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
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#101
02-25-2015, 02:50 AM
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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.
__________________
Tom C. Zenith: The quality stays in EVEN after the name falls off! What I want. --> http://www.videokarma.org/showpost.p...62&postcount=4
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#102
02-25-2015, 11:42 AM
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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     
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#103
02-25-2015, 11:49 AM
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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.
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#104
02-25-2015, 01:21 PM
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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
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#105
02-25-2015, 04:18 PM
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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
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