I finally have my astig adjusted after finding the magnets were never in the right location on the neck. Even though I had seen the diagram on proper placement, I hadn't interpreted it right because the diagram is pretty poor for the one thing that's important. That little gap you see next to the text "15 mm" means that there's supposed to be a 15mm space between the ASTIG coil clamp and the leading edge of the CPC magnet assy. None of mine were in the right place since the previous owner had moved them. No wonder I couldn't get each pole to do what it was should.

http://home.new.rr.com/arseneau/HT%20images/neck.jpgNOT SHOWN TO SCALE

No wonder I couldn't get each pole to do what it was should.

That's funny - Lech Walesa had the same problem.

OK, I'm leaving now...

Well at least he had Solidarity going for him :).

I found that the distance of my XG135 cpc magnet to focus coil is more than 15mm. Should cpc magnet be moved forward so that the gap is 15mm?

I found that the distance of my XG135 cpc magnet to focus coil is more than 15mm. Should cpc magnet be moved forward so that the gap is 15mm?It's ok as long it's more than 20 mm from tube end and astig is good. I move magnetic unit along tube neck to find best position for it. Focus yoke isn't best reference for magnetic unit, since it need also little moving to find sharpest position.

Those dimensions in manual are still good starting points for tweaking. :)

When you move the coil for best focus, do you move both the sweep and astig coils? There doesn't seem to be much room for movement before you 'undock' the astic coil from the bevel on the end of the sweep coil so it would seem you need to move them in unison?

I move just focus yoke. Deflection yokes should be against bell, moving those would chance raster size.

I'm talking generally, since I haven't ever seen NEC XG.:D
Maybe XG hardware wont allow to move just focus yoke and hardware guides yoke to best position.

Those dimensions in manual are still good starting points for tweaking

Is that I need to move the cpc magnet backward and forward starting from the 15mm gap of the focus coil? How to determine the cpc magnet is at the best position on tube neck?

Thanks

don't want to sound like a old fart and everyone probably knows this, but do remember when moving these coils not to over tighten, if you do so it will always = :( followed by = :mad:

it is best to move them around and see where things come together well, they will end up in difference locations for each tube, don't be affraid to tinker with them for hours on end, it will give good results ;)

-Gary

don't want to sound like a old fart and everyone probably knows this, but do remember when moving these coils not to over tighten, if you do so it will always = :( followed by = :mad:

it is best to move them around and see where things come together well, they will end up in difference locations for each tube, don't be affraid to tinker with them for hours on end, it will give good results ;)

-Gary

I agree 100%, but there should be a disclaimer, it can take hours to get them right, I spent about 3 hours on each. The projector was ceiling mounted my eyes are not good enough to see the dots so I rigged up a moveable screen on a tri-pod so I could see them better.

http://www.acdnow.com/Theater/magfocus.jpg

Mike

Hi, Mike

I already done those cpc magnet adjustment for hours many nights. Thanks for the tip on moving the dots close.:)

Gary,

it is best to move them around and see where things come together well,

How would those dots look like when moving the cpc magnet position along the tube neck?

I have done cpc magnet adjustment in accordance with Guy's instruction. In pole 2 adjustment,the bright core is centered inside flare but bright core is not distinct even the contrast is 100%.

In pole 4 adjustment, the blobs are round in underfocus. When I ramp the focus to -90%, the flare is not round but turn to oval sharp. If I adjust the flare become round, the blob in underfocus is in oval sharp.

I'm confused whether the blob and flare should look round when the focus is ramping from overfocus to underfocus?:confused:

I'm confused whether the blob and flare should look round when the focus is ramping from overfocus to underfocus?



they should keep their shape throughout the focus range and also when having the grid up they should stay converged without moving away from each other. If The dots or grid move away from each other while having all colors on and ramping the focus its most likely because you have not "nulled" all the CPC magnets.

Athanasios

If The dots or grid move away from each other while having all colors on and ramping the focus

I didn't check that with all colors on. With only one color (either R,G,B)is turned on, the grid lines are turning to thick halo lines when the focus is ramping. The bright thin lines inside the halo thick lines remained in center.

its most likely because you have not "nulled" all the CPC magnets.

Before I adjust cpc magnet, electronic astigmation and focus return to 0. I had overlapped all the tabs of 2,4,6 poles. Is it nulled the cpc magnet?

Thanks for the input guys! Lots of good ideas.

Like RickL, I have a few questions, so I'll put them forth as my guess as to the order/conditions and what to look for: So this is my interpretation of what you guys are saying. NOT FACT but my interpretation
Start with settings nulled. Menu astig values at 0, CPC magnets with tabs aligned (null position), CPC magnets on yoke starting at factory recommended spot. Raster centered on CRT face.
Set the FOCUS yoke placement by moving slightly forward/back, watching crosshatch pattern to balance horiz/vert line width. To set the FOCUS yoke angle, the NEC manual recommends setting TOP side astig H to max (making the dots elongated lines going mainly up and down), rotate the FOCUS yoke for most vertical result, return TOP ASTIG H value to normal. Hand tighten yoke lockdown strap just until screw turning resistence increases. Overtightening will cause the CRT neck to break.:eek:
Adjust CPC magnet placement by moving forward/back with CPC tabs opposite (not null), looking for place with strongest intended effect (2-pole opposite?, 4?, all?)
Next, adjust CPC magnets by observing overfocused dot pattern (adjust contrast to MAX to see bright core). Adjust 2-pole tabs to center core, adjust 4-pole magnet for best roundness of flare (blob around the core), adjust 6-pole magnet (the set nearest the bell) to remove triangular shape. Concentrate on the appearence at the center of the screen.
Re-center raster placement and repeat CPC adjustment.
Adjust Focus pots for best focus, make more coffee
Make electronic astig adjustments to fine tune Center, Edges, Corners by observing + pattern or crosshatch. Adjust V for to 'focus' + to smallest overall line width, adjust H to balance Horizontal width with vertical width.
Drink coffee made earlier
Adjust final focus via menus for Center, Edges, Corners
Sleep, it's 4am.

Corrections welcome.

The magnets are nulled when you turn the knob and slightly move the ring back and forth and nothing happens, this is when the magnets have no effect to the beam hence they are nulled. Then you center the raster ,it is different for all projectors. then you proceed to do the astig and get the round dots and you will most likley have to go back and re center the raster again for each tube. Then go back and recheck the astig dots, then back to make sure the raters are centerd. this goes back and forth till you have nice round dots and a centerd grid where ramping the focus will not move the grids out of convergance. Also if your projector has Zone focus in a service menu do that in between Astig and raster centering.

its tedious work my calibrator took about 8 hours just on this. I plan to attack my second projector with this method..i need a whole day off for that!!!

Athanasios

The magnets are nulled when you turn the knob and slightly move the ring back and forth and nothing happens, this is when the magnets have no effect to the beam hence they are nulled.
I like the knob arrangement and I've seen them on SONY's. The NEC's that I own have tabs but the principle is the same. With Tabs, the tab offset from each other adjusts strength and the rotational placement around the neck determines the direction.

Then you center the raster ,it is different for all projectors. then you proceed to do the astig and get the round dots and you will most likley have to go back and re center the raster again for each tube.

I forget to mention centering and it is a good consideration since it is apt to change from the CPC adjustment.

Thanks Jerry for the write up of the procedures.:eek: It looks like I miss few steps in the cpc magnet adjustment and forget to stock enough coffee :D

A memeber of Curt's forum posted a thread about the NEC PG cpc magnet adjustment with pictures. Its worth to take it as a reference. He didn't finish the write up.

http://www.curtpalme.com/forum/viewtopic.php?t=10078

Thanks Athanasios reminding the check of raster centering. Welcome anybody to chime in and give us advice on the procedures.

Ricky

Jerry,

To set the ASTIG yoke angle

In step 2 of your write up, is the "ASTIG yoke" referred the Focus coil/yoke? The manuel on tube replacement mentioned to rotate the Focus coil/yoke a bit. Can't remember exactly. Forgive my poor english.

Ricky

Jerry,



In step 2 of your write up, is the "ASTIG yoke" referred the Focus coil/yoke? The manuel on tube replacement mentioned to rotate the Focus coil/yoke a bit. Can't remember exactly. Forgive my poor english.

Ricky

Yes, I really should have called it Focus yoke like most people :D. The same yoke adjusts both Focus and Astig and is the one not against the bell. The one against the CRT bell is the sweep yoke.

The one against the CRT bell is the sweep yoke.

I noticed on my XG that these pieces have silicone on them just like the 2, 4 and 6 pole magnets do. Should I leave well enough alone if the silicone is intact?

I would not break the factory seal on those tabs on the sweep/deflection yoke. My guess is that those are used to align the yoke squarely on the neck which should not vary between from tube-to-tube. The NEC XG and PG pj's use electronic raster centering and those tabs are not for that purpose.

Gotcha! Thanks! Just killing time reading until I get mine back together.

I would not break the factory seal on those tabs on the sweep/deflection yoke. My guess is that those are used to align the yoke squarely on the neck which should not vary between from tube-to-tube. The NEC XG and PG pj's use electronic raster centering and those tabs are not for that purpose.

That's not right.

You need to rotate the deflection coil to get the horizontal crosshair level, so you don't use much TILT.

That's not right.

You need to rotate the deflection coil to get the horizontal crosshair level, so you don't use much TILT.

Mark, maybe I'm thinking of something else. I'm not sure what to call them but they did have silicone on them. I turned the deflection yoke independent of these things. Here is a picture I found from when I did a tube change recently. The black tabs with the white silicone on them, little plastic square tabs sticking out at the sides.

http://img.photobucket.com/albums/v641/dropzone7/DSC02749-1.jpg

Oh, ok. No, you turn the whole black deflection/convergence coil as a unit, holding onto the black box bit on top (stay away from the exposed coils!!).

Oh, ok. No, you turn the whole black deflection/convergence coil as a unit, holding onto the black box bit on top (stay away from the exposed coils!!).

Ah, I did it right then. I figured if these tabs had silicone on them then they were okay. I always just rotated by grabbing the box portion as you say.