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Yikes, Holy Focus Guy Kuo - Page 2

post #31 of 163
Thread Starter 
Just goes to show ya. Take a CRT owner who thinks he's got it right, tell him you know a way to make it better and I'll bet he will listen. I'm glad I did. Thank's Guy.

Chip S.
post #32 of 163
bump
post #33 of 163
Thread Starter 
Not an unusual amount of replies, but look at the number of hits.
I think I've created a monster...

Chip S.
post #34 of 163
I'll put up some quotes from his message and then ask my questions. At one point Guy says.....

"Do a rough beam and optical focus. Mark the exact screen center with a lightly applied triangle of 3M's blue easy release masking tape. *** do NOT substitute another brand tape here **** "

On my Sony 1272, I assume the optical focus is with the lenses (R1/R2, Etc) So what is beam focus and how is it done?

"Beam astigmation fine tunes the electron beam lens to create a uniform electron spot with with minimal flaring. Poor astigmation can make electron beam focus impossible."

I think I understand that astigmatism is adjusted with the 2 and 4 pole magnets. If this is the case then how is the electon beam focused?

"The CPC have 2, 4, or 6 magnetic poles, but don't confuse that with the number tabs on the rings. One cannot actually see the poles. By varying the angle between the two rings of a pair (moving tabs in opposite directions) one varies the intensity of the effect. Rotating a pair about the axis of the tube neck (moving tabs in same direction) changes the directionality of the effect. "

OK, I got this one, the 2 and 4 pole adjust the shape and intensity of the dot.

"The 4 Pole alters the ovalness of the electron beam lens. Adjust this while displaying a dot pattern while contrast is moderately high. Intentionally UNDER focus the electron beam making the dots into uniform blobs"

So to focus or under focus the electron beam I use the lenses? I'm really confused.

"Display a bright window pattern and intentionally defocus the electron beam to make the scan lines disappear. Adjust center optical focus while viewing the screen through binoculars. "

I think all of my questions have to do with the difference between optical focus (using the lenses I assume), adjusting the shape of the electron beam (known as astigmatism and adjusted with the 2 and 4 pole magnets), and then focusing this perfectly shaped dot. So how do I focus the dot? Is adjusting the 2 and 4 pole, also know as astigmatism the same as electron beam focus?

I think it is all of this new terminology thast is causing me such difficulty.

Thanks Guy for the great instructions, I'm just having trouble with the terms. I hope somone has a few minutes to explain this to someone new.
post #35 of 163
Hi Areno,

I'll try to answer some of your questions,

Quote:


On my Sony 1272, I assume the optical focus is with the lenses (R1/R2, Etc) So what is beam focus and how is it done?

it's electric focus, the 3 pots under the 3 screen or G2 pots, on right side of your sony, at the right of remote



Quote:


So to focus or under focus the electron beam I use the lenses? I'm really confused.

you have to focus and underfocus with electric focus, I quote an explanation of astig adjustment posted by Chuck Williams (not sure):

Quote:


What you want to see here is while moving the electronic focus from
100-0 and back to 100 the dots have NO movement on the screen. If they
do, you need to adjust the back ring to get the minimum movement.

As mentioned above, display a dots pattern. Set dynamic astigmation
controls to center position. This allows you to set the magnets to do
most of the work and just fine tune later with the dynamic controls.
Binoculars are very handy but must be of large light gathering power.
You'll need to significantly increase contrast setting to above normal
to see things clearly during astigmation adjustment. Also work with one
gun at a time. Cut-off the other two. Once astigmation is complete,
don't forget to return contrast to normal before final beam
focusing.Turn
e-beam focus to max one direction then the other. In one direction
(underfocused)the dots will become large circular or oval blobs with
uniform
brightness within the blob. In the overfocused direction, the spots
will
have a central luminous portion and a dimmer halo. These both need to
be
examined when doing astigmation.

The 2 pole magnets are the rearmost of the shaper magnets. These are
used to center the electron beam in the middle of lens. Place the
system
into overfocus to show the central luminous point and surround halo.

The 2 pole magnets deflect the luminous point. Twist the knob to alter the
amount of deflection. Rotate the knob about the tube neck to alter the
angle of deflection.

If you use a center cross pattern instead of a dot pattern when
centering the e-beam it's easier to see when the beam is centered in
the lens.
A center cross shows up as fat lines with a central luminous line. Just
adjust the 2 pole magnets to make the luminous portion of the vertical
and horizontal lines centered within the fat linear halos. It's easier
to see than staring at a point with a halo.

The 4 pole magnets are frontmost of shapers. It is used to alter beam
shape to a circular shape. One sets the tube to underfocus and displays
a dot patter.

This turns the dots into a larger,uniform blob whose shape
is adjusted using the 4 pole magnets. Twisting the knob adjusts degree
of oblongation. Rotating the knob about the CRT neck alters the axis of
the effect. Make things as dead round as possible for the center
dot. Turn focus up and down and make sure things track correctly. You may need to
make some minor tweaks to the magnets to get things just right.


The astigmatism adjustent can seem difficult at first go but once you do one tube you will
easily do the other two. With a signal applied first call up the cross hatch pattern then
kill the red and green guns. Turn the blue pot SLIGHTLY counterclockwise to unfocus the gun
then adjust for beam centering with the neck rings. Then call up the dot pattern and turn
the blue pot clockwise past the sharp focus then agjust the other neck rings to get the
beam shape as round as you can. Then bring the pot back to focus and reset color bias to
get a white square.


Focus the dots as well as possible. Then go on to the next gun. When
all three guns are completed, you now have "static" astigmation
optimized and this means the dynamic astigmation system is under less stress.
Perform dynamic astigmation for each zone as well as beam focus.

Now that beam focus is optimized, it's time to recheck optical focus
for center, corner, and Schempflug (horizontal and vertical flapping)

You can check lens flapping by using the center lens focus (rear
wingnut). Display an inverse +pattern and adjust center focus to make
the
center of the top screen edge perfectly focused.Note the lens control
position. Next adjust the lens to make the center of the bottom screen
edge perfectly focused. Is it the same position. If yes, vertical lens
flapping is dead on. If the two positions are not identical, you need to
readjust vertical Scheimpflug (flapping). Similarly compare the perfect
focus positions for left vs right edge. Finish by adjusting center focus to
perfection and touching up the corners using corner focus (front
wingnut).


good luck Areno!!!

Regards

:-p

Bruno Lovisi
post #36 of 163
Perfect Bruno!, Thanks, I can't wait to get home to give this a try.
post #37 of 163
Bruno got it. Electron beam controls are done using the electron beam adjustment controls (beam focus, 2 & 4 pole magnets) and definitely not the optical focus controls on the lens.

I'll just add a caution to leave the screen potentiometers alone. They are so close to the beam focus controls that it's very easy to accidentally turn one of them. The unfortunate result is a badly maligned gray scale. Taping a piece of cardboard to cover the screen controls before you start may save you an unanticipated problem.
post #38 of 163
Thanks Guy! Things are really looking good now that I have worked through your focus steps. Thanks Again. Adam
post #39 of 163
Hi,

A few questions for Guy.

I've been reading your focusing tips, but I have a few questions. I'm running a BG808. First, how would you do your intial mechanical alignment of the crt's on a Barco? You said to use a white field. How does that work? I do have Avia. Or do you use the setup crosshairs on a Barco? Second when adjust the astig, do I follow the same procedure that you outlined for the Sony in the above posts? Do I have to rotate the pins on the magnets as described above, to set the astig or do I just have to rotate the magnets on the necks as someone said in another thread?

Thanks for your help!

DougK
post #40 of 163
If you want to follow the technique, then you'd use a field pattern from AVIA rather than the internal cross hair. The advantage of the field is that it is easier to see that the edges of the field are equally spaced relative to the CRT glass edges than seeing if the cross hair is in the center of the phosphor.

The astig magnets on your machine are handled using a combination of twisting the little knob to vary the amount of effect of the CPC magnets. You also twist the entire assembly around the axis of the tube neck to change the direction of the CPC magnet effects.
post #41 of 163
Time to do a bump. The only thing I'd add is that those with the S&V Home Theater Tune-up disc should go into the video calibration section's special test section. Try out the new Focus and Crosshatch patterns. Both are in single pixel resolution, the finest that can be encoded on DVD. That's double the resolution of what I created for AVIA.

The focus pattern is as fine as possible, but you should also check with your built-in focus pattern to see which works better for you.

The new crosshatch is specially colored so you can now perform convergence of all three colors without needing to turn off or cover any of them. It's now practical to directly converge blue on green instead of the old, indirect red on green then blue on red sequence.
post #42 of 163
Quote:


Originally posted by Guy Kuo
The new crosshatch is specially colored so you can now perform convergence of all three colors without needing to turn off or cover any of them. It's now practical to directly converge blue on green instead of the old, indirect red on green then blue on red sequence.

Being somewhat colour-blind with regards to red and green I used to find calibrating Red against Green very difficult because green output is so bright compared to the red gun leaving me unable to see fine misconvergences due to my colour blindness. Inspired by the idea above of "specially colouring" the convergence cross-hatch, I tried a new approach to converging red on green, which simply involves lowering the green gain before converging, so that red is the brighter of the two colours; I am then clearly able to see the red lines scanning through the green lines and get perfect convergence. Same works for blue/green. Once done I restore the green gain to it's original setting.

Mark
post #43 of 163
Thread Starter 
Wow, look at the mileage this one's getting. I'm glad it's been so usefull to others. It worked great for me.

Chip S.
post #44 of 163
Thread Starter 
I guess this as a good of time as any to bump this back up to the front. As soon as I get my new setup remote from Curt and my Escalara back I'll be trying this focus setup again. I'll be taking down the ECP 3101 and replaceing it with a NEC 9PG plus. Can't wait no mo bye...

Chip S.
post #45 of 163
Guy,
first off, thank you for this guide, your information is as always priceless.
Now you mention that home theater tune-up DVD - where can we get it ?
Thanks
Oliver Klohs
post #46 of 163
Bump. Main posting updated and expanded. New crop of CRT owners on forum.
post #47 of 163
Oliver,
the best tune-up DVD manufactured is called AVIA. Not sure where you'll be able to get it, but it's a must have for the hobby.

I recommend it to everyone, it's very easy to use. You're not serious about HT until you own it.

Do a search on the internet for: Ovation Software or AVIA.

I only hope that on the next version you'll be allowed to bypass the intro.
post #48 of 163
Mike,

thanks for the tip, but I do already own Avia and VE and was hoping for something else Guy mentioned in this thread called S&V Home Theater Tune-up disc.

Oliver Klohs
post #49 of 163
Oliver, you can find it at Amazon if your local Fye or other video seller doesn't have HTT in stock.

Mike, just hit the menu button on your remote. The current AVIA disc already allows you to go immediately to the menues without forcing you to wait for the intro and copyright screens to display.
post #50 of 163
Thanks Guy,
I will order the HT tune-up today.
Oliver
post #51 of 163
Guy,

Would your great set of instructions change for me since the screen I plan to use is curved (horizontally only, not torus) like Alan Gouger's $200.00 curved screen thread? Please give me your opinion on this. Thanks!

-PGPfan
post #52 of 163
I don't think it would be materially different. You will be automatically compensating for the screen curvature as you go through the various focus steps.
post #53 of 163
"Home Theater Tune-up disc..."

Guy,
can you tell us more about this product?
post #54 of 163
Guy,
This is the first time I looked at this thread and it is very good, you explained it very well. One of the areas that gets overlooked is when you move the raster centering it also changes the astig.

The set up from the factory is based on the 100" diag 4:3 format ceiling front.

Because the average HT set up is a bit different this procedure does make an improvement to dial it in to your application, screen, freq and phase.

A helpfull hint on the XGs it to hit the SW S5502 switch on the HV PWB to assume high beam mode, this helps to see the core, (dont forget to shut it off, protruding) also in the astig defocus mode if you hit test/end button it will go to the actual display but remain in astig mode, I like to use a external H pattern black back raster and dial the flair in by looking at the H using the cursors to get the H perfect, you can see this flair "pull" in all directions if its not optimum.

I think the disc is "Sound & Vision Home Theater Tune-Up" Ovation Software. I got mine from Amazon, also has DD / DTS audio set up 5.1-6.1

Good piece of work here Guy. Doug
post #55 of 163
Thread Starter 
Just time to bump this again. We have the need for wisdom...

Chip S.
post #56 of 163
Doug wrote:
> One of the areas that gets overlooked is when you move the raster centering it also changes the astig. <<br />
Does anyone have a complete chart or list of the chain of dependencies? I.e., which adjustments affect other settings? Some of these are unexpected, even to non-newbies.

- Tim
post #57 of 163
This post is priceless...stop the bumping and stick it at the top forever or better yet, let's start a Meta-Faq as is seen in the Home Theater PC part of this forum! People are always asking where to look so why not give them a list of posts for the beginner up to the expert!

I have already tried to start a post on the Horizontal Line Problem so all manifestations and solutions are combined in one post:

http://www.avsforum.com/avs-vb/showt...ferrerid=22283

Let our forces combine and call Captain Pla.....no wait sorry...let's combine the knowledge already present on this forum and make it more easy for the newbie (which I still am myself) to find the way in the big CRT-forest.
post #58 of 163
Holy Moly!

What a great post, Guy!

Thanks!
post #59 of 163
What would happen if you totally remove the astig ring?

Would that damage the tube?

I have lots of problems focusing my blue tube - it's totally out of whack - I am not talking a little out of focus here - I'm talking totally unreadable.

So, I played with the astig ring like it's mentionned here, and I decided (probably wrongly) to remove the ring and see what kind of result I would get. The result I got is that the output of the tube is now very very faint (maybe 5% of what it was before) (even after I put the ring back)

Could the removal of the ring cause this problem?

Thanks!

Sylvain Dumas
post #60 of 163
Guy,

Just some additional tips.

Rather than using blue scotch masking tape, I use post-it notes. I cut a portion of the note that has the stick on it and a portion without the stick to allow easy removal. I choose a color of post-it as needed/desired

I also, after marking the middle of each edge, place thin, black fishing line as horizontal and vertical center lines. The fishing line than cotton string is better as it does not stretch. The horizontal line must be tight as there will be some droop in the middle. I also make a diagonal from each corner. These should be tight as well. All should meet at the center if the screen is properly square. I then use a level to see if the horizontal and vertical lines are true (assuming the screen is true).

Finally, another way for finding center is to take a string and fold it in half. Tie a knot at the center point with a small loop in it. Now from the center point, make each side of the string identical in length. The length will depend upon the use. Attach each end to the left and right sides at the middle point. Hold the center point and pull it tight. The center point of the string (when adjusted to the needed length will lie on 2 center points (raising the V high and low of center) of the vertical string. If you make it long, it should be dead center on your projector's center tube's line. Do a point in the front and back of the projector's centerline to guarantee that it is pointed square with the screen.

In a similar fashion, connect to the V string to the top and bottom center's of the screen and check the horizontal string at two points.

Hope this helps,

Ira
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