[jailonacs99]

I've had my 42" Panasonic TH-42PX50U for about 3 years now, and over the course of the last couple of months have noticed a clear brightness division running horizontally through the middle of the panel, with black levels noticeable lighter on the bottom half.


The issue is only really clear during darker scenes in movies, and even then only depending on the type of dark/black scene being shown. If there is no picture on the screen and it's just black, then the difference is quite stark. If the scenes have a lot of color though or are bright, you can't tell at all.


Is a plasma panel usually composed of two separate displays one on top of the other, and is the bottom one aging or fading faster than the top for some reason? Is this some kind of screen failure? Can I expect it to get worse?

 

[mpcengineering]

That sounds odd to me, it across all inputs and multiple input devices?

 

[sharpbandaid]

Sounds like double scan issue. Your pdp's bottom and top half is driven with two separate circuits. These circuits might have slightly drifted that causes this problem.

 

[RandyWalters]



Quote:
Originally Posted by jailonacs99 /forum/post/15437195


I've had my 42" Panasonic TH-42PX50U for about 3 years now, and over the course of the last couple of months have noticed a clear brightness division running horizontally through the middle of the panel, with black levels noticeable lighter on the bottom half.


The issue is only really clear during darker scenes in movies, and even then only depending on the type of dark/black scene being shown. If there is no picture on the screen and it's just black, then the difference is quite stark. If the scenes have a lot of color though or are bright, you can't tell at all.


Is a plasma panel usually composed of two separate displays one on top of the other, and is the bottom one aging or fading faster than the top for some reason? Is this some kind of screen failure? Can I expect it to get worse?

I have the exact same TV and like your TV, the black levels on the lower half of my screen are noticeably lighter than the upper half. It's been this way as long as i can remember and has not gotten any worse over the years. Like yours, it's only visible on a blank input or when changing inputs, and i sometimes see it on very dark scenes but otherwise it's not an issue. My friend's larger 50PX50U does the same thing, but i think his upper half is brighter IIRC.


The plasma panel isn't composed of two separate displays, it's just one big one-piece panel so it's not a problem with the panel. There is a video board that drives the upper half of the panel and another video board that drives the lower half so it appears to just be a tolerance difference between the upper and lower video boards. I just try to ignore it when i see it

My newer 42PZ700U however does not display this effect - the upper and lower halves of the screen are identical and i cannot see any difference in brightness between the two. Maybe Panasonic added some kind of circuitry to the newer models to maintain equal brightness. Dunno.

 

[sharpbandaid]



Quote:
Originally Posted by RandyWalters /forum/post/15437452


My newer 42PZ700U however does not display this effect - the upper and lower halves of the screen are identical and i cannot see any difference in brightness between the two. Maybe Panasonic added some kind of circuitry to the newer models to maintain equal brightness. Dunno.

Many new pdps use single scan method that uses the same circuit to drive the whole panel.

 

[jailonacs99]

Excellent guys, thanks for the info. Ya, it's not much more than a nuisance at this point, I was mostly just concerned that the problem would get worse since it only really appeared in the last several weeks. If it's static, I can put up with it.


With plasma prices the way they are now though, I may not be able to wait long to get a 50" 1080P! Incredible the Panny's are selling for $1500 or so when, 3 years ago I spent weeks shopping around just to find someone with my model in stock for over $2K!!!