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Discussion Starter · #1 ·
I have a question about the astigmation and centering magnets. I've been going through the procedure authored by Tinman on my 6pg xtra. I did the green and red alright. I'm not completely satisfied with the astigmation that I was able to achieve, but I will continue to work with them. The question I have is with the blue tube. The first thing I noticed was that the front ring pair, which was the astigmation on both the red and green, was the centering magnets on the blue. The rear pair was the astigmation, or shape, pair on the blue whereas the rear rings were the centering magnets on the red and green tube. Is it normal for the rings to be reversed among the tubes?


The second is a problem that developed after working with the blue for a little bit. The centering magnets stopped affecting the test pattern when they initially were working. The pattern would not move as I moved the rings. The result was that I could not readjust the test pattern to the other two tubes. So now the blue is off. The question is, what might have happened with the blue tube?


Thanks,

Tim
 

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Sound like someone may have retubed the pj and put the rings on backwards for the blue.


Not hard to do.....ask me how I know this.....


When it's backwards the rings do nothing/strange things, just like you describe.

To fix it you will have to remove the screws holding the big crossbar over the tubes, and reinsert them in the slots at the side, then slide the crossbar up.


Remove black tube tie rods for blue.


Loosen neckboard clamp.


Slightly lift tube and move forwards, while working the neckboard off. BE PARANOID ABOUT BENDING THE TUBE'S PINS.


Get the neckboard off, and then move the tube forward a touch and get the astig magnets off. Flip them over and put them back - they should line up naturally with dints in the cloth tape, or space them the same as the Red/Green - the distance does matter.


Put it all back together.


Just for the record, the rear magnet pair is the 2-pole (beam centre) magnets, then the 4-pole (spot shape) magnets. The brass rings/tabs behind the deflection coil are the raster centering magnets/rings - not quite the same thing.


Good luck


Mark
 

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Discussion Starter · #3 ·
Thanks, Mark!


I assume the four pole magnet has four tabs while the two pole magnet has two? If so, then the magnets on the blue are in the same arrangement as the red and blue.
 

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No, they have the same number of tabs from memory - look to see if the screw clamp on the magnet cluster is on the other side on the blue tube compared to the others - I think it's supposed to be on the neckboard side, but I could have that backwards (I'm at work, I can't check it till tonight).
 

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Discussion Starter · #5 ·
I'm not sure what clamp I am supposed to be looking at, but the black thumbscrew is on the same side as for the red and green, and then the screw for the clamp on the other side of the rings is also on the same side as for the red and green.


On all three tubes, the rear pair are the four tab rings, which you say are the spot shape magnets, and the front pair (closest to the bell) are the two tab rings, which you say are the spot center magnets. It was the two tab rings on the blue that were not affecting the test pattern.
 

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Ok, maybe everything is assembled correctly, and there's just some confusion about what's what.


I have attached a labled image - should help make things clear.


The clamp I mean is the astig magnet clamp, it should be at the rear of the astig magnet cluster. NOT the black clamps - they are focus and deflection coil clamps- nothing to do with astig.


Just make sure it all looks like the picture.


The astig magnets work in pairs - you rotate the pair together to change the direction they work in, and rotate the pair relative to each other to change the strength.


2 pole = electron beam centering in the electron gun(not raster centering, although it will also affect raster centering).


4 pole = shape of the beam, aka spot shape, roundness.


Mark
 

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Well, now I'm at work and will have to wait until I get home before I can compare your picture to my pj.


The clamp I referred to earlier looks to be what you have labeled as the neckboard clamp and the black thumbscrew is what you have labeled as the focus coil clamp. I assume the screw clamp you were referring to earlier is the astig magnet clamp. I did not look at the astig magnet clamp.
 
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