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  #16  
Old 02-10-2016, 03:22 PM
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SwizzyMan SwizzyMan is offline
Restoring an admiral c322
 
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Maybe skipping the tuner and injecting a signal directly into the video amp and audio amp would improve performance? Also no pesky tuner alignments.
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Admiral C322C2 Regent (Restoring)
RCA CTC-7 Pensbury (Restored)
RCA CTC-5 Westcott (Restored)
CRA CTC--4 Director 21 (Restoring)
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  #17  
Old 02-10-2016, 05:20 PM
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Hagstar Hagstar is offline
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Originally Posted by SwizzyMan View Post
Maybe skipping the tuner and injecting a signal directly into the video amp and audio amp would improve performance? Also no pesky tuner alignments.
Actually, no. This requires creating an elaborate jig designed by RCA for this purpose. A 16 volt peak to peak signal with odd rolloff is required. One cannot inject ordinary video into a CTC4 by any means. Phil Nelson in fact is building such a pre-amplifier right now.

I'm not sure folks here are getting my issue is too much gain and adjusting the AGC. There is no more gain to be had most likely but
I talked about alignment as a check- I have no issues to solve I know about. But I know alignment can affect fine detail etc too.

John H.

Last edited by Hagstar; 02-10-2016 at 09:38 PM.
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  #18  
Old 02-11-2016, 12:15 AM
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Maybe it is just me. But I do not see the point of this hobby if we do not attempt to restore the set to perform as it did out of the factory. Case in point alignment: I taught myself the process of aligning a TV 50 years ago while in high school. In the late 60's I would find a late 40's set had seen then a lot of service which dictated an IF or tuner response check. It goes without saying what the needs are 50 years on.

In recent years, I have not found a vintage set which has not benefited from at least an IF response check. Every set I have had has always received a cursory IF sweep check even if the picture looked okay to begin with. After alignment I am always rewarded with a better picture, color and sound. Remember that even changing a vacuum tube in the IF strip can noticeably affect alignment.

Proper vintage tv alignment required only a modest investment in time and equipment.
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  #19  
Old 02-11-2016, 02:38 PM
old_coot88 old_coot88 is offline
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Back in the day, sweep alignment was not part of the routine service paradigm, and was largely neglected. Now that decades have gone by and LC components have (or may have) drifted a tad, sweep alignment is certainly worthwhile to learn to do. But practice on a B&W first.
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  #20  
Old 02-11-2016, 02:51 PM
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dtvmcdonald dtvmcdonald is offline
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Quote:
Originally Posted by Penthode View Post
Maybe it is just me....
In recent years, I have not found a vintage set which has not benefited from at least an IF response check. ... After alignment I am always rewarded with a better picture, color and sound.
I have seen only one old TV that was in what I would call acceptable "factory" IF alignment. Some were truly awful. The exception which was absolutely
perfect in every way, and would have generated a perfect color picture if the video was sent into a CT-100 was my oldest set: a 1939 TRK-12. But its IF is 8-12 MHz. The TRK12 on the other had some rather bad RF alignment channels;
it was not a production set tuner as it was apparently used to test conversion to the "intermediate set" channels.
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  #21  
Old 02-11-2016, 04:10 PM
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Originally Posted by Hagstar View Post
One cannot inject ordinary video into a CTC4
Well, yes and no. The required voltage is more in the neighborhood of 2+ volts, not 16 volts, but in any case, a "standard" video signal of approximately 1 volt may not work well in a CTC-4.

Fellow VKer ChrisW6ATV remembered that the Video Drive output from a Sencore VA62A can be set as high as 3 volts, and he got good results from injecting video from that device. (This essentially accomplished what I was trying to do by building a video preamp from the old RCA plans.) I tried that method, and confirmed that it works. More details in this other CTC-4 thread:

http://www.videokarma.org/showthread...259995&page=25

The Sencore VA62A has a rear jack to accept an external video source, so you can connect, say, your DVD player's video output there and use the VA62A to inject video to the CTC-4. Which is useful for diagnosis, but I doubt you'd want to use such a clumsy setup for everyday watching.

Phil Nelson
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  #22  
Old 02-11-2016, 06:56 PM
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Originally Posted by Phil Nelson View Post
Well, yes and no. The required voltage is more in the neighborhood of 2+ volts, not 16 volts,
BUT what about this?

"A signal amplitude of about 16 volts peak to peak sync negative is required for adequate contrast." This is on the schematic as well. All of the muddy low contrast video in my album I posted is from injecting conventional video.

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

John H.
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  #23  
Old 02-11-2016, 07:39 PM
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Originally Posted by old_coot88 View Post
Back in the day, sweep alignment was not part of the routine service paradigm, and was largely neglected. Now that decades have gone by and LC components have (or may have) drifted a tad, sweep alignment is certainly worthwhile to learn to do. But practice on a B&W first.
Looking at the service notes the process looks like several days of work involving lots of unsoldering, lots of resistors to be added and removed, dummy loads, bias voltage supplies with several kinds of bias. I did purchase a digital storage Tektronics 'scope so I can match those precise shapes given in the 'scope illustrations hopefully.

I sure will practice on a simpler set. Every service operation on the CTC-4 involves the possibility of damaging a simple put irreplaceable part. A small mistake and all the work and the set is down the drain. Unlike other folks I have no spares and frankly never see any.

John H.
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  #24  
Old 02-11-2016, 10:28 PM
old_coot88 old_coot88 is offline
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Jeepers, I sure don't remember anything near that involved. I did use a bias box initially, but found out you get the same results with or without it.
The hookup is purely intuitive and super simple (see attachment). Just tape a turn of wire around the mixer/osc tube as the injection point. Disable the LO by putting the channel selector on a hump between detents. And you're good to go, bias box optional (others' opinions may vary). The procedure is actually fun to do, and you can do it in a morning. Just keep the signal attenuated to the lowest level consistent with good response.
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File Type: jpg 2016-02-11-200326.jpg (23.7 KB, 18 views)
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  #25  
Old 02-11-2016, 10:47 PM
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Phil Nelson Phil Nelson is offline
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Originally Posted by Hagstar View Post
"A signal amplitude of about 16 volts peak to peak sync negative is required for adequate contrast." This is on the schematic as well.
Hmm, I don't know where they came up with 16 volts. Perhaps I'm looking at the wrong spot on the schematic, but at pin 2 (grid) of the 1st video amp (V110) the RCA schematic calls for +2.7V and Sams calls for +3V (+26V measured from the -23V source).

Phil Nelson
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  #26  
Old 02-12-2016, 03:29 PM
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Quote:
Originally Posted by Phil Nelson View Post
Hmm, I don't know where they came up with 16 volts. Perhaps I'm looking at the wrong spot on the schematic, but at pin 2 (grid) of the 1st video amp (V110) the RCA schematic calls for +2.7V and Sams calls for +3V (+26V measured from the -23V source).

Phil Nelson
I'm thinking I saw that on the 'scope diagrams BUT I might have mis-remembered thinking of this article instead, I had read it back in March after I got raster first time.

John H.
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  #27  
Old 02-12-2016, 03:33 PM
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Originally Posted by old_coot88 View Post
Jeepers, I sure don't remember anything near that involved. I did use a bias box initially, but found out you get the same results with or without it.
WELL that's encouraging, I will recap my Triplit sweep generator very soon then.

They also want you to disable horz. sweep though to remove the flyback derived reference pulse. THEN to compensate for the huge loss of load they show a bank of light bulbs in series or a honking resistor to serve as a dummy load lest the voltage go wild.

John H.
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  #28  
Old 02-12-2016, 04:12 PM
old_coot88 old_coot88 is offline
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'Oly ell Batman! Maybe get some second (and third) opinions on it then. I never had to disable anything other than the LO in the tuner (and don't know if that was really necessary). Or maybe the CTC-4 actually requires all this extraneous stuff. In any case, do a BW or two first.
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  #29  
Old 02-12-2016, 05:00 PM
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stromberg67 stromberg67 is offline
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Originally Posted by Hagstar View Post
WELL that's encouraging, I will recap my Triplit sweep generator very soon then.

They also want you to disable horz. sweep though to remove the flyback derived reference pulse. THEN to compensate for the huge loss of load they show a bank of light bulbs in series or a honking resistor to serve as a dummy load lest the voltage go wild.

John H.
Before I "fired up" the h-sweep in my CTC-4, I cobbled a couple of 100 watt resistors to the proper value and did voltage checks, etc. Worked out as the set came right up with raster upon full power up. Those resistors became super hot after a few minutes and could have roasted hot dogs suspended by strings above them.
Almost wish I had another CTC-4 to bring back to life.
Kevin
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