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Discussion Starter · #1 ·
Good Morning Gentlemen.


I was recently adjusting focus on my 45" RPTV and noticed something. The screen has a bit of inward bow which is causing the Corners and outside edges between the corners to be less focused than the center of the screen.


Do the Mits RPTV's allow for adjusting the focus on the corners and the midpoint of the outside edges.


And if so what are the labels for these settings in the Service menus.


I have the codes for getting into the service menus and use them frequently to set fine convergence. But I am not clear on what settings control the corner and midpoint focus.


Thanks for any suggestions.


eric.
 

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I'm not an expert but I've doing a lot of reading of service tips in the last year. I've never heard of anything other than electrical and manual lens focusing. All use the screen center point as the focal point. I would think that if your screen is concaved that is what has to be corrected. Post the make and model of your RPTV, maybe someone has more specific info.
 

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Discussion Starter · #3 ·
The make & model is a Mitsubishi VS-4544 from 1996. 4:3 aspect with Delta 77 lenses or guns.


I did a full-on manual & electrostatic focus along with a geometry & convergence calibration which helped a little. But the way the screen hangs, I can do nothing about the concavity of the screen. The depth of the concavity is only about 1/2" MAX.


I saw a bunch of settings like : D40, D42, D50, D52 which had a range of 0 - 255 which appeared to have no effect on the screen so I left them at the default 127 value. But I hae seen alot of Front projectors with the ability to

adjust the corner & mid-edge focus so I thought my big screen may have that ability also.


It is not a MAJOR issue since watching DVD in widescreen eliminates 6 of the 8 "less than focused" spots. However there is some minor red, green & blue blooming and loss of focus , when watching 4:3 material that I would like to minimize or eliminate.


thanks anyways Zignif. I may just be S.O.L. with this set
 

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Untie someone who really knows what they are talking about, jumps in,,,,,,,


I would think that the additional adjustments that front projectors have, would be mechanical in the respect that all edges of the CRT need to be be square to the lens assembly. They probably also use dynamic beam shaping, which may be the reason that FP's take a lot of work to align.


Blooming is caused by the high voltage power supply's inability to maintain the proper voltage during heavy load. It should disappear when the brightness and contrast are reduced. This happens when these controls are turned up to compensate for aging phosphors. Naturally, blooming destroys focus. There are other causes for blooming but this is the most common.


I don't know why your screen is sagging unless you did a re-stack. I read where one fellow had that after he re-stacked. His solution was to secure the top, have someone hold it upright while gravity pulled it down, secure the bottom, then re-install the screen. I would think that with the huge reflection angles of RP's this would make a big difference in center to edge alignment. I don't know, just guessing.


Have you been to The Home Theater Spot? http://www.***************.com/cgi-b...nt=;DaysPrune=

They have a Mitsi specific area. Like this one, it is a very good site.


Good luck.


Dick
 

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Discussion Starter · #6 ·
Zignif This problem is not a "Contrast caused" blooming issue. The Red blooms in one corner and the Blue blooms in the other corner.


I do know the previous owner pulled the screens out to clean them before having it delieverd to me. I will check to make sure they are hung properly. That could very well be the fix I need.



And thanks for the

http://www.keohi.com/keohihdtv/exper...antilever.html


Link. But I have already run through this process. So I think the re-hang will be the best approach for now.


thanks.


eric.
 

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Hmmm, Red in one corner, blue in the other..... If not very poor convergence, then is has to be an optical problem.


Just a thought, when you have the screen off, check that the mirror is seated properly. Could it have been removed, cleaned and not put back correctly?


Let us know what happens.


Dick
 

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Please state the model of your TV. This sounds like it is an older analog set without the now standard 64-pt Mits convergence. What is your current overscan? You may have to reduce this to better converge your corners.
 

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The blue and red blooming at the upper corners is normal to a degree. The upper left corner is the frathest point from the blue gun (if the blue gun is on the right) and the upper right corner is the farthest from the red gun. Short of messing with the mechanical focus (which I think you've done already) there's not a heck of alot you can do. You can try removing the screen to get at the CRT's in case they need cleaning (good possibility with a 6 yr. +/- old set), but other than that, there's not much you can do. You could also check to see if your TV has mechanical edge focus adjustments.


Rob
 

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Though mentioned already, you might check in at the Spot and ask one of the calibrators who post there if they have any ideas. (there are two calibrator related forums, one for users). I am no expert but it sounds like a mechanical thing... the sag is a major component of the problem and perhaps not easily fixed. -- Bruce
 

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Discussion Starter · #12 ·
Well part of the problem is what I can see when looking into the gun (with the level turned down , of course!)


The image all 3 guns are firing seems to be off center. I will try to explain.


The whole image is shifted over ( probably 20 pixels or so) so that the left side of the image is "bouncing" off the inside of the CRT and polluting the screen with reflected light. I can se the pollution as red, green or blue "static" on the screen (depending on which color is most predominant on the screen).


This "bouncing" effect is causing the Blue blooming that I thought was a focus / screen issue. It is a bit of a problem with the Green & Red but not as severe.


Zignif - I check the mirror every time I clean it, the lenses and the CRT faces under the lenses. I live in a VERY VERY dusty part of sothern California so I have to clean them every 3 months or so.


Talons55 - yeah I knew some slight loss of focus was to be expected in the extreme corners. but this is way beyond normal. I am talking like up to 1/4"

of "bloom" on each side of the Green line. But only on the Blue corner now.


I got the Red minimized to an tolerable level by looking in the gun and doing an Electrostatic focus THEN putting the screen on for a mechanical focus.


Now I just have to figure out how to Re-center the image in the CRT so it does not "bounce" off the inside of the CRT.


and thanks guys. it is helping to talk my way through this.


/me wanders off muttering "Galdarn bouncing friggin' fracking CRT rootin' tootin' varment!"
 

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Getting close I think. CRT's have centering magnets on the neck of the tube, just below the deflection yoke. It sounds like these have been moved.


My serv. manual says to display the single large convergence cross, then adjust the magnets to position it in the center of the screen. If your set doesn't have this cross, you will have find something else to determine the center.


You have to get all 3 to converge at the center. You will then have to do your normal convergence. I'm sure it will be way off, after centering the raster.
 

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Discussion Starter · #14 ·
Well the move was kinda bumpy and ruff (in the back of a U-Haul through town) so mabye the deflection yolks got jostled around more than I initially thought.


Avia has a fullscreen centering Cross with Corner guides. So I will have to use this and eyeball the position till the color polluting and "bouncing" off the CRT walls is minimized on the raster adjustment.


thx again Zig.


eric
 
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