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Tips on adjusting 2 and 4 pole magnets????

 
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barco_75




Joined: 14 Jan 2009
Posts: 169
Location: Chicago


PostLink    Posted: Thu Nov 20, 2014 4:01 am    Post subject: Tips on adjusting 2 and 4 pole magnets???? Reply with quote


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I've finished installing my new Sony tubes in my converted 808---->808s . The one step that I always have trouble is adjusting the 2 and 4 pole magnets. I've attached the Barco reference guide. I can read the instructions but obtaining the results stated is not as easy.

I can get adjust the 2 pole magnets so the lines are roughly equal on each side (but not equal vertically and horizontally, i.e "b" does not equal "c", but "a"="b" and "c"="d") and the 4 pole seems somewhat circular. However, when I change the contrast, the dots and lines move for both 2 and 4 pole adjustments. Should they not move? With the two pole adjustment the width of the lines can vary greatly.

I remember Craig Rounds telling me to move the magnets so the image doesn't jump around before starting. Unfortunately, I don't remember what that means.

The instructions do not state the contrast and brightness setting when adjusting the 4 pole magnets. Should it be the same as when doing the 2 pole? Also, how much should you be twisting the 4 pole? It seems if you twist it too much, the 2 pole goes entirely out of calibration. When I adjust the 2 pole, with the Barco genlocked pattern (using pattern to match source frequency0, the center dot in the crosshatches is actually a small line which rotates. Does that mean anything?

I know the the dot is not round on the Barco and a bad reference but I was having trouble getting my AVHCD calibration software to boot on my Blu-ray. I've burnt a new copy so I can use that disk instead.

Adjustment of the magnets is limited because the 808S has amps restricting access.

Is there any decent instruction on how to do this and the results you should expect to see? Sorry for a million questions..but I have a million questions!! Help!!



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barco_75




Joined: 14 Jan 2009
Posts: 169
Location: Chicago


PostLink    Posted: Fri Nov 21, 2014 4:41 am    Post subject: Reply with quote

Ok, so I found Curt's astigmatism adjustments section. I've read it many times before but did quite get it. I also found guy kuo instructions. http://www.keohi.com/keohihdtv/experttips/guykuo/crt_astigmatism.html A video of the procedure would be the bomb!

The biggest issue I didn't realize is the 2 pole are the rearward magnets (knob) and the 4 pole are the front magnets (knob). I thought the 4 pole was done by twisting the tiny knobs and 2 pole was rotating the knobs around the neck. Now wonder I was so confused.

Anyway, I started by placing the two tabs for the 4 pole and 2 pole together and then rotated them 180 degrees. Then I adjusted the 2 pole with midpoint focus at 0 and then the 4 pole at midpoint focus at 100. I used the dots from the genlocked pattern since I couldn't find anything on the AVHCD calibration disk. The dots were not dots but more like Halos. I got them fairly round halo shape but couldn't get them exactly round.

I moved the center yolk and realigned my optical focus. With the increased sharpness it was much easier to find the sweet spot.
Picture is way better than ever before. So does this procedure seem correct? Is there any tips on making the astig even better?
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Nashou66




Joined: 12 Jan 2007
Posts: 16171
Location: West Seneca NY


PostLink    Posted: Fri Nov 21, 2014 4:45 am    Post subject: Reply with quote

If it looks better than you did a good job. there were some threads around here about the CPC magnets. Let me see if I can find links. Might not have the procedure but still interesting reads.

Nashou

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Nashou66




Joined: 12 Jan 2007
Posts: 16171
Location: West Seneca NY


PostLink    Posted: Fri Nov 21, 2014 5:27 am    Post subject: Reply with quote

http://www.curtpalme.com/forum//viewtopic.php?t=10647&highlight=magnets

http://www.curtpalme.com/forum/viewtopic.php?t=13702&highlight=astig+magnets

This has some nice pics of how the dots should look during at max and min focus.


http://www.curtpalme.com/forum/viewtopic.php?t=17749&highlight=astig+magnets

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redfox001




Joined: 16 Mar 2009
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PostLink    Posted: Fri Nov 21, 2014 12:48 pm    Post subject: Reply with quote

Thanks that first post makes clear to me how to nullify the rings before starting as there are two rings foor 2,4,6 poles. If you turn them exactly opposite they do nothing. In that case the whole ring assembly could be moved on the tube without anything moving. From that position on the adjustments should be done I guess.
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Nashou66




Joined: 12 Jan 2007
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Location: West Seneca NY


PostLink    Posted: Fri Nov 21, 2014 1:05 pm    Post subject: Reply with quote

redfox001 wrote:
Thanks that first post makes clear to me how to nullify the rings before starting as there are two rings foor 2,4,6 poles. If you turn them exactly opposite they do nothing. In that case the whole ring assembly could be moved on the tube without anything moving. From that position on the adjustments should be done I guess.


There a lot more threads on it. Do a search for Astig, CPC magnets, focus . The Marquee Bill Blue magnetics 101 is also has good info. Its in the Marquee downloads, but it some methods can be applied to all crt's .

Nashou

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barco_75




Joined: 14 Jan 2009
Posts: 169
Location: Chicago


PostLink    Posted: Sat Nov 22, 2014 5:21 pm    Post subject: Reply with quote

Quote:
Look at the 2-pole picture. One side of that is "North" and one side is "South." Imagine an arrow going from S to N. In each set of rings you have 2 rings. If you line them up so the arrows point in opposite directions -- N of one ring next to S of the other -- the magnets cancel out and you have no effect. If you point the arrows in the same direction, they reinforce each other and you have double effect. At positions in between you get between 0 and 2x effect.

The 2-pole has only one total "arrow" resulting from combining the two rings' arrows so it only affects the beam in one direction -- so you use it for centering. You rotate it to determine which direction you're pushing the spot, and adjust the rings between 0 and 2x to determine how far you push it.

A 4-pole ring set has 2 "arrows" in each ring, perpendicular to each other. That lets you affect the beam in two directions, so you use it to change the shape of the spot (turning an oval into a circle by squeezing more in one direction than the other). (I'm a little unclear on the exact mechanism of this one, because the 0-to-2x variation affects both arrows, not just one. I think there are 4 "arrows," 2 pairs 180deg apart, pushing in from 4 directions. You rotate it to line up the arrows with the long end of the oval, and adjust the rings to determine how hard you squeeze the oval.)

A 6-pole has 6 magnetized spots producing 3 "arrows" 120 degrees apart, which lets you control triangularity. You line up the "arrows" with the points of the triangles in your dot, and move the rings between 0 and 2x effect to determine how hard you squeeze the points in.


The description above was very helpful in understanding the cpc magnets. Also thanks for the link, I had been speaking with Galen (zGman) by email and he told me to search threads for his cps magnets tips and bam! you helped me find it. I couldn't find it before, so thanks much.

Couple of questions: First, is it best to start with the 2 and 4 poles 180 degrees apart each in it's neutral position as suggested by Curt? The factory settings are not 180 and Galen seems to state not to start there unless you can't get a good focus. I'm guessing there is a reason to attack the problem each method, but I'm not exactly sure why? Perhaps you can get a better focus at 180, but it screws up your alignment...which then has to be readjusted using the trim pots (which is more work so best not to start at 180 unless necessary)?

For me the 180 degree tip seem to work. I can't find a nice dot pattern other than the barco Genlock pattern. At least I know it is 2 pixels wide by 1 pixel tall. I was able to replicate the third photo showing the focus...I had a donut although it was not in a guitar pick shape more round/oval.

I'm having trouble getting the oval donuts aligned on on its long axis perfectly horizontal (because i'm using the 2 pixel width "dot"). The other item which is not clear is if when doing the 2 pole adjustment if the blurry horizontal lines and blurry vertical lines should be the same width (when using a crosshatch pattern)? I can't get them to be the same width but I can get the sharp horizontal and vertical line in the center of both the blurry horizontal and blurry line.

Lastly, is there something important about putting the cpc magnets as far forward as possible? I had to move them back some because I run out of adjustment for the focus coils.
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barco_75




Joined: 14 Jan 2009
Posts: 169
Location: Chicago


PostLink    Posted: Sun Nov 23, 2014 4:41 pm    Post subject: Reply with quote

Update----I'm getting closer. Picture looks very good in comparison to prior settings. Still curious about the questions above as I'm hoping to understand this process better. I've gone though the astig adjustments for each tube. I'm going to mark my adjustments and see if I can get it even better and if not at least I can easily go back to where I started.

Couple of observations, the green is easiest to observe the changes when moving the magnets. Red is not as easy and Blue is almost impossible unless you have a helper. I even had binoculars but they where not the helpful for the red and blue. If your doing this for the first time, it might be best to start on green so you can see and understand the effects.

1) On Blue Bills tutorial he notes that you should center the image prior to starting. I did have a centered image (not using his technique), however, that goes quickly out of adjustment with the two pole magnets. He notes to rotate focus coils to recenter the image. Is this a marquee only thing? By focus coils does he mean focus yolks? I thought the focus yolks are just to be moved forward and backward and not twisting. Galen (zGman) notes to just to use the trim pots (on horizontal and vertical boards) to adjust. When using the trim pots should the electronic raster shift on the red and blue be set to midpoint (in convergence menu)? There is no green trimpots so I have to move the master raster shift for red/green/and blue away from midpoint (I have an HDfury 1 and it shifts the image). I can shift the raster on red and blue to midpoint in the convergence menu but I'm not sure if I should do this?

2) How important is it to find the cpc magnet neutral position before starting the astig adjustments. I was having trouble finding this (other than just aligning the magnets per Barco service manual photo above). I doesn't seem like it is going to end up in neutral position in the end because you will need to twist the knob and then rotate each pair of 2 and 4 pole around the neck for best effect. In the end, when I ramp up and down the focus the center of the dot doesn't move. I do notice however, that the shadow of the vertical and horizontal lines are not equal width (The shadow for the horizontal line is centered on horizontal, and the shadow of the vertical line is closely centered on vertical, but the vertical and horizontal widths do not match). I was having trouble getting the vertical shadow centered on the vertical line as the magnets did not seem to make any major effect on the vertical line position.

3) Lastly, what is the goal of the electronic focus once the astig is set? Are you to get the lines as narrow and focused as possible visually from standing afar? Or use binoculars and try and make the scan lines stand out (which would assume it has best focus)? I've never been able to see the scan lines before so I'm guessing this is desired as this is a result of sharpness. I was running 1080i prior but now that I see scan lines at 1080i, I bumped it up to 1080p and I think it looks better..maybe slightly blurred but I think better than seeing scan lines. Is this reasonable setting for 808s? Effect that I'm talking about is shown here
http://www.curtpalme.com/CRTPrimer_14.shtm


Last edited by barco_75 on Tue Nov 25, 2014 2:11 pm; edited 1 time in total
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cosaw




Joined: 08 Mar 2006
Posts: 159
Location: Nottingham, England


PostLink    Posted: Mon Nov 24, 2014 3:34 pm    Post subject: Reply with quote

I have a 7" ES machine and from memory it just has the 2 pole magnets (long time since I did astigmatism). As you point out, green is easiest and then red. I too found blue pretty much impossible but I meant to try swapping the lens on blue to see if it made a difference. I just thought there was a fault on blue and that's why I couldn't achieve what I was after.

As regards resolution it's worth trying 720p and seeing if you can see scan lines on that. If you can't then you'll pretty much know that 1080p is too much. If you can run custom resolutions from a PC it would be easiest to see at what resolutions the scan lines disappear.

I tend to run the refresh at a multiple of the source. So for PAL dvd in the UK which is 720*576p*25fps I'll run at 50hz. My eyes don't really have a problem with a little flicker and to tell the truth I can only see it on a pc desktop, as such there is no point in me tripling up to 75hz. On my machine I believe the theoretical resolution will be better at 50hz. That being said, it depends on the "persistence" of your phosphor as to how much flicker you'll perceive. If your phosphor "de-illuminates" (surely not a word but you know what I mean) quickly then you may need a higher refresh rate anyway.

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barco_75




Joined: 14 Jan 2009
Posts: 169
Location: Chicago


PostLink    Posted: Tue Nov 25, 2014 2:09 pm    Post subject: Reply with quote

Thanks for the tips cosaw on the resolution and refresh rate, I was always curious on how people selected the resolution and refresh rate. Finally, I am understanding it. Basically, set the resolution so you can't see the scan lines and then set the refresh so you don't see flicker. Don't go higher on either unless you see better picture quality as it drives the projector harder. I'm a little limited on the adjustments since I don't have a scaler.

I think the machine can do 1080p just fine. I turns out the first blu-ray movie I tested the film quality was a bit fuzzy. I had no clue until, I switched out to a different blue-ray and the image was pretty close to perfect in my eyes. I'll try the lower resolutions to see if there is any improvement.

Does anyone have insights on my questions 1, 2, & 3?
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redfox001




Joined: 16 Mar 2009
Posts: 2251
Location: The Netherlands


PostLink    Posted: Wed Nov 26, 2014 9:02 am    Post subject: Reply with quote

On 1) Yes that is a Marquee thing where you can center the beam with the Focus yoke. On Barco you don't care about centering when doing astig. Just get the picture to not move when you over or under focus. Centering is done later asuming the astig does not move the picture off the phosphor.
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redfox001




Joined: 16 Mar 2009
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PostLink    Posted: Wed Nov 26, 2014 9:07 am    Post subject: Reply with quote

On 2) you ask if the postion of the astig rings does something with the width of the horizontal and vertical lines. I would like to know that too. I think that the 4-pole should fix this.
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Last edited by redfox001 on Wed Nov 26, 2014 1:43 pm; edited 1 time in total
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redfox001




Joined: 16 Mar 2009
Posts: 2251
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PostLink    Posted: Wed Nov 26, 2014 9:08 am    Post subject: Reply with quote

On 3) The electronic focus is set at 58 and then the focus coil is moved to focus the center. That way you have enough electronic focus numbers to get top and bottom focussed without going to 100.
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cosaw




Joined: 08 Mar 2006
Posts: 159
Location: Nottingham, England


PostLink    Posted: Wed Nov 26, 2014 7:27 pm    Post subject: Reply with quote

Well as far as choosing resolutions and refresh rates people used to like to make sure that they chose exact multiples of the source material. However, I think since scalers and Home Theater PCs have got more sophisticated it's probably less important as the softwares and hardwares probably interpolate extra lines and extra frames better than they used to do. I think choosing exact multiples theoretically makes the maths simpler and so may be a safer bet to get a good image. But as said, since the power and sophistication of algorithms has improved it's probably less important. What's still important is the maximum bandwidth of your projector. Say you had a 24fps(frames per second) source and you ran it at 48hz progressive and 72hz progressive. 48hz progressive will stress your projector less because it will use less of your projectors bandwidth. That's where Barco would differentiate between their "Data Grade" and "Graphics Grade" projectors. The Graphics grade projectors have higher horizontal and vertical bandwidth capabilities - they've got more "headroom" to play with.

I think you can get a rough idea of how much bandwidth you're going to be using by multiplying the horizontal resolution by the vertical resolution by the refresh rate. Someone correct me if I'm wrong but when dealing with interlaced images you have to make sure you divide by two or halve the vertical resolution to get the maths to work.

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barco_75




Joined: 14 Jan 2009
Posts: 169
Location: Chicago


PostLink    Posted: Wed Nov 26, 2014 10:10 pm    Post subject: Reply with quote

On item 1, any comment on shifting the Red and Blue to 49 in the convergence menu and leaving green at 32? Is this method placing more or less stress on the digital controls since the adjustment is only available in the convergence menu?

On item 2, I would like to know too...picture looks good but the lines are not equal

On item 3, when setting on 58 (splitting hairs, Barco says 57) once the focus yolk is set is the final position of the electronic center focus going to likely best at 58 (57)? I couldn't tell much difference between 49 and 57. I assume you want to select a resolution where you can see the scan lines and adjust all the focus so you can see the scan line. After complete, select resolution to make scan lines disappear.
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