Samsung UE46C6530 Bright patches on screen

[DemonBG]

Hi all,

Im currently working on this Samsung 46" LED tv which has two bright patches on either side of the screen (roughly where the speakers are mounted under the frame).

Originally this TV had a faulty main board (which i have now replaced) but this particular symptom remains between the old and new main boards.


Any suggestions on what to check please?


Thank you,
Demon

[tom66]

Re: Samsung UE46C6530 Bright patches on screen

My first guess would be something related to the LEDs on the bottom of the panel. Have they perhaps moved out of alignment while you were working on the set, or perhaps the diffuser film near them has? Alternatively, it is possible that those LEDs are stuck on 100% bright for some reason (whereas the others are on something like, say, 50% brightness.)

[tibimakai]

Re: Samsung UE46C6530 Bright patches on screen

..or maybe the middle ones are off.

[stj]

Re: Samsung UE46C6530 Bright patches on screen

2 very distinct points,

maybe it's a group of 3 in series and the center one is shorted.

[DemonBG]

Re: Samsung UE46C6530 Bright patches on screen

Thanks for the replies all.

Could this be a T-con issue? The reason i ask is that today i unplugged the LVDS cable and the backlight alone came on and the screen was fairly uniformly lit...

I then connected only 1 side at a time on the T-con to test each half of the screen and had the same result - the side with the image had a bright patch (red circle) and the side without an image was uniformly lit. (pictures attached)


I noticed that on darker images as well that the contrast gradient was very poor - The transition between colors was very "blocky" (see pic for example... it is not as smooth as i would expect). would this suggest it is a T-con problem? Is there any way to test?



Thanks again all,
Demon


Thanks all,
Demon

[tom66]

Re: Samsung UE46C6530 Bright patches on screen

That's very odd, I have never seen a bad LCD panel do that (overbright in corners) so I don't know why it disappears with the ribbons out. Would you say the effect is completely gone? The image being solarised with one ribbon out isn't entirely unusual.

[DemonBG]

Re: Samsung UE46C6530 Bright patches on screen

Hi Tom,

Yes on the side with the ribbon cable out the backlight is completely normal and on the side with the ribbon cable in it is still overbright.

I am thinking this may have something to do with the fact that it is an LED tv and i read somewhere that they are able to dynamically adjust the brightness in different areas based on the image.... which would explain why the T-Con may also control an element of the LED circuitry?


Take care all,
Demon

[DemonBG]

Re: Samsung UE46C6530 Bright patches on screen

Just found this with reference to LED blocks on LG LED tv's which may explain it:

"An individual block is manipulated by the T-CON board. These blocks are manipulated Global (All at once) and in accordance with the video intensity at the specific location of the block of LEDs for that video content (Local). In other words, if the video is dark in the area of the screen"

Source: http://electro-medical.blogspot.co.u...backlight.html

What do you think?

Thanks,
Demon

[tom66]

Re: Samsung UE46C6530 Bright patches on screen

Some LED TVs called "Full LED TV" can dim individual parts of the image, but AFAIK that is not used any more on Samsung TVs. Sometimes they can dim the edges of the image though. Can you supply a picture of your T-con board? Any LED backlight control is usually on a separate PCB and will not be through the T-con panel ribbon but through the main board and PSU (usually) or sometimes T-con to PSU.

[DemonBG]

Re: Samsung UE46C6530 Bright patches on screen

Correct you are sir! I just did a bit more reading and it seems that although on the LG tv's this is done through the T-con there are wires going directly to the LED drivers.

Pictures attached all the same.

Also - Just to confim, with 1 ribbon cable unplugged, the half of the screen with the image does still have the overbright section (the picture i posted before does not show it well...)

[tibimakai]

Re: Samsung UE46C6530 Bright patches on screen

I would take the panel apart and see what is going on.

[DemonBG]

Re: Samsung UE46C6530 Bright patches on screen

Thanks for the replies all.

Tibimakai - because of the issue with the funny colors and whatnot i am leaning toward thinking this is a T-con issue... (or both?) I have another of these TV's at my brothers place so over the coming weeks i will take the full set of boards over to his place and see if i get the same results...

I will post back when i have an update.

In the meantime - Is there any way i can probe / test the T-con board?

Thanks,
Demon

[DemonBG]

Re: Samsung UE46C6530 Bright patches on screen

Update-Fixed!

Hi all,

Ok so as i had guessed, this one turned out to be a faulty T-con board...

I must admit, i had no idea a faulty T-Con could result in the bright patches, but what game me the idea was the funny colors on the screen!


Either way, i hope this solution helps someone else out there as well!

All the best,
Demon