dal forum di AVS post
#198: (SPERIAMO SIA VERO !)
"I think i might have figured out what may cause the problem in these panels, and it might be possible that Panasonic rectifies the problem with a firmwareupdate, so if you have a screen that has no marks behind the glass or you are on your third set, you might just want to hold on to it for a couple of weeks...
To understand what is happening, first a lesson in plasma display technology:
The plasma panel is filled-up with two gasses: xenon and neon and when a charge is applied, these emit ultra-violet light that by phosphors is converted to visible light.
A pixel in the screen is made up of three subpixels: R,G and B i call each subpixel a cell.
Every cell is connected with three electrodes, two on the top of the cell: T1 and T2, and one behind the cell B:.
To make a cell emit light is not as simple as putting a voltage between a couple of electrodes, but is a process of different steps, these steps may be different or more elaborate per manufacturer, but they always follow at least the following steps: (all steps combined is one cycle)
1. A charge is applied between the B and T1/T2 electrodes that causes the gas in the cell to be charged with electrons. This creates a energized plasma cloud in the cell (hence the name plasma panel). The longer the charge is applied the further the cell is charged, this determines the brightness of the cell. The cell wont emit light at this point, it is just a charge, like charging up a capacitor.
2. A high voltage is put on the T1(+) and T2(-) electrodes, this causes the energized plasmacloud to discharge and emit light.
3. Again a high voltage is put on the Top electrodes, but now in reverse voltage T1(-) and T2(+). This again creates a discharge of the remaining electrons in the plasma cloud, but it also clears or erases any left over electrons in the cell so the cell will be ready for the next cycle, just like draining a capacitor. If the cell isn't completely drained of electrons it will burn brighter the next cycle because of left over electrons. This is really an important step.
My idea of the problem in these panels is that the cells in the green blob somehow won't loose their charge completely. This may be caused by too much phosphor in the cell or other effects that may reduce discharging. I tested this theory by looking at green slides immediately when the tv is turned on. At this point the green blob on my screen was very small, and i could see traces of the sd-card menutext in the area of the green blob lighting up brighter. Furthermore i had extensive contact with Panasonic e-care, and they told me that they are working on a firmware solution to this problem that should be ready in two weeks. It is my believe that the whole green blob can dissapear when step 3 is executed better or longer or multiple times over.
Just for the record, i am not related to Panasonic, but i did develop driver circuits for Philips/Hitachi plasma panels some years ago."
tranne che se la cosa fosse vera tra un paio di settimane potrebbe essere pronto un FW risolutivo
