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Old 06-03-2013, 07:03 PM - Thread Starter
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I have a Samsung 64D7000. The original panel was replaced because of a peeling screen filter. This new panel has a screen uniformity problem that I described in the thread entitled "Green Blob back again for 2013!" I did not supply a link because the thread, even though it is not apparent by its title, is for Panasonic ST60 models. However, in that thread, before I realized its purpose, I did describe the problem and quote it here:
Quote:
...on my panel there is a smooth pink relatively narrow vertical amorphous area on the left. Moving to the right, there is a wide vertical amorphous greenish area followed by a narrow pink one followed by a wide greenish one followed by a very prominent pink area. The areas are almost from top to bottom on the screen.

It is not caused by sub-pixel not firing. It is very similar to what I had on my Panasonic px80u. It is very annoying while watching B/W movies -- with the color control at zero.

In addition, the uniformity problem is a function of screen content. When a full screen gray or white pattern is displayed, the issue is very evident. However, if a black box of about 20% (or greater) is inserted anywhere on the screen, the uniformity improves and the problem is barely visible. That makes it not very intrusive, if at all, when viewing normal content. It is more annoying with black and white content especially with low APL.

Today I checked the Vs and Va voltages on the power supply and found them almost exactly as specified by the sticker on the panel. Vs was 217.3 (sticker is 217) and Va was 55.8 (sticker is 55.) Increasing these to 219 and 57 respectively seems to improve the situation -- but far from enough.

I did increase and decrease both voltages for the available range of the control for a few minutes and saw no improvement -- some slight change but no real improvement.

Any help would be appreciated.


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Old 06-04-2013, 07:35 AM
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No consolation but I have a very similar sounding problem on my E7000. Noticeable uniformity problem with large vertical pink areas in some light scenes. I see it with solid white and light grey test slides, and also very annoying watching hockey particularly when panning across the ice. Input source makes no difference, and calibration settings have little effect. As you say it's subtle enough that in most content it's not visible at all, but in other scenes it's very distracting. I've had 3 panels and two main boards replaced, and the voltages checked twice, with no improvement. Geek Squad guys worked with Samsung, but eventually just gave up and said they couldn't fix it. Still no idea if I'm just unlucky, or if it's a widespread issue that most people don't notice. I'm now in the process of looking for another model TV.
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Old 06-04-2013, 02:21 PM - Thread Starter
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I did some further investigating last night. I found that the higher value of Va caused faint vertical banding that were very visible during 20 and 30% full screen grayscale displays. Lowering Va back to its original value of 55.8v reduced the banding to nearly being imperceptible.

Also, I found that reducing Vs causes the full screen to become pinkish and that for my panel a value of 220v (sticker value 217) was the optimum.

I examined the effect of changing the Vscn on the Y scan board. Lowering it down to -210v (sticker value -197) caused pixel misfiring. Increasing it to about -185 increased the intensity of the green tinted blobs and caused severe graininess in the greenish area on the left side of the screen. Decreasing the voltage from this point seems to have improved the overall picture but certainly not by much. I did not measure the voltage where the control was left.

From the underwhelming response to this thread, I assume that I am not going to receive any useful help. But I thank those of you that have taken the time to read about my plight and endeavors. Guess its back to plan A and put the set up for sale. Since the picture looks fine at my normal output intensity (which is only about 30 ftL), I doubt that most buyers would ever see the problem and be very happy with their purchase.

Sorry for your situation too, abalone.

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Old 06-04-2013, 02:40 PM
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Seriously, do not tweak Va. You run the risk of frying the plasma panel. Vertical bands are signs the panel drivers are being stressed and damage is possible, which is not repairable without a third panel swap.

Aside from that, tweak away.
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Old 06-04-2013, 02:45 PM - Thread Starter
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Thanks, Tom. I knew that and that's the reason that I only changed it by 2% max -- from 55.8 to 57. It is back down to the original voltage.


Just a clarification: I knew that Va can cause serious problems. I did not know that the banding was the indication that the danger zone had been entered. smile.gif

edit2: I just measured Va again. I had left it at 54.6 v last night. Close enough to the the specified 55v on the sticker. On another aspect of this adjustment: it opens the possibility that one can brick the TV on purpose and get a replacement panel -- if one has an extended warranty and takes care to put the potentiometer back to its proper position after the damage is done. Not that I would do this or even suggest that one does it. biggrin.gif

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Old 06-04-2013, 03:24 PM
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Originally Posted by LarryInRI View Post

Guess its back to plan A and put the set up for sale. Since the picture looks fine at my normal output intensity (which is only about 30 ftL), I doubt that most buyers would ever see the problem and be very happy with their purchase.

Good reason to upgrade, what's your next one gonna be, ultra-black or ultra-white?
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Old 06-04-2013, 03:32 PM - Thread Starter
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Good reason to upgrade, what's your next one gonna be, ultra-black or ultra-white?

Therein lies my dilemma. Depending on the time of day or the phase of the moon, my choice changes. If I can be convinced that the F8500 can be tamed without causing problems, that would be my choice. Otherwise the VT60 is tempting but the tricky calibration controls on it are disconcerting. The reason that I decided to play with this set and attempt to make it more acceptable was to eliminate this frustration of choice and not buy a new one this year.

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Old 06-04-2013, 03:32 PM
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Larry, I don't see the problem occurring immediately. The pot probably only goes up to 58~60V. The panel would likely run months with that, including with the banding. It would eventually get a single stuck vertical line, a driver failure (black or white bar sometimes with lines about 1/15th width of display) or a complete failure to show any image (due to shorted Va.) And dealing with Samsung customer service is russian roulette. Maybe the tech comes out and swaps the panel due to the bars. But maybe he decides to swap every other board beforehand... he ain't paying for those boards.
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Old 06-04-2013, 03:40 PM - Thread Starter
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Larry, I don't see the problem occurring immediately. The pot probably only goes up to 58~60V. The panel would likely run months with that, including with the banding. It would eventually get a single stuck vertical line, a driver failure (black or white bar sometimes with lines about 1/15th width of display) or a complete failure to show any image (due to shorted Va.) And dealing with Samsung customer service is russian roulette. Maybe the tech comes out and swaps the panel due to the bars. But maybe he decides to swap every other board beforehand... he ain't paying for those boards.

Shorting Va should be a trivial task -- again only for those that want to. wink.gif

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Old 06-04-2013, 04:48 PM
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Quote:
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Quote:
Originally Posted by zoyd View Post

Good reason to upgrade, what's your next one gonna be, ultra-black or ultra-white?

Therein lies my dilemma. Depending on the time of day or the phase of the moon, my choice changes. If I can be convinced that the F8500 can be tamed without causing problems, that would be my choice. Otherwise the VT60 is tempting but the tricky calibration controls on it are disconcerting. The reason that I decided to play with this set and attempt to make it more acceptable was to eliminate this frustration of choice and not buy a new one this year.

Larry

I hear ya, if I were buying (which I'm not) I'd demo the VT60 for a couple three weeks because I know what the 8500 will look like, and then exchange it if not happy. The ZT60 is a marketing gimmick.
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