Originally Posted by Bdemers
To the many people recently joining the discussion....
The root cause of the issue has been well-discussed earlier in this thread. Search for the word "patent" and I suspect you'll find it.
Here's the basic-basic explanation, apologies if this over-simplifies the situation for some people's tastes:
The plasma cells continuously undergo a repeated cycle in order to control their intensity. First step: they are initialized. A small voltage activates the cells and prepares them for the next step. Then, step two: they are addressed. This step determines which cells will be illuminated in the third step. Third step, they are sustained. Voltage is applied to the panel to keep the addressed cells bright for the cycle. The the sustain ends, and we return to step 1 to prep the cells for the next addressing. This happens at 480 Hz on the 12G panels, and 600Hz for THX mode. (higher frequency increases color accuracy)
The issue we're discussing deals with the initialization voltage. The lower the voltage, the darker the black level of the panel. The problem is.... if the voltage is too low, and cells don't get initialized, they can't be addressed, and then can't be sustained. (they will not light up when asked to)
So... if the voltage drops below a certain threshold, the cells will misfire. This is a bad, bad situation.
So, it's easy: make sure the initialization voltage isn't too high, or too low.
Where the issue gets tricky is that that threshold is a moving target. As the plasma cells age, the voltage required for initialization increases. If the panel anticipates and matches this need properly, the black levels should not experience much rise. The point is to just tip the cells over their initialization threshold, no further.
With the Panasonic panels, it appears that the initialization voltage driver over-compensates for the rise and increases the MLL of the panel.
Basically, using bogus numbers:
Perhaps cells wanted 12V to be initialized when the panel was new. After 500 hours, now it's more like 13.5V. If you hit that 13.5 dead-on, they'll be primed, without negative effects on black level. If you hit them with 14V, you'll increase the black level for no good reason. That's basically what's happening here.
From what we've been able to learn, it sounds like the panel won't "catch up" with the voltage over time, because (based on Panny's patent information), eventually the necessity for voltage increases ends. The cells do not experience much further wear. (the voltage climb flatlines) Based on the patent, this may happen around 1000 hours, but it certainly depends on the specific panel design.
If at this point (1000 hours?) the initialization voltage is too high, it will likely ALWAYS be too high, even if it stops increasing.
Hope that clarifies the situation for some of the newcomers. If I've made any mistakes/errors/omissions, please feel free to correct/comment.