CurtPalme.com Home Theater Forum

[karmat63]

[shar1950]

I would also be interested in knowing how to do the cpc magnets and getting good beam focus !!

[Nashou66]

EDIT: I should put this in its own thread....


Hi Guys, I just did mine last night and got great results in half an hour for all colors.

A little explanation of how the rings are used and what movements do what inside the ring.

The 3 knobs or sets of tab's depending on your CPC set, are actually two thin rings, with either two poles(centering)
3 poles(triangularity) and 4 poles( to get roundness) .

The rings can rotate around the tube by moving the knob which moves the poles on either half of the ring set together.

The halves of the rings can move separate from each other by twisting the knob or separating the tabs in opposite direction
on the ring set.

So by moving the ring around the tube both poles move together,
Twisting the knobs or moving the tabs away from each other move the poles on each half in different directions.

To null the CPC magnets its easier to take them out but it can be done on the tube neck. Move the tabs on the opposite side of the knobs all together, this sets all the poles on either half together.

So now we have the mechanics of how the Color Purity Control magnets work
with each other.


First you need to disconnect the Astig coils. I also zero out convergence in the green service menu, more on this later.
Also go into the RGB service menu for focus and get each color and zone as best as you can with out the CPC's being set.
We will go back later after we get the dots centered and round as best we can.

After the focus is set, ramp up contrast to 100 and use your favorite dot or dot/grid combo pattern.

Most say to use the lowest internal frequency and then move up to the one you using, in the sake of saving time i went with my resolution i usually use. I started with getting the dots round with the two back rings, the 3 pole and 4 pole ring sets( This is for 6 pole CPC sets) making sure they are nulled, then i adjust, and once i get them round, looking at only the dots in the screen's center I then use the front ring to center the bright dot going back and forth between in unison movement and twisting.

Now this is why I zeroed convergence, i want to get the grid to center using the focus coil as close as possible, its not 100% necessary the get it dead on but the closer the better and with out sacrificing dot location in the center of the blob.Lock one Wing nut on the focus coil to hold that position. I go back and check the roundness of the blob and adjust that if needed. Then I go back and check the Bright centered dot. Mine moved just a bit on all colors i tried so I adjusted it once more using both rotation of both halves of the rings in unison and twisting the knob which moves the rings halves in opposite directions.
just a little i usually needed.

Then i checked the ramping of the focus to see how bad the dots/grid moves to a reference point( I used a piece of Blue painters tape) I did not get perfect non movement but it was close with out having to sacrifice having the bright dot in the center.

I then locked the focus coil's other wing nuts adjusting the grid as much as I could with the one wing nut locked already.

Now re connect the Astig coils and do all zones in the set up, my original factory setting were all of as they would be since each location of the PJ would need different CPC set up and electronic Astig.

Now put contrast back to the levels you use and set RGB focus one more time for all zones in the RGB focus service menu.

Then i went through the mechanical set up guide to get the green back to center and then also moved the red and blue tubes to get those grids lined up.

then lock those lens bolts up and do a convergence.


THATS IT !! Wheeeeeooouuu!

Athanasios

[cmjohnson]

To add to this, and put it in really simple terms, CPC adjustments NEED to be done with no interference from any active correction circuitry (astig or zone focus or even convergence) if you want the best results. In fact, the centering, astig, and triangularity adjustments
can NOT be done properly when focus is sharpest! You intentionally defocus the image (dot pattern) so that the dots are, when everything
is ideally adjusted, nice ROUND blobs with well centered bright central spots. They are round, not egg shaped, not hexagonal, not
triangular, and the center is brighter and well centered.

This is just PART of the total magnetic setup, but it's important to do it right. Ideally you don't want to run anything on the tube neck
at the time other than the deflection yoke, for the first stage. If your focus magnets are at the ideal strength, you WILL have to plug
the focus coils back in and then neutralize all zone adjustments and ramp the central focus adjustment to a well defocused setting so
the dots become blobs, as when the magnets are at ideal strength, they'll give pretty good focus on the tube face even with the coils
completely disconnected. Which is NOT what you want when setting the CPC magnets.

There is a lot of interactivity between the flare centering (2 pole rings on the CPC pack) and the centering that's done by shifting the
focus yoke. You'll have to play with it and establish the ranges of adjustment for both the flare rings and the focus yoke, and then
adjust for the best centering of each of them. If you can then ramp focus from 0 to 100 and the displayed image doesn't move,
you've got the centering set just right. It can be rather tedious, but the difference between doing it right and settling for less can be
the difference between a machine that actually resolves 1080p, and one that is too soft to do that properly.


CJ

[Nashou66]

Chris , I assumed most know that you need to defocus and over focus to see the bright dots and get the round blobs to do this set up.

I disagree with your point of setting the normal focus to 50 for all zones in the RGB focus menu. i tried it this way and it changes the centering of the bright dot. here is why, not all focus magnets are the same on each tube, some have more or less gauss , also you need to defocus and over focus and with out the electronics connected its impossible. So first you have to focus , with the astigs disconnected, all the colors in all zones. This way your starting the CPC at the same point. And really the outer zones dont have to be adjusted since your looking only in the center. I tried it both ways, setting all focus to 50 and the way I described above, and the new way i did it worked the best .

Athanasios

[stefuel]

My take on the whole subject. Any projector that utilizes CPC magnets for correction of dot shape and dot centering (with no electronic astigmation controls) is global and should not make any difference what resolution you are sending it. The use of a "lower resolution" to set them, allows for a bigger spot to see while setting them. It is a mechanical adjustment and if done correctly and you have round blobs and centered cores at 480P, you should have the same but smaller dots at 1080P. If a display device employs some sort of electronic astig correction, it should be nulled prior to CPC adjustment.

My opinion is nothing should be unplugged or disconnected durring CPC adjustment as that would or could effect the magnetic field surrounding the tubes and could effect the final result. I'll go as far as to say that when your done and the covers are on and the projector is closed back up that you should re-check to see if everything is still OK. To get these adjustments correct on a NEC is trial and error as everything changes as soon as you close it up especially raster centering.

[mp20748]

[Nashou66]

I agree chip, But i got nice sized dot with my res, its just easier to pull the Astig,s and IIRC Scott told me the same once. Anyhow i got the best results I ever had and the thinest grid lines as well. Thanks for the added input!



Athanasios

[dturco]

[cmjohnson]

[shar1950]

thanks for the explanation guys, if one reads this a few times, one get what is happening. Now another question, is there a simple test or procedure to see if I really need to redo the cpc magnets on all the tubes ?

Also I'm just feeding my pj 1080i from satellite, which internal frequency should I use ?

[Nashou66]

From the consensus here use the lowest internal frequency.

Put up the dot pattern and raise contrast. press color 1 for red, 2 for green, 3 fore blue . Looking at each color separately lower focus to 0 and see where the bright dot is, it might not even be there where you'll see one side of the blob/fuzz brighter. if it is not in the center and the fuzz or blob is not roundish you need to do the CPC's.
when you raise focus to 100 the fuzz turns to a blob that should be brighter on the outer ring evenly and lighter in the center and they should be round.

Athanasios

[stefuel]

A very easy and quick check is to take a piece of blue easy release tape with a piece of white masking tape on top of it.Put up a dod pattern. find a dot in the middle of the screen. stick the blue tape so the dot hits it in the center. Take a pen or pencil and draw a X where the dot intersects. Then over/under focus the dot for the color in question and see of it's center stays over the X. If it stays over the X and the dot is round leave it alone. If the dot is not round or it moves while adjusting the electronic focus it needs adjustment.

It's not rocket science. It just takes practice and a couple of pots of coffee and nerves of steel and a couple of loose screws and a couple of more pots of coffee and a explanation to the wife why the trash hasn't been taken out and why you can't remember your kids names and to change your underware after you forgot to go to the bathroom when you really needed to and ........................................................................................

[Nashou66]

[stefuel]

LOL!!! So how are those thomas tubes Dots Chip?


Almost had a heart attack. I cam home and the significant other informed me that the PJ just shut down so she shut off everything else. So I pushed the master power on button. The PJ fired up and everything else in the theater did also.
When the PJ finished booting up the green went full on then the PJ went into protection and shut down. That was with the green neck board that had the streaking problem. I put the snapping one back in after relocating some of the jumpers for additional space. The PJ fired right up normal and so far no snaps.

Dots adjust out just fine

[garyfritz]

[cmjohnson]

After I finish building my remagnetizing jig and set up my coil winder, I'll be able to turn those coils into Advanced FrankenYokes, perfectly suited for a Marquee.

Of course I'll give updates on this when I've made real progress and actually have a service to offer here.


CJ

[shar1950]

Well, still a little fuzzy about how to null the magnets. Read some where, if pj is ceiling mounted allready, just rotate the knobs away from the ceiling. After it is at the bottom postion slowly rotate the knob and then turn tab back and forth around the tube, looking for the least amount of dot movement. After twist knob and turning tab, find where there is no movement of the dot.

[garyfritz]

Yes, with the Marquee magnets there are no tabs to mark the "null" position. Just rotate the magnet while turning the knob. You'll get to a point where rotating the magnet has no effect -- that's the null point know position. Your magnets might have marks on them that line up in the null position. If not, you might want to add some yourself for future reference.

[Nashou66]

Thats the hard way to null, on the opposite side of the knobs or close to the opposite side (depending on how much the the knobs were twisted therefore moving the tabs on the other side further away from each other) there are tabs for each half of the ring, just put them together and the swing the knobs back to where you can touch them. Or just remove the card cage and pull the CPC mags out, null them and put them back on. Moving and playing around with them can be a bigger pain than just removing them and knowing for sure they are nulled.

Athanasios