Lg 47lb582v blinking backlight

[w3svc]

I have a LG 47LB582V where the backlight blinks. Have checked and replaced all bad LED's byt it still blinks.

I've messed arround the power supply and suspect it is faulty: see attached pic below.

Any suggestions arround where the fault might be?

[R_J]

Re: Lg 47lb582v blinking backlight

I would put my money on faulty led's in the panel. If you want to be sure you would need to swap the two led strings around, or you could try swaping complete strips that are connected on the one string with the other and see how it effects the power supply voltage (does the lower voltage switch to the other pair of leds)
You do not need to install the lcd panel to have the leds turn on and see which are lit up or flickering

[w3svc]

Re: Lg 47lb582v blinking backlight

The result is the same reguardless on how I connect the led-strips. Tried that aswell.. Perhaps should have mentioned that

[w3svc]

Re: Lg 47lb582v blinking backlight

I would put my money on faulty led's in the panel. If you want to be sure you would need to swap the two led strings around, or you could try swaping complete strips that are connected on the one string with the other and see how it effects the power supply voltage (does the lower voltage switch to the other pair of leds)
You do not need to install the lcd panel to have the leds turn on and see which are lit up or flickering

The result is the same reguardless on how I connect the led-strips. Tried that aswell.. Perhaps should have mentioned that

[budm]

Re: Lg 47lb582v blinking backlight

Can we see the straight pictures of the whole top and bottom side of the power supply board?
What is the P/N of the board?

[w3svc]

Re: Lg 47lb582v blinking backlight

can we see the straight pictures of the whole top and bottom side of the power supply board?
What is the p/n of the board?

p/n: 3pcr00367b

[budm]

Re: Lg 47lb582v blinking backlight

p/n: 3pcr00367b

That is not the P/N of the board:
Your pictures is not clear enough for me to read much of anything.
The PCB P/N is EAX????????
The PCBA P/N is printed on the barcode sticker.

[petehall347]

Re: Lg 47lb582v blinking backlight

65423801 (2) .1)... for eax
barcode scanner cannot pick up the barcode

[w3svc]

Re: Lg 47lb582v blinking backlight

that is not the p/n of the board:
Your pictures is not clear enough for me to read much of anything.
The pcb p/n is eax????????
The pcba p/n is printed on the barcode sticker.

pcb: Eax65423801 (2.1) rev 2.2

[w3svc]

Re: Lg 47lb582v blinking backlight

65423801 (2) .1)... for eax
barcode scanner cannot pick up the barcode

See if this helps more.

[Trofazni]

Re: Lg 47lb582v blinking backlight

Hi to all!
I will jump into this thread, because I have the same problem, on the same power supply.
Anyway, leds are ok, one string replaced with new, second repaired, tested, and ok.
When it flickers, only the old, repaired set of leds is blinking, new installed does not. So, one of two power supplies for leds is faulty on pwboard. Checked caps, diodes, resistors, checked for shorts, everything seems ok, so I guess I am missing something.
In my opinion when leds died they draw too much current or made shorts and burned something in power supply in led pwm sector. I did some measuring on one diode i have odd voltage pulsing 3-4V, although voltage drop across diode should be 0,4V, Replaced it even it was measurin ok on multimeter voltage drop test, 0,4V, replaced it still, but everything stays the same.
On video you can see voltage on that diode, and two that go to led strips...
If anyone has idea or service manual, that would be great.. I bought new led, not knowing it has power supply problem.. Thanks

https://www.youtube.com/watch?v=4pei...ature=youtu.be

[R_J]

Re: Lg 47lb582v blinking backlight

exchange both the + &- wires of the two led strings, that will tell you if it is the repaired string is at fault or the power supply. If the new string is working and the repaired string is flickering, I would suspect a weak/intermitint led in the repaired string.

[Trofazni]

Re: Lg 47lb582v blinking backlight

I will try that, although every single led in repaired strip is tester separetly, from begining to the end, even every one*s resistance to the chasis.. all measuring as should.
I will replace power lines of strings and write tomorrow when I get to work..

[budm]

Re: Lg 47lb582v blinking backlight

What is the spec of the replacement LED's?
Did you test as the whole string? I know you test individual LED.
BTW, is your TV the same model and same screen size?
If you look at the LED Voltage you will see that different screen size the two LED strings may not have the same Voltage due to the two LED strings may not be the same.
So be careful when swapping the LED wires.

[dick_barton]

Re: Lg 47lb582v blinking backlight

The working led voltage as seen in the picture (bit blurred) in post #6 looks as though it should be 117V for each string. What are you measuring?

[Trofazni]

Re: Lg 47lb582v blinking backlight

Ok, I solved it.. First I tried to swap power lines of 2 strings, came out the same situation.. So, I guessed that NEW strings are not working. Soldered 10 leds on a test board to imitate string and it worked. One of two new strings was bad. As i tested it, found out that one of 4 half strings (two A and two B), is making problems. When I isolated problem to only one half of string, I tested each diode, and they worked??? Checked for shorts to ground and else, all ok.. Finally I removed test leds, and suddenly everything is working without any changes. So, I am guessing that one solder point where connector is soldered was bad, when i soldered test leds, probably repaired contact not knowing it was problem.. I have no other explanation on this problem, taking that I did not change anything but soldering wires on connector points...
Thank for ideas, they really helped, I would not suspect faulty contacts on new strings that have been tested fine, one by one, even 3 in a series tested fine.. Did not have such an experience...

[Skeltek]

Re: Lg 47lb582v blinking backlight

https://www.youtube.com/watch?v=4pei...ature=youtu.be

I got the same issue like in your video (my sisters TV broke down, the board is a PBC: EAX65423801 (2.2) REV 2.1 and the TV is an LG 55 something). The Backlight periodically turns up, then goes black again in 1 second intervalls, while sound and all other functionality seems fine.
Looking closely, I saw 1 bright flash on all sides of the monitor (one can see the backlight shine through the sides, once the back panel of the TV casing is removed), followed by 2 dimm flashes. All seem to pulse periodically bright-dimm-dimm-repeat with a 1 second period.
I unplugged the backlight power connector on the power supply and measured the voltage there. Without the backlight plugged in my multimeter shows 0V-4 2V-0V-8V-repeat. Maybe the voltage is higher, but the multimeter needs a fraction of a second to measure.
Since I do not know how the PSU board reacts without the backligth plugged in, I could only presume it was a defect in the PSU board, since the voltage keeps pulsing even without the backlight being attached.
Why does the voltage keep pulsing, even without the backlight being attached? Is the board defective as follow-up damage, or is it normal behavior of the PSU board, when something is wrong with the backlight? As I understood, a repair of the PSU board was not required in Trofaznis case.

I did not quiet understand above descriptions though, since I am unsure what the difference is between a strip and a string in that context.
Since I presume Trofazni is german (his TV shows german text) or croatian (like his profile indicates), maybe he could message me in private (I speak both languages among others) before I post my solution here.

[nomoresonys]

Re: Lg 47lb582v blinking backlight

could be a connection problem like this for example: https://www.youtube.com/watch?v=cfHPKs4UFfc

[Skeltek]

Re: Lg 47lb582v blinking backlight

could be a connection problem like this for example: https://www.youtube.com/watch?v=cfHPKs4UFfc

Well, I got several broken LEDs, but most apparently all the stripes seem to be receiving power. Can LEDs short-circuit?
I made a video and this is a screenshot of just during the LEDs flaring up.
As one can see, almost every strip has at least one defective LED.
I am going to order new LED strips, but I am unsure which one to order at which store.
A search gives me all kinds of results, but none for an LG 55LF5809

Also what remains is just the hope this would fix it. I would still probably have to wait until beginning of November to get them delivered.
I also made an analysis on the psu board, but like I earlier said I am unsure how the board is supposed to behave when the backlight is not plugged in. It also seems to pulce the voltage, but that could be from there being no consumer and it shuts down then?

[alfatv]

Re: Lg 47lb582v blinking backlight

LED short circuit is typical.
Any LB or LF strips should fit as long as screen size is the same.
Light uniformity will never be as good as original.