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  #31  
Old 02-17-2017, 09:15 AM
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Yep, ringing in the horizontal yoke. Check the 56pF cap or 1K resistor hidden in the yoke.
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  #32  
Old 02-17-2017, 09:49 AM
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To avoid a possible wild goose chase, it might be worthwhile to ascertain that the bars are deflection-based, and not in the video chain. Shunt the CRT control grid to ground with a cap, which kills the video. If the bars are unaffected, they are in the deflection system. Cap value not critical, anywhere from .047 - .1 or so.
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  #33  
Old 02-17-2017, 10:30 AM
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Originally Posted by vts1134 View Post
Since this is the second time that's been mentioned, I trust my method for restuffing is such that most can't tell that I've done anything (which is half of the goal in a restoration).
What! You mean you didn't wipe all that crusty old wax off so they look like shinny NOS? How dare you.
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  #34  
Old 02-17-2017, 02:42 PM
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Originally Posted by bandersen View Post
Yep, ringing in the horizontal yoke. Check the 56pF cap or 1K resistor hidden in the yoke.
Could either of those parts also be the cause of my raster being off-center to the left and my horizontal centering control being pretty much non-functioning?


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Originally Posted by old_coot88 View Post
To avoid a possible wild goose chase, it might be worthwhile to ascertain that the bars are deflection-based, and not in the video chain. Shunt the CRT control grid to ground with a cap, which kills the video. If the bars are unaffected, they are in the deflection system. Cap value not critical, anywhere from .047 - .1 or so.
I'll give that a try tonight.
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  #35  
Old 02-17-2017, 03:28 PM
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Could either of those parts also be the cause of my raster being off-center to the left and my horizontal centering control being pretty much non-functioning?
I don't think so. The centering control works by adjusting a DC bias current through the horizontal yoke winding. Check the voltage across the centering control and see if the voltage on the wiper changes as you adjust it.
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  #36  
Old 02-19-2017, 07:21 PM
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Progress report. The horizontal centering control is broken. It stops at around 10ohm and it's supposed to be a 20 ohm control. Does anyone have a 20ohm control w/center tap and a short thumb screw shaft?



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  #37  
Old 02-19-2017, 07:32 PM
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Might be able to jump a 20 Ohm across it's terminals for a temp patch.
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  #38  
Old 02-19-2017, 08:01 PM
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Regarding the horizontal ringing, after shunting the crt control grid to ground to confirm the issue was not in the video, I replaced the 56pf capacitor in the yoke and while the black bars didn't completely disappear, they seemed to be less noticeable. Is it possible the cause can be coming from more than one place?

I also replaced the 6SN7 in the vertical oscillator and the vertical collapse didn't return after that. I'm going to keep an eye on it though as it went away and returned before.
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  #39  
Old 02-19-2017, 08:40 PM
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stuff can work together to make horizontal ringing.
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  #40  
Old 02-20-2017, 12:40 AM
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Originally Posted by vts1134 View Post
I'll take that as a very nice compliment. All of those capacitors are retuffed original shells. Since this is the second time that's been mentioned, I trust my method for restuffing is such that most can't tell that I've done anything (which is half of the goal in a restoration). The only modern capacitors that are visible in the set are the ones associated with the video amplifier/inverter that I added. I figured since that is a modern addition then it should have visible modern capacitors.
Nice!
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  #41  
Old 02-27-2017, 10:25 AM
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Progress! I found that the problem with the horizontal centering was not due to a bad control pot. The issue was with a two section capacitor that I mistook for a single section. I had been shorting out C207 to C208 which shorted the upper half of the wiper. I rebuilt the capacitor again with both 100uf caps in place and the horizontal centering now works as expected. This repair also allowed me to adjust the focus coil for its intended purpose of uniform focus instead of adjusting it to center the raster. Now I have a centered, fairly well focused image .

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  #42  
Old 02-27-2017, 10:32 AM
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I'm going to swap the original 10FP4 back into the set (if you'll remember it was brighter and had more contrast, but didn't focus as well) to see how that one looks now that I can move the focus coil more freely. I also need to find vintage replacement 56pf and 82pf capacitors. I have modern replacements in the set in these values and they will need to be swapped out. Anyone have good, but old, replacements for those caps? I also would like to see if adding a vertical retrace blanking circuit is feesable for this set. I have read about this modification, but only on sets where the video is fed to the cathode, not to the grid like this set is. Does anyone know if you can do a retrace blanking mod on sets with video fed to the grid?
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  #43  
Old 03-18-2017, 09:12 AM
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Making slow progress. I'm pretty much down to one remaining problem. There are diagonal lines in the video that I suspect are caused by my video circuit. Phil is also working on a video inverter circuit for his set, but didn't mention the same issue, perhaps it's unique to my set. The lines are more noticeable on brighter scenes and are extremely difficult to film. Luckily while watching Daniel Tiger with my daughter this morning I found the perfect scene to show the problem. See video here https://youtu.be/QpJ0pEOIjN8. Anyone have any thoughts?
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  #44  
Old 03-18-2017, 10:12 AM
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Those look like artifacts of the color sub carrier. Your best bet would be to not drive it with the yellow composite video output of your source, but instead use the green component output or the monochrome half of the S-video output...That will give you video free from color sub carrier.
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  #45  
Old 03-18-2017, 01:44 PM
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Those look like artifacts of the color sub carrier. Your best bet would be to not drive it with the yellow composite video output of your source, but instead use the green component output or the monochrome half of the S-video output...That will give you video free from color sub carrier.
No such luck, I'm already using Y only on a component video cable. That does make me think I need to try another video source though.
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