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Discussion Starter · #1 ·
My rasters light up unevenly on my NEC XG-852: The right side of the rasters have an obvious "light patch" of some sort, that faintly shows up in the projected image during very dark scenes.


Here are pics of the raster (no lenses) at 1280 by 720 Resolution:
http://www.davidjfriedman.com/XG852/...ng/Raster2.jpg


Its slightly more evident if the signal is off:
http://www.davidjfriedman.com/XG852/...ng/Raster1.jpg


Here are shots at 1360 by 768 resolution (through lens)
http://www.davidjfriedman.com/XG852/...60-768-Red.JPG


And here is how that looks on my screen---notice the double line on the right side of the screen
By the way, I don't live in outer space, the starfield effect is digital camera artifacts from an 8 second exposure.
http://www.davidjfriedman.com/XG852/...768-Screen.JPG

Any ideas? What should I do?


Thanks!


David

 

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Does it do this with no signal applied at all.. i mean totally disconnect any input signal.


Does it do it using the s-video input?


Have you tried setting up a new memory input and seeing if it still does it?
 

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my guess is that the tubes are not centered correctly. i could be mistaken but i had a similar problem except it was not as bad. doug baisey came over to realign everything from scratch.
 

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Discussion Starter · #4 ·
Thanks for the reply Cookie.


I just checked, it does this even when NOTHING is connected to the PJ.


Also, it was doing this before (and still doing it after) I did an EEPROM reinitialization (which totally wipes out all the electronic adjustments, and of course all the resolutions settings.)


In any event, the ONLY connection I ever use is the RGBHV coming from my HPTC.


David
 

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Discussion Starter · #5 ·
Jon,


Are you referring to some type of mechanical centering? or some pot somewhere?


The same pattern shape appears on all 3 tubes (athough it's more promiment on the green, and on some resolutions and settings its not even noticeabe on the other tubes)


Could there be a setting somewhere that is common to all three tubes that relates to this?
 

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If the image is identical in all three tubes, it's not centering.


David, the rasters should be just barely visible as you look into the lenses. You indicate you can see the unenven illumination in dark scenes. Does your hand cast a shadow on the screen when you're showing a 0 ire full black field? If it does, your G2 controls may have been mis-adjusted by a previous owner trying to get more light output.


Also, you indicate it is not visible at other resolutions. Are they lower, perhaps?
 

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David,

This can be one of a few thinks that is causing this. Lets approach the easiest for you to set up first.

This could be caused by your Reference White Settings settings under the adjust menu not properly set up. Specifically the Black Bias, although the others could have an effect. You did mention that you did a reset of the machine which would set all these back to 50%.

Before you go in and fool with any of these settings, check to see where they are right now. If they are all at 40% then they need to be set. If they are at something else copy all the numbers down so that you have a place to return to in the event you are not successful at resetting these.

Do a search here and Guy Kuo whote a very good procedure on doing all these settings using AVIA. It is a very good method and better than the NEC service manuals method.

Do not fool with the R&B Drive settings as they require a scope and colorimeter.

Let us know what you find.


Terry
 

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Looks like they beat me to it, but I'd also say your G2 is set to high.

Calibrate G2, and I myself don't see any reason you can't adjust "Drive Control" after your done with G2, it's just the adjustment for the white end of grayscale, and is not a scoped adjustment.

If you don't have a colorimeter, you can throw up a grayscale test pattern, it'll have all ten ire steps in vertical bars across your screen. (the XG has one of these built in called "Grayscale")

After you do G2 all your low end "Ref White" settings should be close, however once you start doing grayscale, you may have to tweak the "Bright Bias" a little. If so remember to check the TP voltages at 7404, 7504, and 7604 as they will have changed, then adjust "Black Bias" to bring the effected one (s) back to 2.5 vdc +/- .1.

Remember "bright Bias" effects the black/gray end of the scale..."Drive Control" effects the white end of the scale.

What you do to one effects the other. (example: Increase Bright Bias on red, red's Drive Control will increase also)

Also remember, once G2 is cal'ed, DO NOT change adjustments on the Green gun, you will now adjust the red & blue around green. In fact your "Drive Control" adjustment only has adjustment for two guns, and green is not one of them :)

You can do a fair grayscale cal with your eyes, if you have access to a colorimeter even better. If you want access to one, send me a pm.
 

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Discussion Starter · #9 ·
Hey Tom, Terry, Kenny


You guys are TOTALLY on the ball.

The reason the rasters are lit up so grossly in the pic:

1. I have contrast all the way down and brightness way up... to exaggerate this effect so that I can photograph it. It IS present at normal settings but it is more subtle.

(I should have disclosed this, but I didn't want to muddy things)

Before posting these pics, I completed the KennyG/Kuo G2 procedure for the second time. Voltages are spot-on (see attachment) and the picture shadow details looks excellent. In doing the G2 I coud have erred slightly on the side of leaving Black Bias slightly high which may account for this.

However, this effect had also been appearing:

When I first got the PJ, before I did anything; and

After an EEPROM re-initialization and performing the KennyG/Kuo G2 the first time.


Tom,

My hand doesn't cast a shadow on the screen (at normal brightness and contrast settings) although there is an exceedingly faint illumination beyond the screen area within the boundaries of the rasters. I will go through a more conscientious KennyG/Kuo G2 and check this again.

At lower resolutions, the effect is less apparent, and seems to take on a slightly different pattern. (When I'm home later, I will take snap a few more shots to capture its precise character at different resolutions and picture settings)


Terry,

I will do a more conscientious KennyG/Kuo G2 when I get home later. As, you've gathered, too late to advise me not to mess the R&B drive settings... (so I get to follow KennyG's advice now) Before taking any more pics, I will do the G2 and set R&B drive control for a proper grayscale as good as I can do by eye. Then, I'll assess the weird raster lighting issue again.


Thanks, you guys are great.
 

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If your G2 has been cal'ed then I wouldn't worry about it, once you turn the Brightness down it's not very noticeable...if at all, right?

This is pretty standard with most pj's, when you have the brightness up that high, the gun is simply not turning off during it's blanking phase (return to the other side of the raster) If you start using the remote control's "Left & Right Blanking" you will notice that whole mess disappear.

If it's not noticable at normal brightness and contrast (or barely) then don't worry about it, alot of pj's have a small amount of this.
 

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It's not noticeable with contrast/brightness set to normal values? oh! Then Kenny's right. I had the same thing with an XG I had here for a month or so... when I cranked up the brightness it almost looked like the raster wasn't being blanked during the retrace. It worried me at first but then I realized that it wasn't noticeable during normal viewing settings of contrast/brightness.


Kal
 

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Discussion Starter · #12 ·
Thanks Kenny...


Blanking controls? That's yet another area to explore that never occurred to me.


NEC defaults leave blanking completely open and I always thought it was just for people who couldn't figure out how to match thier active image area to the borders of their screens!


I'll try that too...and then another assessment.
 

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I had the exact same thing with my XG -- it was subtle but noticeable during normal use (in dark or black scenes), but looked exactly like your pictures when adjusting the brightness & contrast to look into the tubes. Needless to say, Terry came over, adjusted those reference settings he mentioned, and now the problem is just GONE.


Brent
 

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Just out of curiosty shrink the raster a bit horizontally in size and then move to the left...

It almost looks like the raster is reacting to the right side of the tube....weird


Mark
 

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Discussion Starter · #16 ·
Very encouraging Brent.


I will try to get the G2 nailed down precisely where it should be. The procedure is not very difficult, but sometimes the judgment calls when doing it by eye are pretty close (i.e. one or two clicks higher? lower?)


Mark, you've given me yet another thing to think about. My Raster size is up a bit over 90% and this effect may diminish somewhat at a lower amplitude (narrower raster). Perhaps I could use Powerstrip (front and back porch settings?) to enlarge the image area in a narrower raster.

note to self: stop off at grocery for powerbars, cancel all plans for this evening, plan on calling in sick tommorrow.
 

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I think the raster usage is fine. Your making great use of the available phosphor area.


I agree with the previous diagnosis in this thread.. G2 levels seem a bit high.
 

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Dont try anything fancy just take a few seconds to shrink it horizontally on the remote...

If Iam wrong you will know in seconds ,and onto the G2 business, If Iam right you be finished


Ya dig it (lol!)


Mark
 

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David,


Actually I didn't tell you the whole story as I really don't want to try and support the other settings I did to Brents machine (and do to any I setup for customers or units I sell) that may have contributed to what you and he were seeing on the rasters.

Some time ago I was doing a reference setup on an XG in my shop and was a bit perplexed as to why I couldn't get the rasters to light the way I wanted. I had also seen this on machines in the field that had HD inputs and I could get a good grey scale on the HTPC or scaler/DVD, but the blacks would be crushed for the HD. I had to find an answer for this.

So I did some digging and read and re-read the service manuals procedures on how some of the pots in the machine were supposed to be set and their methodology was good but there had to be a better way, inputting things I know. I spent almost a week straight and went after a method to adjust the pedistal, R, G & B drive (R & B are software, G is a pot), the bias pots and the level pot to produce a satisfactory picture with great black details. All of the above mentioned adjustments are done with a scope, and then the drive is tweaked if needed with a colorimeter. After all this is done using Guy's well written method for the reference controls finishes the adjustments.

What I found quite interesting is the number of machines that I know were never touched by anyone but the factory and they were not adjusted exactly right. And as Bret indicates it does make a difference, especially when you have an HD input that doesn't give you any overlay controls for brightness or contrast.


So in my opinion, it's more than the G2 or reference settings that will make these XG's really sing. But what has to be done really should be done by a competitent tech who is familiar with the XG.


Terry
 

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In fact you should be using the pj's blanking feature...the way to set it up is for the picture to overscan the screen by about an inch on each side...then blank all four sides to the viewing edge of the screen.


If all of your rasters are setting just as that green shot, then you are making good use of your tube face.
 
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