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  #46  
Old 04-11-2017, 07:33 AM
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Used the exact same matching transformer and cable on my CTC-11 and it looked fine. All my other TV's look fine this way too. Model C6030-13, Chassis 19CC19C.
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  #47  
Old 04-11-2017, 09:03 AM
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Given the jaggedness of the edge it looks to be on the edge of loosing sync...It all looks like symptoms of the AGC being set for too much gain and possibly mis-adjusted fine tuning.

If it were perfectly synced and fine tuning were set for optimal detail I'd ask you to put a meter on the focus line and run the control through it's range....If your set uses a focus divider off the 25KV HV line like my earlier 12B13C52 those will sometimes drift a bit...I solved mine by adding resistance on the correct side of the focus pot to bring it back into range...Drifted back out twice in a ~year then stabilized long term after the last adjustment.
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  #48  
Old 04-11-2017, 09:57 AM
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I'll try adjusting the AGC tonite.
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  #49  
Old 04-11-2017, 03:58 PM
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I turned the set on to adjust the AGC, and this time there was no raster at all. Just audio and a black screen with absolutely nothing on channel 3 and 16 from my modulator. Tuned to an unused channel, and there is nice brite snow. Turned on another TV to make sure there was input signal. I watched the set last night for a while (with a sucky picture), and it's not doing a goshdarn thing today.
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  #50  
Old 04-11-2017, 04:20 PM
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Update - Found my small screwdriver and adjusted AGC, and got my video back. Somehow it was WAY off. (???) However, I'm still having a problem with the vertical. I don't know if this is somehow related to the blanking interval? The horizontal lines are nice and crisp, but vertical lines are very noisy.
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Last edited by TUD1; 10-20-2017 at 11:05 AM.
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  #51  
Old 04-11-2017, 04:30 PM
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That looks like the color circuitry being driven off the monochrome bars (something you'll see on fine text or sometimes with miss-adjusted fine tuning). Some of my sets barely do it some others are terrible. I wish I knew exactly what causes it and how to fix it.
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  #52  
Old 04-11-2017, 04:51 PM
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This thing is just way screwed up. The NTSC test pattern looks *acceptable* but actual programming looks like pure trash. I've adjusted AGC, and I'm out of ideas. As you can see, the lines are not well defined at all, and it just looks very dull. Could a module be making a bad connection??? The test pattern looked WAY more crisp in my atelier last night.
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  #53  
Old 04-11-2017, 07:01 PM
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Adjust the AGC with it on the cable box. AGC setting can be wrong for some sources if adjusted using others.
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  #54  
Old 04-11-2017, 07:18 PM
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Did that. Made no difference.
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  #55  
Old 04-11-2017, 08:22 PM
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Possibly a plug-in transistor that's poorly seated.
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  #56  
Old 04-11-2017, 10:57 PM
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Took out every transistor, module, and tube one by one, and squirted Deoxit into every socket. After that, I got a very nice, sharp, vivid picture with well defined lines on the NTSC generator ONLY. After about ten minutes, the definition of the NTSC color bars went away, and it was just like it was earlier today with very poor definition. I was able to get a somewhat watchable picture on UHF 16, but VHF 3 still has contrast through the roof. AGC does nothing to compensate for too much contrast. Thinking either a bad electrolytic cap or transistor.
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  #57  
Old 04-12-2017, 12:17 AM
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Do you have a lot of electrical wires laying around? Try re-routing and bundling them, and unplugging any unnecessary ones. I've had electrical wiring cause weird intermittent problems that I spent weeks chasing. I moved one for an unrelated issue and presto, problem gone.
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  #58  
Old 04-12-2017, 08:31 AM
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There may be 2 AGC controls but I just dont remember.
One is RF AGC or AGC delay. Its the one I mentioned & only
changes the RF gain.
The other is for IF gain, look for it. It may not have both.
The IF strip also has a C-2 adjust pot. Its basically a video
output level.
You can try that too but since the set worked OK for a while
I am leaning tward small 'lytics now.

73 Zeno
LFOD !
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  #59  
Old 04-12-2017, 10:15 AM
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Last edited by andy; 11-18-2021 at 05:05 PM.
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  #60  
Old 04-12-2017, 10:27 AM
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+1 My 12B13C52 has only one module for color demod, color was intermittent (and eventually gray scale was shifting along with poking of the module). I re-flowed the lead on the the chassis contacts and the traces on the module and color has been rock solid since.

If you don't have the schematic for your set I probably do, and can take some pictures of the important areas.
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