Lg 42LE4500-ZA no backlight

[Gimi]

Hi everyone. Got my friends tv here trying to sorted but up to now costing money "as usual".
It is an LG 42le4500-za
It was showing logo and after that blank screen.
After reading on some truble people has had with this TV
and after having checked the voltages which apart from led failing once blank screen comes on,every other voltage it was fine.
So I thought could probably be led driver board so I got another power supply and having same problem but just noticed that the led lights are off but there is picture on TV
Now what is my next step plz? Thank you

[ReeceyBurger123]

Re: Lg 42LE4500-ZA no backlight

Can you rephrase that please ? So you checked the Led drive voltage and its missing ?

[Gimi]

Re: Lg 42LE4500-ZA no backlight

Can you rephrase that please ? So you checked the Led drive voltage and its missing ?

Yes. When I first turn tv on with multimeter on it shows 108v then when screen goes blank drops down to zero

[Gimi]

Re: Lg 42LE4500-ZA no backlight

Yes. When I first turn tv on with multimeter on it shows 108v then when screen goes blank drops down to zero

Sorry shows 102v then drops to zero

[Gimi]

Re: Lg 42LE4500-ZA no backlight

Any idea plz? Is it another faulty power suply (led driver) or my led's are bad? If led's are bad why does it works for a bit?

[budm]

Re: Lg 42LE4500-ZA no backlight

Can we see the whole back side of the TV? Pictures of the power supply LED driver board?
What DCV do you get for the BL-ON and the Dimming Control pins?

[Gimi]

Re: Lg 42LE4500-ZA no backlight

Hopefully I've loaded pictures as they bif files otherwise will go on pc

[Gimi]

Re: Lg 42LE4500-ZA no backlight

11.26 and 9.5v from the led connection black wires black w

[budm]

Re: Lg 42LE4500-ZA no backlight

https://www.badcaps.net/forum/attach...7&d=1459356019

Picture is too out of focus for me to read the model number of the board.

https://www.badcaps.net/forum/attach...8&d=1459356019
Can you please take the different angle so I can read the pin labels for both LED connectors P205 and P20??

This TV has 8 strings of LEDs with 8 LED drivers circuits so we need to check the DCV of each strings.

[Gimi]

Re: Lg 42LE4500-ZA no backlight

P/n: 3PCGC10008A-R

[Gimi]

Re: Lg 42LE4500-ZA no backlight

Just put back old power supply and exactly same thing. Dim display without backlight and voltages all the same.

[Hamie]

Re: Lg 42LE4500-ZA no backlight

If you pull out the wire BL DIM do the back lights stay on?

[Gimi]

Re: Lg 42LE4500-ZA no backlight

Which one exactly is bl dim wire? The 4 black wires from the led cables? Sorry for my ignorance knoledge

[budm]

Re: Lg 42LE4500-ZA no backlight

Based on the pictures, you need to check the DCV on those pins.
The DCV at A, F, G, and L should show about the same DCV.
The DCV on B, C, D, E, H, I, J , K (these should be the LED strings Cathode returns) you will have to leave the red probe (black probe on the chassis) on B then turn the TV on and record the DCV reading, then turn the TV off and then move the red probe to C and do the same thing again, eight readings you need to do.
I still need the pictures so I can read those pin names.

[budm]

Re: Lg 42LE4500-ZA no backlight

BTW: P/n: 3PCGC10008A-R is for the black PCB number, the PCBA is on the barcode sticker on the board (not on the sub LED driver board).
Pictures provided by shopjimmy.

Your PCBA has 8 drivers, the pictures attached has 12 drivers.

LG PCBA EAY60803101 (3PCGC10008A-R) Power Supply / LED Board fitted with 12-string drivers.

[Gimi]

Re: Lg 42LE4500-ZA no backlight

These are all part numbers on my board.
In UK here and spent £50 on that board. Just wanting to know if that is also faulty so I could send it back. Unles I need to take screen apart and check the led's are ok but why would they come up if they were faulty?! Thanks for helping out anyways.

[budm]

Re: Lg 42LE4500-ZA no backlight

These are all part numbers on my board.
In UK here and spent £50 on that board. Just wanting to know if that is also faulty so I could send it back. Unles I need to take screen apart and check the led's are ok but why would they come up if they were faulty?! Thanks for helping out anyways.

That is why I gave you the instruction to read those Voltages on the LED connectors.
And if you loo k to the left of the black connector P201 you will see the chart showing which pins are for.
Looking at the top side of the board you will see the ODD pins assignment.
For example PIN 1 is PWR-ON, PIN 3 is 20V, PIN 5, 7 are GND, PIN 9, 11 are 3.5V

Pin 18 is DRV_ON (BL-ON), Pin 22 is PDIM1.

[Gimi]

Re: Lg 42LE4500-ZA no backlight

I have just done that. There is very changeable.
First reading is when aply power on then 2nd reading when led's are on then 3Rd reading when led's turn off

[budm]

Re: Lg 42LE4500-ZA no backlight

Look at you B (2) reading of 1.6V compared to the 7 readings (2).
I would say you have LED problem.

[Gimi]

Re: Lg 42LE4500-ZA no backlight

The p201 voltages are correct