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Discussion Starter · #1 ·
Not long ago, I posted a small, but irritating problem that I was having with my Panasonic Tau CT-34WX50. At the time, I explained the issue as probably being related to the geometry on the set. The reason was mainly because the results of the problem made it look as though vertical lines and text were bending or slanting on certain areas of the screen.


After investigating this again recently, I’m now starting to have a different theory about what might be occurring and I’d like some input on what all of you think. I want to know if I need to get an ISF to calibrate my set and maybe fix this, or if a Panasonic service tech could fix it.


First of all, let me recap exactly when the problem occurs. It ONLY happens on either of the 2 component inputs when running both 480P or 1080i signals. It DOES NOT happen when running anything in 480i (or using the line-doubler).


Here’s a perfect example of the issue……


I was recently watching the Little Women opera in HD on PBS-DT. At the end of the show, they were interviewing one of the actors as the credits were rolling up the screen on the right. The actor was on the left of the credits and the background was black.


As the white text of the credits rolled up, I looked at the guy on the left of the screen and noticed his face and body looked like it had faint ripples running through it. Those ripples were the effects of the credits rolling on the right. It was not too bad unless you looked for it, but I know it’s there. And I’ve come to figure out that this has to be the root of my suspected geometry issues.


Now to me, this seems like some sort of “ghosting†or “smearing†problem. Could this be the result of a bad power supply? Is the tube just bad? Are my component inputs bad when using a high bandwidth signal?


I’ve tried many different picture settings and nothing helps this, even if Contrast is at it’s lowest.


Another prime example could be this…If there is a single vertical line (any color) running down one side of the screen against a solid background (any color) and then there is some text at different areas on the screen…it causes the vertical line to bend/protrude out at certain points where the text is horizontally located on the screen. Does this make sense? I wish I had a picture of all this. It’s like the text creates a horizontal ghost trail that extends across the entire screen!


This has come to be quite irritating when trying to watch HD or DVD because the rest of the picture is awesome, especially HD material. And in normal viewing of a movie or program, it’s not noticeable. But the second that graphics are displayed, such as in a DVD menu, or when credit roll, or subtitles are displayed, it’s quite noticeable.


My big question is…does anybody know what this indicates? If so, can it be fixed easily, or will I have to exchange my TV for another to get it fixed? It’s been this way since I first got the TV back in January, I’ve just lived with it.


I’ve seen this same problem on computer monitors before, but it never seemed to be bad enough to affect the geometry of text and graphics on the screen.


Any help or suggestions are welcome.


Thanks,

Eric

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I've seen this happen on my Panasonic 47WX49. I think it has something to do with the "long retrace". I see this mentioned about DTC-100, and Panasonic displays frequently, especially in reference to transcoders. KeyData even has a "special sync" switch on their transcoder in order to deal with this. I've tried to find information about this but my internet searches have thus far been in vain. I too would appreciate any info regarding this. A definition wouldn't hurt either. If someone knows, is this the amount of time that it takes the scanning beam to go from the end of a line, to the beginning of the next line to be scanned?
 

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Discussion Starter · #3 ·
Yes, I agree. A definition from somebody "in the know" wouldn't hurt. This can't be a very uncommon problem. As soon as I can, I'm going to try and get some example screenshots up so anyone can take a look and see exactly what I'm talking about. I've searched all the A/V forums too, and haven't been able to find anyone with this same problem or get any answers from anyone.


BTW, just so everyone knows. This isn't just a problem with my RGB-to-Component transcoder (Audio Authority). Yes, it happens when running my pc desktop through it at all resolutions (mostly 960x540P), but it also happens when my Pioneer DV-37 is set to progressive mode and when I run the 1080i signal from my DST3000 HD receiver. Even my older Toshiba 5109 progressive player causes it too!


So what I'm saying is that it can't be just one faulty external component causing this. It has to be a problem with th TV itself. UNLESS, God forbid, all those components are incompatible with this TV!


I'll have some screenshots soon....


Eric

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From the "Video Essentials" website:


Vertical Blanking (Retrace) The process of bringing the scanning electron beam in a CRT from the bottom of the picture back up to the top of the picture. Vertical retrace occurs between writing each field of a picture. The beam is shut off, blanked, during the retrace period. About 92% of the frame period is spent writing active horizontal lines.

The remaining 8% is spent on vertical retrace.


Can somebody answer, what happens when the time spent in this state is long? Can sync on any of the previously scanned lines appear to be lost?
 

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Eric, I also own the exact same set. I have not seen any problem like this. It looks like your gain is to high causing a blooming effect. Have you tried backing down the brightness? There is a different setup for each input. My 480i input material is *darker* than my 1080i material so I had to increase my brightness on the 480i inputs but decrease it on my 1080i stuff. Only other suggestion is a grounding problem. Check all your equipment and make sure it is on the same ground. I've seen grounding problems cause tearing on digital sets.

Good luck.
 

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Hello,


I have had this problem on my CT-32XF56, and after extensive messing about in the service menu and trying to interpret what each adjustment in the service manual actually did, I was able to correct it. While this is not the same set, I would suggest that the following same adjustments are offered on your set. On my set (which only does 480i and 480p), there are separate geometry adjustments for 4x3 and widescreen, while on your set I imagine there are independent settings for 480i vs 480p/1080i.


Within the geometry adjustment section of the service mode menus there are two adjustments for the horizontal size of the image, the first one (I don't have the manual handy) adjusts the overall width of the picture and has a range of about 0-64. I believe it is labeled something like "H-SIZE" or horizontal size. There is another item (I believe called) EHT (very intuitive!), which has a range of 0-7. I couldn't figure out what this did other then also (slightly) adjust the horizontal size while changing it when viewing a test pattern of dots - until I happened to have the AVIA overscan screen that switches between black on white to white on black displayed. It became apparent that this setting allows you to set an offset in screen width for all-black, verses all-white images, making up for the power supply sag that causes the location of fixed image elements to change when the brightness of another area of the image changes. So as the the test pattern changes from white on black to black on white, you can adjust this setting and get the two images to be the same width (mine were way off initially). Also note that a change of 1 or 2 makes a huge difference. After I made this adjustment, the problem you described was gone. Please note, doing this without a service manual is just asking for trouble, so either order it, or have a tech (forget about the Panasonic techs, they wont help) adjust it.


Best Regards,


Alex Hirsbrunner
 

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Discussion Starter · #8 ·
Thanks Alex! Your suggestion is the best help I’ve received on this issue as of yet. Actually, I had the CT32XF55 (the first model) that came out in 1998 before the “56†model came out. Although it never exhibited that problem I did make many service menu adjustments on it and I do remember that EHT item. When I bought the Tau, I gave the CT32XF55 to my parents.


That said, you may be right about this being the root of my problem. The only thing I’m afraid of is that I can’t adjust it in the CT34WX50 menu. I have the service manual for it and I’ve already been in the menu several times to make geometry adjustments. As a matter of fact, I’ve already tweaked the geometry as good as I can. Believe it or not, the horizontal and vertical geometry for both 480i and 480P/1080i is as actually quite good (when this distortion problem is not visible).


Of all the adjustments made available in the Tau service menu, I haven’t seen anything called EHT. To me, the Tau service menu is even more difficult to navigate than the CT32XF56. There are definitely less options available for adjustment in the Tau menu.


I will look at this again tonight and see if I can find it, but I’m 99% sure it isn’t available.


To the poster who suggested it might be a gain problem…it’s not. Even if I turn Contrast all the way down and turn brightness all the way down to where I can hardly see anything on screen, I can still see the distortions.


You’re right about the Panasonic techs. I’m certain that if I had one come out and look at it, all he’d say is “Sorry, I can’t fix it here…I’ll have to take it into the shop, or we’ll just send you another TVâ€. And I’m not sure that I want to risk getting another TV that would probably have some other issue. That’s why I’ve learned to live with this because there is no perfect TV; they’ve all got issues. It all depends on what issues are really noticeable to you and if you can live with them.


Thanks,

Eric

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Looks like a power supply regulation problem. Can be caused by "pushing" the adjustments (like trying to get a picture that's brighter than it was designed for), or it could just be defective. In any case, it is not acceptable.
 
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