Samsung UE46B7020WW screen issue.

[Dang]

Hi again, managed to get a hold of this quite cheaply so was worth a punt, as you can see from the photos it's suffering a type of picture distortion, there's horizontal lines, looks like a pixel width missing every few milimetres, there's also a vertical discolouration passing through anything displayed, there's one last thing I've noticed and that is a "whitening" to the screen the higher the brightness is turned up, I'm not too sure what the issue is but I'm hoping not the screen, if anyone can shed some light on what it could be I'd be very grateful, thanks, Andy.

[tom66]

Re: Samsung UE46B7020WW screen issue.

Probably a bad panel.
I got a 40" A656 with a similar fault, haven't had a good look at it yet, but suspect the panel to be bad.

[Dang]

Re: Samsung UE46B7020WW screen issue.

Hi again Tom66, when you say bad panel, what on the panel do you think could be causing this? fixable maybe?

[tom66]

Re: Samsung UE46B7020WW screen issue.

My theory is UV/heat damage to pixels on the panel from age.

As the pixels "age" they become leaky, hence requiring a different VGL voltage to stay switched off on row-address cycle of the LCD update. (Basically the pixel TFT sees the source voltage (0-15V) plus VGL when off, if this voltage is too high, i.e. when the source voltage is high and VGL is low, the pixels will bleed into each other.) Note VGL is negative, about -5V to -8V.

Ideas for fix:
- find a way to increase VGL a few volts
- find a way to decrease AVDD (will decrease picture brightness)

I might be completely wrong on this though - your fault is slightly different as my set does not have the horizontal lines. On mine, if contrast is below about 70, the effect disappears entirely (except on the menus which are fixed brightness) and the TV is quite watchable.

[Dang]

Re: Samsung UE46B7020WW screen issue.

Well, I've found this video http://www.youtube.com/watch?v=7znmARyz16k, same size screen with the exact same error so you could be right Tom66.