LG 55UK6950PLB backlight but no picture

[notallbad]

On power up the backlight comes on but no picture
Power on - 3.4v
13.2v - 13.2v
Drv_on - 3.25v
V-Sync - 0.04v
SIN - 0.02v
SClk - 0.01v
P-dim - 1.4v
P-dim2 - 1.3v

With the left tcon ribbon removed just backlight still on fulscreen, no change.
With the right tcon ribbon removed that half of the screen is considerably darker.

Any advise please.
thanks

[notallbad]

Re: LG 55UK6950PLB backlight but no picture

in stby the 13.2v line is jumping around between 8.2v and 8.6v

Also dont seem to be able to get any sound.

[chopdre]

Re: LG 55UK6950PLB backlight but no picture

seems like a panel issue, you need to block the ckv lines on the faulty side of screen

[William1967]

Re: LG 55UK6950PLB backlight but no picture

The panel has a problem, it's a common fault with these models and several other models from LG. The AVDD must be around 17v and is only present on one side when you disconnect one of the LVDS cables.

[notallbad]

Re: LG 55UK6950PLB backlight but no picture

thanks william
shall check that out
is it a fault within the actual panel or the boards attached to the panel? fixable or just scrap?
thanks

[notallbad]

Re: LG 55UK6950PLB backlight but no picture

Both ribbon cables connected theres no volts on AVDD, left or right.
With the right ribbon cable disconnected the AVDD on the left is 17v.
With the left ribbon cable disconnected theres 0v on AVDD on the right.

There is 17v on both ribbon cables when disconnected.

[William1967]

Re: LG 55UK6950PLB backlight but no picture

I have 4 over here with the same problem, I only had a little time to investigate where it comes from and until now I have to say it's inside the panel...

[notallbad]

Re: LG 55UK6950PLB backlight but no picture

ok may as well strip it down and trash the screen then.
Anything you want me to check or do before its scrapped? Might help with your investigations later.

[William1967]

Re: LG 55UK6950PLB backlight but no picture

I've gone a little further with one of the displays and by cutting some lines there was picture, unfortunately there were black flashing lines on the left side of the display.
On the second display I could not get any picture at all. I'm not going to open both other tv's, they will go back to the owners. In one word said these tv's are garbage!

[dskall]

Re: LG 55UK6950PLB backlight but no picture

You can run down the short if you are interested. Maybe able to bypass shorted area and go directly to COF with wire.

[Davi.p]

Re: LG 55UK6950PLB backlight but no picture

The fault may be within the display distribution boards, maybe a shorted cap, needs slow current supplying on avdd line especially, to be safe 1,8/3,3v supply lines must be present.

[notallbad]

Re: LG 55UK6950PLB backlight but no picture

Found the fault! Burnt out on one of the tab bonds.

Not a very good photo, sorry but you get the idea.

So this ones toast! Shall strip down for parts.
Thanks for the help! Appreciate it!!!

[dskall]

Re: LG 55UK6950PLB backlight but no picture

Thanks for follow up.

[Monty74]

Re: LG 55UK6950PLB backlight but no picture

Found the fault! Burnt out on one of the tab bonds.

Not a very good photo, sorry but you get the idea.

So this ones toast! Shall strip down for parts.
Thanks for the help! Appreciate it!!!

Hi notallbad, did you have to trash the screen to get to the burnt out tab bond? I have one of these screens and wanted to attempt a repair as I too have backlight but no picture. Is this a ribbon cable of some kind that has burnt out? I cant really see as the picture is not so clear as mentioned. I just want to know if its repairable on a micro soldering scale? Regards Craig

[nomoresonys]

Re: LG 55UK6950PLB backlight but no picture

simple things first, try unplugging wifi and speakers, turn tv on see if there's any change.

[viewerau]

Re: LG 55UK6950PLB backlight but no picture

seems like a panel issue, you need to block the ckv lines on the faulty side of screen

How is this process done please?

[nomoresonys]

Re: LG 55UK6950PLB backlight but no picture

tape cutoff method, video there and many more, youtube: https://www.youtube.com/watch?v=pfrRhw7-ZII

[viewerau]

Re: LG 55UK6950PLB backlight but no picture

tape cutoff method, video there and many more, youtube: https://www.youtube.com/watch?v=pfrRhw7-ZII

Thank you...

This is my t-con

I see CLK 1-8 on the top right of my t-con, but unlike his board, which shows the lines going to the ribbon area, in mine, I see no lines like his were.

So how do I know which one's to tape?

Thank you.

[lotas]

Re: LG 55UK6950PLB backlight but no picture

thank you...

This is my t-con

i see clk 1-8 on the top right of my t-con, but unlike his board, which shows the lines going to the ribbon area, in mine, i see no lines like his were.

So how do i know which one's to tape?

Thank you.

ckv

[viewerau]

Re: LG 55UK6950PLB backlight but no picture

Hi lotas.

I am sorry, I do not understand your reply...my apology.