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#1
12-14-2007, 04:08 PM
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'50 RCA KCS-47A Question
I've got 4 or 5 shaded bands down the left side of my picture. Always there but best seen with signal. What is the cause and how do I get rid of them? CRT is a 16bp4 tests good.
Tnx Terry 
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#3
12-14-2007, 08:25 PM
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I don't know either, I have a couple sets that do this to one degree or another.
From what I've read I believe the problem in in the damper circuit somewhere. Assuming you've already recapped this set?
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#5
12-14-2007, 10:20 PM
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If the drive has no effect and the damper is good, the yoke is usually to blame. You probably have an open or shorted capacitor in the yoke.
I think the technical name for this symptom is ringing. If i can find my service notes I may have some troubleshooting points for you to look at.
__________________
Jordan
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#6
12-15-2007, 12:06 AM
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Quote:
Someone mentioned a cap in the yoke. Thats a new one on me.  I knew that there were a few resistors in a lot of yokes but wasnt aware of caps. Admittedly I have only popped the cover off of a few...
__________________
"Face piles of trials with smiles, for it riles them to believe that you perceive the web they weave, and keep on thinking free"
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#8
12-15-2007, 07:39 AM
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I think the dark picture is just the camera. It's good in daylight and easy to watch. The set has been recapped and some resistors have been replaced. I did adjust both slugs (top and bottom) on the horiz. osc transformer to bring the horiz. frequencey in to range when I first got it working. I don't know if there is a balance between those two adjustment? I set the top slug in the middle and adjusted the bottom till the picture would lock in. I'll sniff around the damper and see if I can find anything thing.
Tnx Terry
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#9
12-15-2007, 11:00 AM
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Those pics are a bit better.
Hm, do the lines change at all? Do they look the same regardless of whether or not there's a signal? In both of your pics, the lines themselves look the same regardles of what picture is on the screen.
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#10
12-15-2007, 11:17 AM
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I'm pretty sure its a yoke network problem.
Terry: THe transformer can has two functions, phase and oscillator frequency. THe part of the transformer that's available to adjust on the back panel is the secondary of the transformer. It controls the oscillator frequency (horizontal hold) The primary of the transformer that adjusts from the under side of or underneath the chassis is for the horizontal phasing. Usually the generic way to adjust it (the sams will tell you) is to pull the hoirz afc tube and adjust the oscillator so that instead of tearing the lines stand upright. Then you adjust the phase so that you can make the picture stand still as possible. When the tube goes back in everything should lock into place. However, being that your picture looks good apart from the ringing I would leave it be.
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Jordan
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#11
12-15-2007, 11:26 AM
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I'll go with Jordan's idea, but if correct, the Horizontal Drive control should make changes you can see in those bars (make them worse and better.) That could then be one of the small disc caps in the rear of the yoke (if that set has them), or other horizontal sweep issues. But it isn't a bad yoke, if I had my guess at it.
If it's not changed in appearance by moving the drive control, then I'd go with a leaky cap someplace, particularly in the video circuit. If that's it, you should see the bars as a foreign waveform if you scope the B+ to the video circuits. Charles
__________________
Collecting & restoring TVs in Los Angeles since age 10
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#12
12-15-2007, 12:49 PM
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The bars don't change just easier to see with no video. There's some disortion in the picture as it pass the bars. This set use a trimmer cap to adjust the drive. I'll give that a shot.
Terry
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#14
12-15-2007, 01:51 PM
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Pretty sure they have been there since I started on this project
Terry
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#15
12-15-2007, 05:03 PM
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Hey Terry, is there a lengthening or shortening of the image where the bars are? If this is a sweep-waveform problem, it would explain why the tube is darker in places, since a faster trace would cause less electrons to hit the phosphor, and would thus appear darker. My Fairfield had some minor distortion on the left side, but it didn't produce those dark bars.
Did you replace that nasty .01 cap across the H-waveform coil terminals? I can't remember if it was you or someone else who brought the subject up a while back. Anyway, my money is on the waveform adjustment slug in the H-osc can, don't remember for sure, but I think it's the bottom one... Last edited by Einar72; 12-15-2007 at 05:04 PM. Reason: goof
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