Plasma TV has line across that normal? [Archive] - Audio & Video Forums


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01-31-2006, 09:43 PM
I just bought a Panasonic TH-42PX50U plasma about two weeks ago and I was running the DVE video test and noticed a line across the middle of the screen when I run tests with a constant color across the screen. It is hard to tell if the top half is darker than the bottom half or if there is actually a lighter color line running across the whole image. Is this normal or should I take the TV back?

02-01-2006, 07:17 AM
A few things spring to mind. Let's try one thing first. Turn everything off. If you have a cable box, unplug it, and then run a test image from DVE? Is the line still there? If not, the cable box is creating a grounding problem. Either isolate the cable ground, or watch all DVDs with the cable box unplugged. If so, continue troubleshooting.

Do you ever notice this line when you're watching another DVD? Is it the kind of thing that you'd see if you looked closely on the background of the scrolling titles at the end of a film or in an image with a deep blue sky or some other uniform color or dark area? If you can't find it on typical DVD viewing material, in addition to DVE test screens, it doesn't necessarily mean that the artifact isn't there, but it does mollify it somewhat. Nonetheless, it's an artifact that shouldn't be there.

My initial reaction is that it doesn't come from the Panasonic, unless your DVD player doesn't have progressive scanning ability. If it doesn't, the Panasonic will be responsible for the processing, and it might not be too good at it. But if your DVD player is progressive, and you've been using it that way, send the signal to the panel as interlaced instead and let the Panasonic do the work. Does this change anything? If your progressive DVD player suffers from the Chroma Upsampling Error (CUE), you'd get color bands but not just one. Check whether smaller color patches show horizontal banding or a combing effect along diagonal lines. You might have to get close to the screen and/or check online to find out whether your DVD player has CUE. If you don't have a progressive-scan DVD player, borrow or "buy" one or two from Circuit City or some other store with a liberal return policy. If relieving the Panasonic from the burden of deinterlacing removes the problem, keep the player.

Do you ever notice this line on other types of material, like cable broadcasts? Is it present on hi def feeds or only 480 or SD feeds? How does your cable box handle 480 material? Does it send a progressive or interlaced signal? If interlaced, then again the Panasonic will have to deinterlace it by itself. Set the cable box to send 480p instead, if possible, to see whether the line goes away. If so, you may have located the source of the error. If not, and the DVD player gambit hasn't accomplished anything either, it's back to the drawing board. Something may, in fact, be amiss with the plasma.

I hope the problem turns out to be simple to correct.

02-01-2006, 02:07 PM
I've found that it is a lighter color line across the exact middle of the screen. I notice it the most with a grey background color. I see it on the DVE test screens that contain greyish color across the whole screen. I first noticed it watching my HDTV cable box when I press menu. The menu shows up 4:3 and on the sides of the screen are grey bars, when I choose a channel the whole screen goes grey intermitenly and then I notice the line across the screen. When watching the DVE intro and the space shuttle is flying through the blue air I also see the line. It is basically a strip of a more washed out color of whatever is on the screen. I have tried all outputs from my HDTV box 480i, 480p, 720P and 1080i all in component. My DVD player isn't progressive scan but I have tried Svideo and Component. In all cases I still see the line. However, it was much less visible with the default picture settings. It was after I configured the Plasma with the DVE that I noticed it more. When the screen is brighter I can't see it as easily. It is a bad line, I really only see it on constant color backgrounds. During normal viewing you can't find it if your looking for it. My friend says I am way too picky, but I like my stuff perfect. Circuit city in all of Southern California is apparently sold out of these. They said I can bring in my reciept and then when they get them in they will deliever the new one and take back the old one for a 50 buck delievery charge (I orignally picked it up in store). I know with my Trinitron monitor the vertical lines are normal to help stablize the picture and thought maybe this was the same type of deal.

02-01-2006, 08:01 PM
Well, I guess you have nothing to lose, except $50.00. The brighter screen before DVE calibration masked the line; it didn't prevent it. For curiosity's sake, I would like to have found out whether the line showed up with a progressive scan DVD player, even though the plasma would still have some scaling to do. But the fact that the line presumably looked the same whatever you threw at the screen doesn't bode well for the Panasonic.