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  #61  
Old 01-22-2011, 09:20 PM
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Quote:
Originally Posted by stromberg6 View Post
Mine has a very small purity problem in the lower right corner, and I think it might be due to the tube needing to be degaussed, but I'll try the magnet again.
I tried degaussing this one too, but the spot persists. It's pretty close to optimal, but there's still a tiny little area I can see where it's not right. It's a shame, because the tube checks as new on the tester. None of my other sets even needed the purity magnets, the screens are just perfect.

Quote:
BTW, I notice that your 4 also doesn't fill the screen all the time at the left side. Interesting; mine does the same thing. If I increase the line volts to 120 I can get a full pic. These things have notoriously poor voltage regulation, so maybe that's one of the problems. Don't want to screw around with the width circuit again yet.

I haven't yet messed with the width controls on this set, because the replacement centering pot's shaft is too short for the knob to fit on it. I think once I graft an extension on it and adjust horizontal width, the screen will look normal.
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  #62  
Old 01-22-2011, 09:56 PM
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Can you post a pic of the total CRT back magnetics? Does this set have the little hairpin-shaped purity poles on a tube mounting ring (around the CRT bell) like the CTC-7 mount I put in my -5 to accomodate the 21FJP22? Those hairpins do make a difference in uniformity of the purity.

If this chassis has the multiple magnets around the edge of the face, I'd suggest removing them when using a glass tube. They were necessary for the metal-bell tube, which strongly distorts the fields very near the edge, but their effect is probably too strong right at the edge of the glass tube and falls off too rapidly towards the center.
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  #63  
Old 01-23-2011, 01:48 PM
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No, it has a band with round magnets on it. I need to do the same thing you did on your 5, but I don't have a spare set of hardware to modify. My main issue is what to do with the yoke; it doesn't mount to the CRT neck, it's held by the large metal piece which also supports the CRT. Perhaps there's a way to use a later yoke with the pull up ring?
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  #64  
Old 01-23-2011, 02:04 PM
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Quote:
Originally Posted by miniman82 View Post
No, it has a band with round magnets on it. I need to do the same thing you did on your 5, but I don't have a spare set of hardware to modify. My main issue is what to do with the yoke; it doesn't mount to the CRT neck, it's held by the large metal piece which also supports the CRT. Perhaps there's a way to use a later yoke with the pull up ring?
Looks like you have the edge magnets screwed out towards minimum strength - I'd guess that's the best position. If the ones on the bottom aren't screwed out all the way, you might try that. Also, if you have a small refrigerator magnet, you could try moving it around the bell about halfway back to see what effect you get.

I'd try getting the purity with added magnets before changing the hardware. I had no choice on the -5 when I went to the glass tube.
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  #65  
Old 01-23-2011, 02:27 PM
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Yes, most of them are at min strength. The only ones I had to actually use were the ones at the bottom left side of the tube, and you're right, thye are a strong effect at first but it quickly diminishes at the center. I'll try an additional magnet farther back, sounds like a good idea.
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  #66  
Old 01-28-2011, 04:44 PM
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I noticed that the crosshatch pattern looks funky, anyone ever see something like this? It looks mostly fine, until the solid horizontal line passes through the vertical one right in the center. It's like the horizontal line causes some ringing in the video amp or something, see the squiggly vertical line? It also looks funny on the left side, something that was pointed out by a member on ARF. At first I didn't think anything of it, but there's clearly an issue there. See how the horizontal lines continue off screen, while the vertical line of brightness that stops near the edge?

I checked my other sets, and they don't do this. Think maybe it's because of all the inductors in this chassis? It does have 10 times the number of peaking coils than any other chassis I've worked on, but I'm inclined to believe it should still be able to display a simple cross without an issue. Thoughts?

Second shot is just more brightness than the first.
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  #67  
Old 01-28-2011, 07:03 PM
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looks like sync separator problem - white video causing the sync to be clipped at a different level. I also notice it occurs at the top, where the horizontal sync has been disturbed by vertical sync Do you have a multi-square crosshatch? Does the wiggle follow every horizontal white line?
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  #68  
Old 01-28-2011, 07:12 PM
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Also might try turning the noise threshold control to see if it affects this.
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  #69  
Old 01-28-2011, 08:09 PM
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I was thinking sync as well, but it's so darn stable! I can twist the horizontal control multiple times, and it stays locked. Vertical is pretty solid too, is it possible to have stable sync while still having an issue? Yes, it happens with the multiple chrosshatch too- at the intersection of every horizontal line, the vertical gets a little squiggle to it. Noise inverter and AGC have no effect on it.
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  #70  
Old 01-28-2011, 08:29 PM
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Well, now I'm just fishing, but have you checked component values in the horizontal oscillator/control section? Even if it's getting an input jolt it shouldn't get, I think it maybe should respond with a more damped response instead of a decaying oscillation.
The following three components are the main control loop filter:
C160 .01
R165 3900
C159 0.47

+ other R's and C's in the vicinity
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  #71  
Old 01-28-2011, 08:32 PM
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All the caps and resistors in the horizontal section are either new or within tolerence. I thought I was having a problem with the originals before, but it ended up being a power supply wiring glitch that was my fault. The power supply is fine now, and I strongly doubt issues with the oscilator.
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  #72  
Old 02-13-2011, 09:11 PM
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Thanks, Wayne!


In the end, you were right. When I initially set this thing up, it still had a miswired power supply with 60hz noise. That means I tuned the horizontal sine coil with that same noise in it, but I failed to recheck it after I corrected the problem. Looked at it with the scope the other day, and sure enough the first hump of the waveform was was lower than the second one! I watched the screen as I tweaked for equal humps, and sure enough that coil being detuned will cause the ringing I was seeing. Now I have nice straight lines on the screen, just like I should.
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  #73  
Old 02-13-2011, 09:25 PM
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I wasn't thinking of the sine coil, but it makes sense because it could affect the pulse shape going to the phase detector. Glad you found it!
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  #74  
Old 02-13-2011, 10:36 PM
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No matter, you got me looking into the horizontal section and that's what sparked my pot-frazzled memory.


OK, so at this point I did a very rough setup with the bar gen and reconnected the tuner. Still have some issues with a dirty AGC and color killer pot, those will be next on the clean/deoxit schedule. Here's the result, as seen via the Crapcast DVR!

Getting very close to a good picture now, all I have to do is another round of purity/convergece,
and nail the color alignment. What was that about keeping me off the streets for a while?
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  #75  
Old 02-14-2011, 11:40 PM
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Did work on red purity, and was able to just about cure that patch on the bottom of the screen and left hand side. Looks pretty good now, aside from a few little issues with red convergence in the bottom right corner. Can't really see it from normal viewing distance. I think I'm gonna call this a winnah for now, I'd like to enjoy it for a while before I send it off for refinishing. that will be the next problem, since all the people who work on wood around here are booked till the return of Christ. Any leads on someone who's free to do that kind of work?
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