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incova
Joined: 27 Nov 2006
Posts: 789
Location: london
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| Posted: Sat Jan 28, 2012 3:20 am Post subject: Hi Guys,difference between 4 and 6 pole astigmatism magnets? |
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Can anyone tell me what the main differences are. I am trying to do astig on my 4600 and getting my brain mashed up.
I assumed the magnet in the middle is the 4 pole magnet used to centre the beam and the one nearest to the focus assembly is for dot shape? So the magnets next to the crt cart would be to refine the beam centering magnet. Is this correct as at the moment I have found that my magnet nearest to the lens is the one that centres the beam best when I twist the handle. I have actually got the green into a position where it is a good dot and does not move even when ramping up focus up and down but I think this was a fluke as I cannot really see the vertical lines when defocusing the tubes. Anyway, any advice will help, I am going to use a extron VTG and see if that helps later on as Chip said that you get lima bean dots on the Ampro if you just use the internal test patterns. Wish me luck! 
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Curt Palme
CRT Tech
Joined: 08 Mar 2006
Posts: 24396
Location: Langley, BC
TV/Projector: All of them!
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| Posted: Sat Jan 28, 2012 3:34 am Post subject: |
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THE 2 pole magnet is the one that moves the raster around the most. THe 4 pole adjusts the shape of the dot from oval to round. THe 6 pole will help in correcting the roundness of the dots as well. This is seen most in NEC XGs where the 6 pole magnets help changing a triangular looking dot to a round one. NEC says to concentrate on the top of the image for that.
Also remember that contrast should be at 100% when doing astig to drive the tubes hard, and also keep in mind that some magnets can actually lose their magnetism.
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incova
Joined: 27 Nov 2006
Posts: 789
Location: london
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| Posted: Sat Jan 28, 2012 3:52 am Post subject: Thanks Curt |
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So my 2 pole magnet would be located near the lens end Curt then the 4 pole in the middle for beam focus and the 6 pole next to the crt card for fine shaping the dot, would this be correct?
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Curt Palme
CRT Tech
Joined: 08 Mar 2006
Posts: 24396
Location: Langley, BC
TV/Projector: All of them!
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| Posted: Sat Jan 28, 2012 3:59 am Post subject: |
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Sometimes they are reversed. Just check which one moves the raster the most, and that's the 2 pole.
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incova
Joined: 27 Nov 2006
Posts: 789
Location: london
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| Posted: Sat Jan 28, 2012 11:52 am Post subject: Thanks Curt |
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Will do, thanks.
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Tim in Phoenix
Joined: 21 Oct 2006
Posts: 4409
Location: Phoenix
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| Posted: Sun Jan 29, 2012 12:08 am Post subject: |
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Flare in front (2 pole)
Regular stig in rear (4 pole)
Triangular dot correction in middle (6 pole)
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incova
Joined: 27 Nov 2006
Posts: 789
Location: london
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| Posted: Sun Jan 29, 2012 1:32 am Post subject: Thanks Tim |
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Thanks Tim that makes sense now, I worked it out the hard way lol! not that I am getting very far with this astig!
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