TV Led lg 32ln575 - no backlight

[Ad-M]

TV is LG LED 32ln575
Power supply: EAX64905001(2.6)

There is sound, everything is working, just no backlight.

Led+ give no voltage (1v or less)(doesn't matter if connected or not). I just have no idea why. I tried many things for last few days... Today I changed power supply to EAX64905001(2.4) (from different TV) and still no backlight (no voltage on LED+ connector).

I measured voltage for Connectors to the Mother Board: (stand by)
0(GND) 0(GND)
0 (12v) 0 (n.c.)
0 (12v) 0 (12v)
0 (GND) 0 (GND)
0 (24v) 0 (24v)
0 (GND) 0 (GND)
3.37v (3.5v) 0 (n.c.)
3.37v (3.5v) 0 (PDIM)
0 (PWR-ON) 0 (DRV-ON)

(Power ON)
0(GND) 0 (GND)
12v (12v) 23,7v (n.c.)
12v (12v) 12v (12v)
0 (GND) 0 (GND)
23.7 (24v) 23,7v (24v)
0 (GND) 0 (GND)
3.43v (3.5v) 0 (n.c.)
3.43v (3.5v) 1,1v (PDIM)
3.29v (PWR-ON) 3.0v (DRV-ON)

Nothing seems off to me.

I would be grateful for any advice.

[budm]

Re: TV Led lg 32ln575 - no backlight

So the replacement power supply board is a known good working board for sure?
You do have all the correct controls signals from the main board.

[dick_barton]

Re: TV Led lg 32ln575 - no backlight

Suspect an led problem. Shine a very bright light on the screen and look very carefully to see if you can make the picture out. Select menu on remote.

[budm]

Re: TV Led lg 32ln575 - no backlight

You may want to read this thread:
https://www.badcaps.net/forum/showthread.php?p=650876

[CapLeaker]

Re: TV Led lg 32ln575 - no backlight

It's not an LED problem. I rather think there is a problem with the driver on that board.

budm beat me to it.

[dick_barton]

Re: TV Led lg 32ln575 - no backlight

I just followed Budm's link and it looks to be an identical problem with the driver chip.
I think the hint I should have picked up on was no LED voltage whether plugged in or not.

[budm]

Re: TV Led lg 32ln575 - no backlight

Yes, it is the same board, the PCBA P/N is LG EAY62810301, the EAX???? is the blank PCB #.
Always match the board with the PCBA number since blank PCB can be stuffed in many ways to make many PCBAs for many models of TVs.

[Ad-M]

Re: TV Led lg 32ln575 - no backlight

@Yes, there is picture if i use flashlight.
@I read this thread earlier, on VCC i have 12v.
If I disconnection LEDs, then shouldn't there be some voltage if LEDs are broken?
@I cant be 100% sure about this second power supply, is from TV with broken screen and for now I can't check it in any other way than connecting to this TV.
This is PCBA number?: LGIT PCB P/N:3PCR00274B

edit: i added .pdf file. On page 19 is power supply schematic.

[Dcole73]

Re: TV Led lg 32ln575 - no backlight

Hello Ad-M.

Were you able to resolve this issue?

Here's some info that may help.

I think one or two of the LEDs in your tv are bad.
Since they are connected in series, if one is bad, others won't work. You have to open it up and test each LED to find the faulty one.
The bad LED needs to be replaced. It is usually easier to replace the strip containing the bad LEDs .

NOTE: The voltage for the back lights is 195V DC. So ensure it is disconnected from the power board before working on the LEDs.