LG 42LB5600-UZ No Picture, Sound OK

[TheRic]

Backgroud
I have a LG 42LB5600-UZ, The screen is dark but sound works. When doing the flashlight test I can see the picture.

Ground on Chassis
Tested the voltage at the backlight connector, it hangs at 102VDC. When I first turn on the TV, the voltage at the the backlight jumps up to about 260VDC after about 1-2 seconds, then ramps down over about 5-10 seconds down to 102VDC. I get the same voltage with the LEDs connected or not connected.

Ground on LED-
Tested the voltage at the backlight connector, it hangs at 0.01VDC. When I first turn on the TV, the voltage at the the backlight jumps up to about 150VDC after about 1-2 seconds, then ramps down over about 5-10 seconds down to 0.01VDC. I get the same voltage with the LEDs connected or not connected.


Questions:
Is this normal voltage? I've read where it's supposed to be a higher.
I'm assuming it's bad backlight. I figured I would just replace the LED's, read it's a heck of a lot cheaper. How/where do I find out what LED's I need? Is there a standard?

Thanks for your help, If you need more info just let me know.

[R_J]

Re: LG 42LB5600-UZ No Picture, Sound OK

The power supply supplies a base 102vdc for the led circuit, the led BOOST circuit will boost that voltage to light the led's, to around 208vdc, the fact that it is around 260VDC indicates an OPEN led string in the panel.
It won't be cheaper if you crack the panel so be carefull with it and remember the diffuser sheet sequence so they go back the same way.
Lokks like shopjimmy carries the led strips for this model

[neilc6]

Re: LG 42LB5600-UZ No Picture, Sound OK

These are likely your strips though you should open up the panel to confirm the part number printed on them. https://ebay.us/xnlym6

[TheRic]

Re: LG 42LB5600-UZ No Picture, Sound OK

Thanks for your help.

To clarify was talking of replacing individual LED's verses the strip.

I have Part Number/Model Number for the Backlights / backboard assembly as T420HVF07.1

[R_J]

Re: LG 42LB5600-UZ No Picture, Sound OK

Which ever way you go, make sure to check the led operation, BEFORE reinstalling the lcd panel. The tv will turn on and light the led's without the panel connected.
If you just replace one or two led's having them lit will help in realigning the lens

[neilc6]

Re: LG 42LB5600-UZ No Picture, Sound OK

I would recommend just replacing all the strips. The working LEDs have wear and are likely to fail in the future. The tape for the strips is super sticky and you are likely to pop off the lenses removing the strip. The lenses if they aren't lined up exactly will cause halos when reglued.