# Panasonic 12G Panel Black Level Rising



## Gov (Nov 21, 2007)

I have began reading about problems that people have reportedly developed with the Panasonic 12G panels. The problem is that on these panels the black levels are rising after a certain amount of hours on the sets. Below is something I copied and pasted, it is some Panasonic patent information which is reportedly a voltage increase that is to blame for the gradual rise in black levels with these panels. There is a growing active thread on it over at AVS right now. People are saying that they noticed it and confirmed their suspicion by actually measuring the rise. 
http://www.avsforum.com/avs-vb/showthread.php?t=1167339

_Next, the relationship between the power-on accumulated time and initializing voltage Vr is described. FIG. 13 is a pattern diagram showing the relationship between the power-on accumulated time and discharge start voltage of panel 10 of exemplary embodiment 2 of the present invention. As the power-on accumulated time of panel 10 increases, the discharge start voltage gradually increases . The discharge characteristics vary over time, so that the following problems occur. When initializing voltage Vr is set with reference to the discharge start voltage of panel 10 having a short power-on accumulated time, extending the power-on accumulated time increases the discharge start voltage. At this time, initializing voltage Vr becomes relatively low with respect to the discharge start voltage, hence the initializing discharge becomes weak, and sufficient wall voltage cannot be generated or the priming runs short. Thus, the initializing discharge can be insufficient. While, when initializing voltage Vr is previously set to be high in expectation of the variation over time of the discharge characteristics, initializing discharge becomes stronger than necessary in panel 10 having a short power-on accumulated time, light emission that is not related to the image display becomes strong, the black luminance increases, and the contrast can degrade. 

However, the panel of the present embodiment has accumulated time measuring circuit 83, measures the power-on accumulated time, and performs control so that initializing voltage Vr increases with extension in power-on accumulated time. An image with sharp contrast can be displayed without un-stabilizing the initializing discharge regardless of the power-on accumulated time from the initial stage of the manufacturing of plasma display device 1. 

An example of the method of controlling initializing voltage Vr based on the power-on accumulated time is a method of continuously increasing initializing voltage Vr with extension in power-on accumulated time. In the present embodiment, a plurality of accumulated time thresholds are set, the power-on accumulated time supplied from accumulated time measuring circuit 83 is compared with the accumulated time thresholds, and initializing voltage Vr is increased whenever the power-on accumulated time exceeds the accumulated time thresholds. FIG. 14A and FIG. 14B show a control method of the initializing voltage and a transition of the contrast ratio in accordance with exemplary embodiment 2. FIG. 14A shows the relationship between the power-on accumulated time and initializing voltage Vr, and FIG. 14B shows the relationship between the power-on accumulated time and the contrast ratio. In exemplary embodiment 2, three accumulated time thresholds of 650 hours, 850 hours, and 1000 hours are set, and initializing voltage Vr is increased by 5 (V) when the power-on accumulated time exceeds 650 hours. The increase in initializing voltage is performed not only in normal-temperature driving mode but also in low-temperature driving mode and high-temperature driving mode, and regardless of the APL value. When the power-on accumulated time exceeds 850 hours, initializing voltage Vr is further increased by 5 (V). When the power-on accumulated time exceeds 1000 hours, initializing voltage Vr is further increased by 5 (V). 

In the present embodiment, as the discharge start voltage is increased in response to extension in power-on accumulated time, initializing voltage Vr is increased. Therefore, image display with a contrast stabilized at a high level is allowed regardless of the power-on accumulated time. 


It is considered that the panel is hardly affected by increase over time in discharge start voltage when initializing voltage Vr is high, so that increase rate of the initializing voltage may be decreased as initializing voltage Vr becomes high. _


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## lcaillo (May 2, 2006)

As I stated in the thread at AVS, there is much that we do not know about how each manufacturer manages the panel initializing, scan, sustain, and reset voltage cycles. They just don't provide documentation in detail. I was, however, at service training for 6 manufacturers in fall of 2008 where a couple of them discussed how they have preprogrammed changes in the voltage control over the first few hundred hours, in order to account for changes in the response of the panel. I do not recall which vendors they were, but I believe that Panasonic was one of them. I have maintained for some time that there are changes in PDPs that may require careful consideration of the initializing and scan voltages to avoid low level activation noise that is common in some sets. I have measured changes in brightness and level that occur over the first few hundred hours, but I have not note a change in panel waveforms ( I was not looking for that). I have noted that some panels showed changes in low level noise over the first few hundred hours. The NEC and Fujitsu panels were easy to notice. It is not surprising to me that something like this might be going on, and I would not count on getting much solid information from Panasonic or anyone else on the matter. The tech support folks just don't know that much detail and the engineers don't release this kind of detail in most cases.

The bottom line is that the set should be able to be adjusted for similar blacks as these changes occur, either in aging of the panel, programmed changes in panel voltages, or both. If it can't, then there is a problem that needs to be dealt with at a service level. The company that I do service and calibration for mostly stopped selling Panasonic a couple of years ago other than a few applications where other products are not a god choice. I don't have specific experience with the newer sets, so I cannot comment on how they behave. I can tell you that I have measured changes in panels in the first few hundred hours, so they do change, in all brands. Some may manage that change, others may not, some may have botched their attempts to do so. It seems that there may be some variance that Panasonic has not controlled for or done poorly from the complaints that I have seen. I have not heard of any professionals making measurements of the matter, however, so it could be that the changes can be calibrated out.


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## Gov (Nov 21, 2007)

Thanks for the detailed response ^^^^ According to a couple of the posters at AVS, they have stated that this issue is NOT a matter that can be calibrated out at all. Supposedly once the "idle black level" starts it cannot be recalibrated out.
I have a 58V10 Panny with about 300 hours on it and I have done my own calibrations on it and it seems perfect so far. I do not have the means of any measurements though.
I am suspecting that there may be a firmware bug thats occurring? Some people have also said that their displays have prematurely started exhibiting a black level elevation.
This is very disappointing to me if thats the case.


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## lcaillo (May 2, 2006)

As I said, it is impossible to know what is going on based on the lack of information coming from the manufacturers and the nature of the reports from consumers. Not having heard from a pro calibrator or anyone whom I know to be reliable in making measurements, I would not assume anything at this point. The internet and forums like this are notorious for blowing things out of proportion, and this may be one of those cases. Nearly everything that I have read at AVS, and everything here so far is just hearsay and anectdote. I really don't think much intelligent comment can be made without making some measurements, both of the panel control waveforms and the output after proper calibration, before and after aging a few hundred hours. In the absense of that, report what you experience, but lets not move a speculative thread from AVS to Home Theater Shack. Report the facts and your personal experience and opinions, and let's keep it at that.


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## Gov (Nov 21, 2007)

lcaillo said:


> In the absense of that, report what you experience, but lets not move a speculative thread from AVS to Home Theater Shack. Report the facts and your personal experience and opinions, and let's keep it at that.


While I respect your opinion on this matter and several others that I have read here, I completely disagree with your above quote. Is the Home Theater Shack an elitist forum now? Look, I was just passing on what I read over at AVS to this forum because I wanted people to know of this potential problem. I also wanted to seek input from people like yourself, but your above comment is out of line in my opinion. Even if something is speculation, but very possibly true, is it not worth discussing on your forum? It is true that I have not experienced this "idle black level" on my V10, but I only have about 300 hours on it so far. Problems like this do concern me and may concern others here on the shack as well. After all, I lived through the infamous Sony "flicker" problem with two CRT RPTV's in the past 
Anyways, I appreciate your input minus that comment.

Happy New Year!


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## lcaillo (May 2, 2006)

Gov said:


> While I respect your opinion on this matter and several others that I have read here, I completely disagree with your above quote. Is the Home Theater Shack an elitist forum now? Look, I was just passing on what I read over at AVS to this forum because I wanted people to know of this potential problem. I also wanted to seek input from people like yourself, but your above comment is out of line in my opinion. Even if something is speculation, but very possibly true, is it not worth discussing on your forum? It is true that I have not experienced this "idle black level" on my V10, but I only have about 300 hours on it so far. Problems like this do concern me and may concern others here on the shack as well. After all, I lived through the infamous Sony "flicker" problem with two CRT RPTV's in the past
> Anyways, I appreciate your input minus that comment.
> 
> Happy New Year!


Did I say not to express your concern? Did I tell you that the thread would be deleted? Did I tell you that you should not have posted it? No, I did none of these. What I said was that we do not need to continue the kind of speculation that has been aired out enough elsewhere. If you have facts post them. If you have personal experience post it. If you have concerns, post them. You did so. The fact is that there is not a good answer at this point. I would love to research it more and to see some actual data from reliable sources. There is not much more to be said unless you have some additional information on the matter.


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## Gov (Nov 21, 2007)

lcaillo said:


> Did I say not to express your concern? Did I tell you that the thread would be deleted? Did I tell you that you should not have posted it? No, I did none of these. What I said was that we do not need to continue the kind of speculation that has been aired out enough elsewhere. If you have facts post them. If you have personal experience post it. If you have concerns, post them. You did so. The fact is that there is not a good answer at this point. I would love to research it more and to see some actual data from reliable sources. There is not much more to be said unless you have some additional information on the matter.


Fair enough


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## Gov (Nov 21, 2007)

Panasonic's official statement on this issue to CNET

http://news.cnet.com/8301-17938_105-10447329-1.html?part=rss&tag=feed&subj=Crave

CNET response to that statement

http://www.engadget.com/2010/02/04/panasonic-cops-to-rising-black-levels-in-its-plasma-hdtvs-but-q/

http://gizmodo.com/5464704/panasonic...s-a-good-thing

Stay tuned!


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## Gov (Nov 21, 2007)

Well it appears that Panasonic has agreed that they designed their plasma displays to increase idle black over time. They are changing the design a bit for the 2010 models saying it will "improve" this premature idle black issue. 
Fortunately my display still looks good, but I am not appreciative of Panasonic stance on this issue since they appear to be saying the display was designed this way even though some displays may have a large jump in MLL in a relative short period of time.
I have to believe from what I have read that some displays are developing this problem because of this design and feel that Panasonic should take some action in those cases. It appears that they will not be.
Here is the latest CNET reponse. 
Any input here would be greatly appreciated, thanks.

http://news.cnet.com/8301-17938_105-10449939-1.html?tag=mncol


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## lcaillo (May 2, 2006)

I think what people fail to realize is that most panels change over time, beyond just phosphor aging. I have noted for some time that the activation level on sets used on demo by my dealers change in black level and the background "activation noise" as I call it. The phenomenon is one that manufacturers don't like to discuss, but I did get a guy at Fujitsu and one at Hitachi to admit that they noted it and that changes in the panel drive and reset waveforms can moderate the effect. As I have been saying since the matter was brought up on the Panasonics, it is not just that brand. Others have said that they preprogram the sets to change drive characteristics with time to account for unspecified changes in panel behavior. Panasonic probably went a little too far in trying to keep it under control in some models.


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## Gov (Nov 21, 2007)

Thanks for the response, yes it sounds as if they went a bit to far. Truely, I have no problem with this design as long as it is not an overnight drastic change like some people are reporting. It seems as if the 58V10 and 65V10 displays have not be seeing this phenomenon, just a slight gradual rise. Just for the record, those displays were later in production and had the correct THX color from the factory. I am happy that I have the 58V10  I wonder why some of this smaller V10 displays and other 11G/12G models are more prone to the drastic change.


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## lcaillo (May 2, 2006)

I would have no problem with it at all if they document what they are actually doing and how the panels vary. The sets should be field alignable to account for such variance, not depending solely on some preprogrammed assumptions. This is akin to trying to do full calibration at the factory. It has been proven many times not to work. Some auto adjusting methods have achieved reasonable ballpark results, like the auto kine bias circuits in many CRTs, but they still require tweaking if you want to really get it right.


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## Gov (Nov 21, 2007)

Ultimate AV Mag.com Blog
http://blog.ultimateavmag.com/scottwilkinson/panasonics_black_eye/


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## Gov (Nov 21, 2007)

I have personally begun to notice a bit of an MLL rise on my 58V10. I noticed it around the 600 hour marker. My black levels are still fairly good though. If they do continue to rise, I can forsee this becoming unacceptable to me.

Some of the latest buzz on this issue.

http://blog.ultimateavmag.com/scott...r input. Your comment was posted to the site.

http://news.cnet.com/8301-17938_105-10462105-1.html?tag=mncol


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