Green convergence problem after tube swap

TheShanMan

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Sadly, the tv's rings in their original position didn't yield a converged image (don't know if the tv was poorly converged or if it has something to do with the tube swap, and yes, I marked the position of all the rings). So I've had to resort to the frustration known as convergence.

I've gotten the red/blue convergence pretty dialed in as you can see from the first pic (except the upper and lower right corners, but I imagine my magnetic strips will rectify that). However, the green on magenta convergence isn't going so well thus far. Converged in the center of the screen, but the entire top and bottom are out significantly. It seems odd to me that the whole center horizontal "band" is converged and the top and bottom "bands" are not.

I did a little searching and came across this post from the ever helpful modessitt in which he said sliding the rings forward or backward can help with convergence. That's what I plan to try next. But in the meantime I thought I'd throw my issue out there for any feedback. I have 2 questions.

First, obviously, is why am I having this trouble with the green and how do I solve it?

Second, what is the right spot to (theoretically) place the set of rings when sliding it onto the tube? The tv tube's rings were positioned quite a bit closer to the neck board than the arcade tube's rings. Looking at the 4600 manual, it appears that the tv tube's rings were placed in the wrong spot (but maybe it varies from tube to tube???). OTOH, if I place them in the spot that appears to be right (from the standpoint of this noob), there is very little room to move the yoke back to do the purity adjustment (centering the magenta band). So let's say you were handed a tube in one hand, and the rings in another. Where would you place the rings?

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Looks pretty close to what the 4600 manual says (which I was using), but I'll look it over in more detail. Put another way, why would the tv tube's rings be so much closer to the neck board (maybe 1/2" or so)?

Any ideas on the green convergence issue? Sliding the ring assembly back and forth did affect convergence, but it didn't seem to affect the vertical "stretching" problem I have on the green.
 
Is it possible that you put the rings on backwards? Also, are you using the rings that came off of the TV or the original monitor rings?
 
They're the rings from the TV. Wonder if I'd have better luck with the arcade monitor rings. I am sure they aren't on backwards though.
 
Yeah, the backwards thing was a shot in the dark since the spacing has moved so much.

Have you tried moving the yoke back and forth while powered on to see if there is another location that it looks right?
 
I suppose that's worth a try, but to be honest I can't even seem to get 100% color purity. Scoot it one direction and it gets worse in one spot (upper left), scoot it the other direction and it gets worse in another (right side). So I found the spot that gives me the best purity overall (small amount of impurity in both spots), and stuck it there. But certainly at this point anything is worth a try so screw the purity for the sake of experimentation. :)

Is it possible that it's a poor choice in tubes? It is a cr23 a48 so I figured it's good to go. Do I have to worry about yoke impedance given I kept the yoke with the chassis? I'm not too clear on that one.
 
Don't forget that the "pitch" of the yoke can create similar issues that you have.
Since you have it so close, leave it locked in place (don't slide it back and forth) and try a slight tweak of the yoke left/right or up/down. You may have to loosen a wedge to nudge it to see the effect. It may help some of that.

Convergence.....just gotta love it. It's a whole lotta fiddlin'.
 
I'm not sure if you guys are picking up on the exact problem. All the tweaking I've done with the rings and the yoke affect the relative position of the color grids and/or rotate the color grids. But this is a problem of the vertical size of the green grid being too large (as opposed to some/all of the edges being out). Horizontal size is fine. If there were such a thing as individual color v-size pots, my problem would be solved. If you look at the 2nd pic, divide the screen into 3 horizontal bars. The middle horizontal bar has great green convergence all the way from the left edge to the right. But the top bar is out equally from the left to the right (it's too high) and the bottom bar is out equally from the left to the right (too low).

I did go back and play more with the yoke, both up/down/left/right and in/out. Nothing seems to put a dent in this issue. :confused:

Can anything else cause this kind of effect, such as an issue on the chassis or neck board? Or a tube issue which could be addressed by my rejuvenator? Wouldn't hurt to check it out with my rejuvenator if no one has a better idea.
 
Well, as I expected the tube checked out as perfect with the rejuvenator. So I'm at a loss. Unless someone throws out a bright idea soon, I'm going to just consider the tube a bust and move on to another tube. This has been great as a learning experience, but extremely frustrating at the same time. I'm ready for a tube swap that goes very smoothly. :)
 
Yea, it can be time consuming and mess with your patients to do this part.

One thing you might want to check, since you used a different yoke than what was originally on the TV, is that there are no chevron magnets around the tube. Those were placed there for the original yoke and might be throwing off the beam with the current yoke.

I never get it 100% perfect, I just try to get purity and convergence to be as close to exact in the center of the tube and then use adjustment strips or chevrons on the outer edges to get it reasonable.

I have a pretty easy to follow adjustment sheet that Hawkeye picture tube gave me that is really simple and easy to follow if you want me to scan it and send it to you.
 
I'd love to get a copy of that sheet! No magnets on the tube (yet). However, I would normally expect the convergence to be the worst at the corners, a bit better at the middle edges, and then of course perfect in the center. That's not the case here though. I think this is beyond just needing magnets for that reason (though I could be wrong since I'm no expert at this). This seems quite a bit beyond "fine tuning" with magnets to me.
 
Here is a scan of one of the documents he gave me. He has a nice simple 1,2,3 approach to help keep the idea simple in your head.
 

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Here is a second document, it's basically the same instructions as the first, but the images are a little bigger to show you the proper cross hatch pattern setup.
 

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I was doing #2 and #3 in reverse order, so it'll be interesting to see if that makes it any easier. Thanks for scanning and posting. Nice quick reference pages! :)
 
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