Spotty backlight pattern on 820-2936 after liquid damage

[spakhnyuk]

820-2936 was originally liquid damaged. There was corrosion around the LVDS connector. I cleaned the board and swapped the LVDS connector. Backlight works but it seems that not all the LEDs are working. I'm getting a spotty LED backlight pattern (see photos). It's not the display because I tried several other displays with the same exact result. Any ideas?

 

[XooP]

Had the same issue a couple of weeks ago and like Louis says it was one of the lines from the U9701. In my case it got worse when i dimmed the backlight.

 

[spakhnyuk]

Awesome! I will try this and let you guys know.

 

[1centchips]

Hi spakhnyuk, does the connector lock the cable? Check if the actual grounding/locking plate works on the board.

 

[spakhnyuk]

Yes I believe it does. I currently don't have the schematic for this board. As soon as I get the schematic I'll double check what larossmann mentioned and get back to you guys.

 

[JorgePayar]

I had the same problem in a 820 3115b till yesterday, then I checked and it was because a resistor, over that area that Duke and Louis said. Now it is working perfect!!

 

[spakhnyuk]

I'm still trying to work mine out, but I'm glad this thread helped you!

 

[spakhnyuk]

None of 6 LED_RETURN resistors are open.


When I wiggle the LVDS connector, the backlight issues seems to correct itself which leads me to a bad LVDS connector or a bad LVDS cable.
Still diagnosing.

 

[JorgePayar]

I don´t think is the cable. Not in my case at least. Could you post a picture to watch carefully the u9701 area?

 

[dukefawks]

Bad soldering on the new connector seems likely.

 

[Tony Tone]

Got that once from an LCD repair only on the left side. I thought I didn't put that sliver bar in right. Thanks, if I see it again, I know its something I have to fix.

 

[leonattpcs]

What are led returns for, do they tell the computer the led screen is on?

 

[dukefawks]

There is one line that feeds all of the leds together. There are 6 return lines that are distributed over a few the LEDS. Not really sure why there are 6 return lines, in theory it should be possible to tie them all together and just make it one. I guess it must have something to do with the design of the LED driver chip or LCD.