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-   -   Lg 32lb5700 no power on led (https://www.badcaps.net/forum/showthread.php?t=84835)

axon18 05-27-2020 04:09 AM

Lg 32lb5700 no power on led
 
6 Attachment(s)
Good Morning,
I have a TV that suddenly stopped showing pictures. After searching in the internet, i find that could be the LED tapes. I opened the TV and it really had a burnt and scorched tape led ... i replaces them all.
When I connected everything is the same.
Can you help me?

I attach the photos and measurements on and off.

Sorry my bad english.

dick_barton 05-27-2020 04:43 AM

Re: Lg 32lb5700 no power on led
 
You are missing a signal from the mainboard to turn the leds on. DRV_On should be approximately 3.5V
Disconnect the mainboard from the power supply and connect a 1K resistor from 3.5V to PWR_On and a second 1K resistor from 3.5V to DRV_ON

salarsat 05-27-2020 08:15 AM

Re: Lg 32lb5700 no power on led
 
Hello
your board need to be reball CPU !!!!
do not tuch any thing !!!

nomoresonys 05-27-2020 09:14 AM

Re: Lg 32lb5700 no power on led
 
Quote:

Originally Posted by salarsat (Post 964264)
Hello
your board need to be reball CPU !!!!
do not tuch any thing !!!

That's just a HUGE assumption.

axon18 05-28-2020 03:52 PM

Re: Lg 32lb5700 no power on led
 
Quote:

Originally Posted by dick_barton (Post 964228)
You are missing a signal from the mainboard to turn the leds on. DRV_On should be approximately 3.5V
Disconnect the mainboard from the power supply and connect a 1K resistor from 3.5V to PWR_On and a second 1K resistor from 3.5V to DRV_ON

Hello, i make what you said and the led poweer on, then i disconnectt the led and check 142vdc in led connector.

dick_barton 05-29-2020 01:56 AM

Re: Lg 32lb5700 no power on led
 
So the backlight works when you tested using the resistors, yes?

axon18 05-29-2020 02:00 AM

Re: Lg 32lb5700 no power on led
 
Yes

dick_barton 05-29-2020 02:29 AM

Re: Lg 32lb5700 no power on led
 
It looks like you have a mainboard problem not providing the signal and your leds are OK.

Can you follow the DRV_ON pin on the mainboard and see if it connects to a transistor/mosfet.

yokoono 05-29-2020 02:47 AM

Re: Lg 32lb5700 no power on led
 
Or reflow to the processor.

axon18 05-29-2020 04:53 AM

Re: Lg 32lb5700 no power on led
 
1 Attachment(s)
Quote:

Originally Posted by dick_barton (Post 964700)
It looks like you have a mainboard problem not providing the signal and your leds are OK.

Can you follow the DRV_ON pin on the mainboard and see if it connects to a transistor/mosfet.

After search i find that c701 is missing, there is olny the place with solder.
I attatch picure with the pin DRV_ON and the component that is missing.
And i don't know what is...i search the board but i can't find the manual..eax65610905

dick_barton 05-29-2020 05:17 AM

Re: Lg 32lb5700 no power on led
 
1 Attachment(s)
Why would the smd capacitor C701 be missing? It does look as though it is. Was this TV working for you or do you have it for repair? Has the mainboard been replaced or worked on?

axon18 05-29-2020 05:36 AM

Re: Lg 32lb5700 no power on led
 
The television was working. It was on a living room sideboard and then I posted it on the wall. after that it worked a few hours.
It wasn't to fix. It won't pay off. Appliances are very expensive to repair here.
Can you tell me what componet i have tu buy tu put there.. to see if works.
Regards

dick_barton 05-29-2020 05:42 AM

Re: Lg 32lb5700 no power on led
 
Unfortunately, I do not know what the component is.
Perhaps someone with an identical board could tell you but there would be no guarantee that that is the only problem. There also appears to be an smd resistor alongside that is not in circuit so it may be that they were never included in this version of the mainboard.

nomoresonys 05-29-2020 05:55 AM

Re: Lg 32lb5700 no power on led
 
That's where a MLLC capacitor would go, see all the others, look around tho, maybe this setup did not require that cap, there are many more places on that board that don't have those caps in place, see them, just because there's a place for one does not mean it was needed in this particular setup/configuration.

diif 05-29-2020 07:35 AM

Re: Lg 32lb5700 no power on led
 
Quote:

Originally Posted by axon18 (Post 964729)
After search i find that c701 is missing, there is olny the place with solder.
I attatch picure with the pin DRV_ON and the component that is missing.
And i don't know what is...i search the board but i can't find the manual..eax65610905

That's definitely looks broken off, non filled pads have more rounded solder domes. I have an identical board here and have just pulled that capacitor, it's 10uf.

dick_barton 05-29-2020 07:45 AM

Re: Lg 32lb5700 no power on led
 
1 Attachment(s)
Quote:

Originally Posted by diif (Post 964764)
That's definitely looks broken off, non filled pads have more rounded solder domes. I have an identical board here and have just pulled that capacitor, it's 10uf.

There's also an smd resistor in the photo I posted that I could not see on his original photo. Is it on your board and can you see its value.

diif 05-29-2020 08:42 AM

Re: Lg 32lb5700 no power on led
 
It's tiny and black which is why it doesn't look like it's there. It's in circuit with the two black devices either side of it, it sits lower than them so it's very unlikely it could be knocked off, unlike that cap.

nomoresonys 05-29-2020 12:29 PM

Re: Lg 32lb5700 no power on led
 
Yep, looks like it fell off or was removed, what's the tv history? another pic. there: https://www.ebay.com/itm/LG-32LB570V...-/273575219348

axon18 06-02-2020 04:44 PM

Re: Lg 32lb5700 no power on led
 
Good evening,
Thank you all for your help. I ended up buying a new card.

nomoresonys 06-02-2020 06:38 PM

Re: Lg 32lb5700 no power on led
 
Ok, let us know if it works.


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