LG 42LA620V Backlight Voltage Help

[Bloopeta]

Hi, I have an LG 42LA620V with a backlight issue, when powered on the logo flashes up briefly then screen goes off, sound still present. I am trying to diagnose whether its the LEDs or the board, could anyone tell me what the voltage output from LED+ etc from the board should be please?

Thanks in advance

[Andrew F. Ali]

Re: LG 42LA620V Backlight Voltage Help

In a darkened room with an input so you hear the audio flash atorch light on the screen and see if you can make out the faint image. As with most of the LGs we are seeing it is a backlight issue as they set the backlight level to 100 and overdrive the LEDs causing premature failure.

[Bloopeta]

Re: LG 42LA620V Backlight Voltage Help

Hi, thanks fpr your reply, sorry I should have mentioned I have already done flashlight test and screen is visable, just need to determine now if its the board or the LED strips at fault, amd was wanting to know the voltages to test the board before I have to remove the screen to test LEDs

[Andrew F. Ali]

Re: LG 42LA620V Backlight Voltage Help

Voltage tests will help us to determine your issue. We need the voltage at start-up and when it settles with the RED probe on the +ve LED connector pin and the BLACK on chassis GND and the voltage at start-up and when it settles with the RED probe 0n the -ve LED connector pin and the BLACK on chassis GND.

[Bloopeta]

Re: LG 42LA620V Backlight Voltage Help

I have attached a photo of LED plug, readings from left to right are -

Startup Settled

Led+ 165 led+ 57.8
Led - 0 led- 0
Led+ 74 led+ 57.7
Led -29 led- 13.2

[Andrew F. Ali]

Re: LG 42LA620V Backlight Voltage Help

OK. Your readings indicate bad LEDs. Do you know how to tear the Panel down to the LEDs to replace them?

[Bloopeta]

Re: LG 42LA620V Backlight Voltage Help

Yeah ive done some before on a hitachi, thanks so much for all your help, much appreciated.

[Andrew F. Ali]

Re: LG 42LA620V Backlight Voltage Help

Please do keep us posted on your progress. Thanks.

[Bloopeta]

Re: LG 42LA620V Backlight Voltage Help

Hi, I stripped TV down today and tested strips, there was 1 bulb out on an R2 strip, and there was another Full R2 strip out, and a full L2 strip out, have ordered parts and awaiting delivery.

Ive also picked up a 42" panasonic today that keeps doing a self check, I will start a new thread regarding this.

[yohnsee]

Re: LG 42LA620V Backlight Voltage Help

Hello,
you do yourself a favor, when you change all the strips in this case.
As I read your lines, I think it was your idea also.
A few weeks ago I had to replace the whole backlight module in an LG Tv, because only 1! led survived the following disaster:

Interesting fact: in this tv they didn't use their own screen, it was something Heesung or similar. Yet another evidence on using the LED backlight on 100% 24/7.

[Andrew F. Ali]

Re: LG 42LA620V Backlight Voltage Help

I have found from previous experience that if you have to change LEDs and strips that you should not just change the bad one/s alone. I will recommend changing ALL of them so that when it works after a few months you do not get a repeat failure of LEDs.