55la6205 backlight issues

[speedymmx]

Hi, Guys:

I have this LG-|Smart TV and it just started having this issue:

when I turn it on, I get the LG logo and LED power light, it works for about 10 seconds and the back light/video goes black/LED power light goes out, sound keeps playing, I can see the image by doing the flashlight test, If I turn it off and on the same thing happens.

two days ago I unplugged the TV and left it alone all day, then I turned it on again and it worked perfectly for about 5 minutes with no issues........then it happened again so is either when it gets hot or something.

I removed the back cover and I can't see any bad caps or burn marks anywhere in the power supply/led board, any ideas as to what else to check???

Thanks

[budm]

Re: 55la6205 backlight issues

Please up load good clear pictures of the whole back side of the TV so we can see how all the boards are connected together for a start.

[speedymmx]

Re: 55la6205 backlight issues

Here they are:

[budm]

Re: 55la6205 backlight issues

So what DCV do you get on all 4 pins of the LED connector P801 with ref to the chassis GND when the backlights are on and when they go out?
Power supply-LED driver board:
LG EAY62810701 (3PAGC10124A-R) Power Supply LED Board
http://www.shopjimmy.com/lg-eay62810...pply-unit.htm#

[speedymmx]

Re: 55la6205 backlight issues

This is what I got:

When the backlight is on and working, showing the LG logo floating across the screen the DCV are as follows from left to right connectors

LED + 133.5
LED - 32.9
LED + 177.5
LED - 43.1

When the backlight randomly turns off the DCV are:

LED + 84.4
LED - 5.36
LED + 84.4
LED - 166.0 this readout goes up and down from 177 down to 166...

Thanks

[budm]

Re: 55la6205 backlight issues

There are two LED driver circuits and you have problem with one of the LED string. It looks like the one with L+ of 175.5V is the problem one.
Disconnect the LED connector and take the readings of both L+ aging to see how high the DCV goes to before it starts dropping down to 84V..
Pictures provided by shopjimmy.

[speedymmx]

Re: 55la6205 backlight issues

OK so I disconnected the LED cable and measured only the two L+ with the TV OFF as soon as the TV is turned on the DCV are:

L+ = 179 and then it starts dropping down to 84
L+ = 184 and then it starts dropping down to 84.4

[budm]

Re: 55la6205 backlight issues

OK so I disconnected the LED cable and measured only the two L+ with the TV OFF as soon as the TV is turned on the DCV are:

L+ = 179 and then it starts dropping down to 84
L+ = 184 and then it starts dropping down to 84.4

OK, you have the problem with the LED strings that are connected to the L+ that you were getting the 177V reading with LED strings connected to it. It was close to the high Voltage shutdown trip point of 184V.

[speedymmx]

Re: 55la6205 backlight issues

OK so if I order the replacement part which I believe is this one:

http://www.ebay.ca/itm/like/26211764...s=true&viphx=1

is there a tutorial or a video I can follow as to how to get to the LED strips?

also do I need to buy more than one LED strip????

Thanks

[budm]

Re: 55la6205 backlight issues

I would not order it by TV model number since same model may use more than LCD panel model. You need to get the model number of the LCD panel and find out how many LED strips there are inside what they look like. You do not know how many are bad yet.
One strip for $40?
Taking apart 55" panel is definite not for beginner.

[speedymmx]

Re: 55la6205 backlight issues

LA62M55T120V12 seems to be the LCD panel number

[budm]

Re: 55la6205 backlight issues

LA62M55T120V12 seems to be the LCD panel number

Then you need to find out from the seller if the LED strips are for that LCD panel. I will not order anything until you get to the LED strips first.

[budm]

Re: 55la6205 backlight issues

BTW, did you try lower the backlghts level down to like 50% in the user menu setup to see if the backlights will stay on longer?

[speedymmx]

Re: 55la6205 backlight issues

BTW, did you try lower the backlghts level down to like 50% in the user menu setup to see if the backlights will stay on longer?

Hi, No I haven't tried that yet, I will do it later today and post the results.

Thank you for all your help

[thoma]

Re: 55la6205 backlight issues

https://sites.google.com/site/lcd4ho...-led-backlight
regards thoma!

[speedymmx]

Re: 55la6205 backlight issues

BTW, did you try lower the backlghts level down to like 50% in the user menu setup to see if the backlights will stay on longer?

Ok so I tried as suggested with the backlight in setting of 5/100 and it did last longer as soon as I selected an app like youtube, it starts and then later the backlight goes out, I uploaded a video to youtube so everybody can see what exactly is happening.

Here is the link:

at 53 seconds in the video is when the backlight goes out.

https://www.youtube.com/watch?v=N0IP...ature=youtu.be


Thanks

[budm]

Re: 55la6205 backlight issues

At this point I am pretty sure you will need to replace the LEDs.

[speedymmx]

Re: 55la6205 backlight issues

At this point I am pretty sure you will need to replace the LEDs.

How can I test the LEDs??? should I just replace all the ones connected to that circuit by following the cable connector?

Thanks

[raster]

Re: 55la6205 backlight issues

Just a thought, try tightening the screws on the transistors/mosfet/diodes attached to the 2 heat sinks on power board. I had a similar thing and this sorted the issue.

[speedymmx]

Re: 55la6205 backlight issues

Just a thought, try tightening the screws on the transistors/mosfet/diodes attached to the 2 heat sinks on power board. I had a similar thing and this sorted the issue.

No changes after trying this still has the same issues.