LG 42LH50 Turns on has backlight no picture.

[capkid]

Re: LG 42LH50 Turns on has backlight no picture.

I brought Shinju's TV home to see if I could help get it working. I connected an A/V component in an attempt to see if the TV had sound, but I got nothing when I blindly switched inputs. I noticed that the speaker voltage was only 0.4V, but the service manual says it should be 10V.

Long story short, I continued to test the main board, CAREFULLY probing the pins at IC2403 (I think this was the IC), and I saw a spark; I immediately shut off the TV. When I turned it back on, I had a picture and sound. Weird. I let the TV sit overnight unplugged, and it fired up normally when I turned it on today. Did I somehow trigger a reset?

[Shinju]

Re: LG 42LH50 Turns on has backlight no picture.

Crazy, I probed that exact IC and even got a spark and saw the panel shut off and reboot but no picture or sound.

Just wondering why the other mainboard didn't work either.

LG and their quirks!

Thanks Capkid!

[capkid]

Re: LG 42LH50 Turns on has backlight no picture.

Scooby Doo would have been proud

[Shinju]

Re: LG 42LH50 Turns on has backlight no picture.

So I wanted to update this thread.

The LG died lastnight, I saw it happen, the sound cut in and out, the picture as well, when it finally went the screen had green blocks on it and the sound was almost like a 56k modem sound.

The remote/side buttons were un responsive so I killed the power by the master switch. When I turned it back in it was back to square one again. Turns on, backlights turn on and that's it.

Mainboard is the culprit for sure, so if anyone knows a place that repairs mainboards please pipe in!

[capkid]

Re: LG 42LH50 Turns on has backlight no picture.

/bump

Open to suggestions!

Also if anyone else reads this here or via google and you have a working unit please chime in on the LED LD2400 light you can see it from the back of the panel just above the input section on the upper right side plain as day if its illuminated!

Since we both saw sparks while probing IC2403, I'd start there. Try applying freeze spray to the IC and then to the areas nearby to see what happens.

[Shinju]

Re: LG 42LH50 Turns on has backlight no picture.

Since we both saw sparks while probing IC2403, I'd start there. Try applying freeze spray to the IC and then to the areas nearby to see what happens.

Will do!

On a good note, the Sony KDL-46VL160 is still going!

[willygee]

Re: LG 42LH50 Turns on has backlight no picture.

Will do!

On a good note, the Sony KDL-46VL160 is still going!

Hi All - first time post...

Shinju I've been reading your experience with the 42LH50 and have the exact same issue. Red light before powering on, blinks, goes to solid blue but nothing - cant get to inputs or menu although the blue light will blink when i press buttons indicating that the command is acknowledged but nothing shows up on screen. Backlight is illuminated as you show in your pics as well.

Did you ever continue to mess with this or finally give up? BTW, i am a novice when it comes to tv repair but have some tools and am willing to dabble. Saw some things online whereby capacitors were the issue - havent opened my unit up to inspect as I just starting to research. I'm sure u've checked and guessing that bad capacitors would not cause this issue?

[Shinju]

Re: LG 42LH50 Turns on has backlight no picture.

Hey there!

In short I had to get a new mainboard, I don't know what the cause of death is with these but apparently it is common enough problem with the 42/47" that mainhoards are in short supply and command high dollar amounts.


Capkid and I think it might be a corrupted EEPROM issue but again that is all speculation.


The panel is still up and running with the new/use mainboard with no problems.

Sorry not much help.

[willygee]

Re: LG 42LH50 Turns on has backlight no picture.

Hey there!

In short I had to get a new mainboard, I don't know what the cause of death is with these but apparently it is common enough problem with the 42/47" that mainhoards are in short supply and command high dollar amounts.


Capkid and I think it might be a corrupted EEPROM issue but again that is all speculation.


The panel is still up and running with the new/use mainboard with no problems.

Sorry not much help.

Thanks for the reply. In my research it appears to be one of three things, 1) bad capacitor, 2) bad tcon board, 3) bad main board (the latter two you covered). On one site it basically said if you have no sound but backlight works (which I believe is my issue) than it is either t-con or main board which doesnt really help narrow it. I opened up my unit and capacitors appear intact, which I was hopeful was more the issue...

What range should I expect to pay for main and t-con board? What exactly is "high-dollar" amount?

[budm]

Re: LG 42LH50 Turns on has backlight no picture.

Shinju, that IC capkid and you pointed out is the switching power supply IC. can you read the numbers on it?
When you mention about the MODEM noise it makes, it remind me of bad caps in the SAMSUNG that makes squealing sound and cycle power on and off.

[Shinju]

Re: LG 42LH50 Turns on has backlight no picture.

Shinju, that IC capkid and you pointed out is the switching power supply IC. can you read the numbers on it?
When you mention about the MODEM noise it makes, it remind me of bad caps in the SAMSUNG that makes squealing sound and cycle power on and off.

I will dig up the old mainboard and take a peek. I also have the full service manual for this unit too.

[AFajitas]

Re: LG 42LH50 Turns on has backlight no picture.

oops

[willygee]

Re: LG 42LH50 Turns on has backlight no picture.

I will dig up the old mainboard and take a peek. I also have the full service manual for this unit too.

Shinju where did you acquire your mainboard? I've checked places online and locally and it is not easily found. your guidance would be appreciated.

[Shinju]

Re: LG 42LH50 Turns on has backlight no picture.

I am trying to find it still. I know i did not toss it.

[willygee]

Re: LG 42LH50 Turns on has backlight no picture.

I am trying to find it still. I know i did not toss it.

Sorry I meant the one you bought to get your LH50 working again (not the old broken one). Wondering where you purchased and for how much as I am not having much luck.

[Shinju]

Re: LG 42LH50 Turns on has backlight no picture.

I found it on ebay.