big shadow on LCD screen

[paulstef]

Hi , I'm a bit lost here.

This is a Viewsonic LCD TV 37" N3752W. I replaced all caps on the power supply secondary, they were all bad.

Now the TV is running but has like a big shadow on the left side. It is much more visible when the picture is darker (but not black). So for the second picture I turned down brightness to zero. Is this a panel/backlight problem? I can't think that this would be caused by something else (PCB )

Thanks for reading

[freakaftr8]

Re: big shadow on LCD screen

I would be inclined to say either it's a panel problem or there is something going on underneath it. Like dirt. Pull the lvds from the tcon and power up. Does the back light look even or is that dark spot still there?

[budm]

Re: big shadow on LCD screen

I have this same thing on my SAMSUNG 32", took the panel apart, removed and clean all the diffusers, polarizers, etc, without any affect. I think the only thing left is the problem on the LCD glass panel itself.

[paulstef]

Re: big shadow on LCD screen

I would be inclined to say either it's a panel problem or there is something going on underneath it. Like dirt. Pull the lvds from the tcon and power up. Does the back light look even or is that dark spot still there?

Ok, I'm gonna check this.

[paulstef]

Re: big shadow on LCD screen

I have this same thing on my SAMSUNG 32", took the panel apart, removed and clean all the diffusers, polarizers, etc, without any affect. I think the only thing left is the problem on the LCD glass panel itself.

I don't really feel like taking the panel apart. Since I never did it I think it would be worse afterwards.

I can still use it as a computer monitor or put it aside as a replacement when my main TV dies.

[budm]

Re: big shadow on LCD screen

What I try to say is that cleaning the panel did not correct the problem in my case, I had to replace my panel.

[multimeter]

Re: big shadow on LCD screen

i think this is a "mura"problem,caused by either bad lcd,bad diffuser sheets.

normally this problem is terminal and will get worse.

fix: replace panel if cheap enough.

[paulstef]

Re: big shadow on LCD screen

Thanks guys,

this is bad news. The TV is seven years old, ANY price for a new panel will be too high. You can get 37" TVs for $350.

Where are the good old times when repairing something was actually worth it ? The times where a simple new TV cost $2000. :-)

[SeanB]

Re: big shadow on LCD screen

It could have been in a room where dirct sunlight hit that part of the screen during the day, which can do that with time. Best bet is keep it, and look out for a broken one of the same model to use as a screen donor. A totally non working one with a dead power supply would probably be best and should be cheap.

[paulstef]

Re: big shadow on LCD screen

Is anywhere described what EXACTLY is causing this?

Also, Budm, do you have a good reference somewhere on how exactly take apart an LCD panel. What to do and what not? In the end you replaced the whole panel and all was good?

thanks

[tvtanner]

Re: big shadow on LCD screen

Had trouble with sanyo tv with similar trouble and it was ribbon cable that feeds info to the glass panel. I pressed down on cable with hand and it went away so I taped a piece of sponge rubber across ribbon to repair. You have to remove band from around glass panel in order to do this. Check this site on sanyo troubles and you will see similar trouble. Good luck.

[paulstef]

Re: big shadow on LCD screen

Will check. Thanks.

[Alastair E]

Re: big shadow on LCD screen

Had this just recently, a Toshiba 37" set. I had repaired it and put it up for sale. The picture was fine--no sign of this effect.

By the end of the day,--There it was, a dark shapeless splodge just off centre of the screen.

The next day when the set and W/S, Shop was cold--No mura...

That afternoon--back it came....

The shop W/S is made in a steel shipping-container, thats very cold in the morning but is orientated in such a way that if its sunny--you cant keep your hand on the wall!

How depressing--Sold it off very cheap!

[paulstef]

Re: big shadow on LCD screen

Had this just recently, a Toshiba 37" set. I had repaired it and put it up for sale. The picture was fine--no sign of this effect.

By the end of the day,--There it was, a dark shapeless splodge just off centre of the screen.

The next day when the set and W/S, Shop was cold--No mura...

That afternoon--back it came....

The shop W/S is made in a steel shipping-container, thats very cold in the morning but is orientated in such a way that if its sunny--you cant keep your hand on the wall!

How depressing--Sold it off very cheap!

Mine gets a little better when it's turned on and heats up after a while.

[freakaftr8]

Re: big shadow on LCD screen

Possible diffusers are warping under heat. Only other way to tell is disconnect tcon and see if the dark spot is still there or.take it apart and use an external light to shine thru the panel and see if its there. If it is panel is bad