LG47LA621Y LED TV screen flashes once

[buchman]

Hi,

My screen is flashing for a second with LG logo and then nothing. tested with flash light on the screen and I do see the menu when I press on it.
All voltages on the P201 connector are OK (which goes to the main board).
Photos attached with the voltages on the P801 connector (top left on the power supply board.
Is that a LED issue (and I have seen many of them on youtube) or it's the power supply?

[buchman]

Re: LG47LA621Y LED TV screen flashes onse

And of course the back of the PSU

[nomoresonys]

Re: LG47LA621Y LED TV screen flashes onse

Do you have all the expected voltages on power supply?

[nomoresonys]

Re: LG47LA621Y LED TV screen flashes onse

Heres a thought, someone jump in if I'm way off, havent had any lgs to play with but if you could see the service menu maybe in a darker room with a flashlight and could do a factory reset, wonder if that would do anything to fix it?

[diif]

Re: LG47LA621Y LED TV screen flashes onse

Were those voltages measured as it powered on and the logo shows or afterwards. What about with the LEDs unplugged ?

@nomoresonys, rather than guessing without a clue, perhaps do plenty more reading.

[buchman]

Re: LG47LA621Y LED TV screen flashes once

Were those voltages measured as it powered on and the logo shows or afterwards. What about with the LEDs unplugged ?

@nomoresonys, rather than guessing without a clue, perhaps do plenty more reading.

On the p201 connector 3.5V is constant. Other voltages appearing when the set is on.
When the leds P801 connector unplugged (top left) then I am getting 170V in the LED+ and then it's descending to 78V.
On the LED- it show 4V constant.

[buchman]

Re: LG47LA621Y LED TV screen flashes onse

Do you have all the expected voltages on power supply?

Yes

[diif]

Re: LG47LA621Y LED TV screen flashes onse

Faulty LED/s.

[buchman]

Re: LG47LA621Y LED TV screen flashes onse

Faulty LED/s.

How can I know what kind of LED do I have without lifting the screen?
I want to buy them first and then to disassemble the tv.

I don't want to buy the whole strip, I want to buy smd LED and solder myself.

[vinceroger69]

Re: LG47LA621Y LED TV screen flashes onse

what is the lcd panel number thats used in this set we can then check and see if it tells us the led strip numbers etc

[buchman]

Re: LG47LA621Y LED TV screen flashes onse

what is the lcd panel number thats used in this set we can then check and see if it tells us the led strip numbers etc

I think this is it.

[Andrew F. Ali]

Re: LG47LA621Y LED TV screen flashes onse

Since you want to replace the LEDs and not the entire strips, you could get the 3V Cool White LEDs very cheap before hand. They are basically universal LEDs that work on almost every set I've had to replace LEDs on the strips. I have found though that the other 'original ' LEDs fail soon after. I would therefore recommend replacing the entire strips if you don't want repeated failure.

[vinceroger69]

Re: LG47LA621Y LED TV screen flashes onse

These are the leds i have been using myself
https://www.aliexpress.com/item/100p...669016320.html
this video looks like it maybe the same strips as used in your tv
https://www.youtube.com/watch?v=dhAs0mb1_pQ

[buchman]

Re: LG47LA621Y LED TV screen flashes onse

These are the leds i have been using myself
https://www.aliexpress.com/item/100p...669016320.html
this video looks like it maybe the same strips as used in your tv
https://www.youtube.com/watch?v=dhAs0mb1_pQ

Yup, looks like exactly tv as mine.

The question is what is the current and voltage and the size of the LED should be?

[vinceroger69]

Re: LG47LA621Y LED TV screen flashes onse

budm im sure will confirm i got these from a link he posted a while ago.
The size of the led i have found matches all the lg sets i have repaired so far, until you strip your panel down and remove a faulty led of your strip and measure it maybe hard to tell exactly, but ive never had a issue using these not sure if diff used these himself either, the hardest part i find sometimes is lining back up the diffuser over the led.

[diif]

Re: LG47LA621Y LED TV screen flashes onse

These are the ones I have https://www.aliexpress.com/item/100P...484083505.html
They look the same as you posted. Their specs are a little off though.
At 3V it draws 140mA, at 3.6V it draws 500mA
They are also not the identical whiteness to the originals. Only very slightly off but it is off.

Superglue Gel is great for sticking the lenses back on. I leave the boards connected to the back of the TV and just remove the LCD and plastic layers. That way the lens alignment and LEDs can be verified before the LCD is put in place.

[budm]

Re: LG47LA621Y LED TV screen flashes onse

LATWT470RELZK
is the LED I used for LG panel.
The more current is forced through the LED the higher Vf it will be.

[vinceroger69]

Re: LG47LA621Y LED TV screen flashes onse

these are the ones budm mentions and same part number diff uses too
https://www.aliexpress.com/item/100p...ceBeautifyAB=0

[thoma]

Re: LG47LA621Y LED TV screen flashes onse

http://www.berlin-repariert.de/lg-47...-bild-nur-ton/