LG TV sound no picture, boards replaced

[heathloder]

Re: LG TV sound no picture, boards replaced

Just came across one of these today (LG 43UJ6200) whose backlight was turning off immediately upon power on (flashlight test revealed it was the backlight and not the whole display).

LED tester revealed open on LED string number 2. Opened chassis - LED tester found one bad strip (2nd strip from the top on the "right" if you are looking at the LED's from the front). Checked each LED - only one LED was found to be open Literally ONE LED preventing this beautiful set from booting.

Just wanted to report here that another one of these models started exhibiting these same symptoms, and turned out to have an LED issue.

[nomoresonys]

Re: LG TV sound no picture, boards replaced

Another one saved, nice work.

[voltman]

Re: LG TV sound no picture, boards replaced

I found out like neilc6 said, when I run the photo/capture app. the backlight reverts back to the 90 default setting. I use this app to view pics and occasional home movies on a USB drive. When I use this app, I solve the problem by putting it on energy saver . My energy saver has 3 settings, “min”, “med”, and “maximum”. I put it on “minimum”. The backlight setting number does not work on the energy setting, but I estimate it to be about 60 on minimum. When I shut the energy saver off, it reverts back to my user settings. This is easy enough to live with.

One thing, when testing the power board at the two LED outputs, with the LED's disconnected, I used two different multimeters. The cheap craftsman was not fast enough to read the peak voltage before the board would shut down. All the readings I got were inconsistent and varied a lot. I used an older Fluke multimeter and it would read 25VDC before shutting down. The specs are Minimum 51.4 VDC at each channel. The Fluke was also inconsistent and varied. I don't know if 3 of the LED's blowed and caused the power board to burn up or the other way around.

Many thanks to Badcaps forum, budm, nomoresonys, neilc6 and everyone here who took the time to help me. I was able to fix my TV and learned something while doing it. I hope this thread might help others with the same or similar problem.

[neilc6]

Re: LG TV sound no picture, boards replaced

I believe the firmware updates set the the tv defaults to ECO mode with 70 backlight level. Apps may still run at 100% backlight in Standard mode (access through quick menu). I would run the tv at 60 backlight max. Samsung levels are between 1-20.

[voltman]

Re: LG TV sound no picture, boards replaced

Thanks nomoresonys. There is a part of the update called:3. Release History
[03.50.50]
1. Improve the backlight turn-on failure

Since the problem with this set was the LED's burned out (the power board also burned up) I thought maybe there was something in this update other then turning the backlight down, that might prevent premature LED failure.


Budm I am adjusting "Backlights". My settings go 0 -100 The factory default setting was 90. I got the brightness on factory setting of 50.

My settings now:

Backlight 75
Contrast 87
Brightness 50
Sharpness 26
Color 60
Tint 0

TV viewed mostly in artificial light

[budm]

Re: LG TV sound no picture, boards replaced

Can you guys give me a recommended setting for the backlight? It seems factory setting is 90. I disabled auto picture and energy saver and got the backlight at 75 right now. Trying to avoid typical LG LED early death.

With the backlight setting turned down, is it really necessary to update the firmware? I do not use the TV with internet. Only other function I use is DVD / Blueray. Thank you for your help.

Are you adjusting the BACKLIGHTS level or the Brightness level? My LG TV's BACKLIGHTS are 0 ~20, The Brightness is 0 ~ 100.

[nomoresonys]

Re: LG TV sound no picture, boards replaced

As low as you can stand it, I have mine on 5, it goes up to 20, you don't have to update, a lot of people only update if they are having a problem that might be fixed by it, plus some updates can be buggy so I try not to update at least til the update's been out for a while and there's no bad feedback from users.

[voltman]

Re: LG TV sound no picture, boards replaced

Can you guys give me a recommended setting for the backlight? It seems factory setting is 90. I disabled auto picture and energy saver and got the backlight at 75 right now. Trying to avoid typical LG LED early death.

With the backlight setting turned down, is it really necessary to update the firmware? I do not use the TV with internet. Only other function I use is DVD / Blueray. Thank you for your help.

[nomoresonys]

Re: LG TV sound no picture, boards replaced

You got a new power board right? so get the strips and see if that does it.

[voltman]

Re: LG TV sound no picture, boards replaced

No smokers in house. Sent you a IM

[neilc6]

Re: LG TV sound no picture, boards replaced

You can get black soot on boards if the tv is in a home with a heavy smoker.

[voltman]

Re: LG TV sound no picture, boards replaced

The black soot seems to have originated at the center, and possibly the upper right corner (look at the soot deposit on that blue component) of the power board, even though there are not any visible signs of bad components. The capacitors all "look" good. The center of the power board shows soot and also at the center of the back of the power board. This is all black soot which easily wipes away. The main board is clean. The front LED area was absolutely clean, not a smudge.

[dick_barton]

Re: LG TV sound no picture, boards replaced

I was shocked to not find anything burned up. The wiring and all the LED's look pristine.

But something has definately burnt out with all the soot. It's even on the Varistor by the mains input where it says HOT on the upper side of the power supply.

[nomoresonys]

Re: LG TV sound no picture, boards replaced

Set there for 29 bucks, see if that's a match: https://www.ebay.com/itm/LG-LED-Stri....c100010.m2109

[neilc6]

Re: LG TV sound no picture, boards replaced

You have an open LED in the top half causing the whole string not to light up. Tougher to isolate but you can use a multimeter in diode mode and check every LED or swap each non lit strip into the working string. Can replace only the bad strip but all the LEDs have wear and could fail in the future. You need to turn down the backlight level on all inputs and all smart apps after repair. Top and bottom strings are probably wired separately so the backlights flashed from only the bottom string. I think I have a full set of strips for this model (from new cracked screen tv) for this model on ebay (check the part number printed on the strip).

[voltman]

Re: LG TV sound no picture, boards replaced

I have an update on my LG4300

I removed the screen, many thanks to nomoresonys, the video you gave me was very helpful. I was shocked to not find anything burned up. The wiring and all the LED's look pristine. I powered up the set without the screen and the top two rows of LED's are out. So only the bottom 18 are working. Nothing visibly notable about the top 18. Is it common for two whole rows to go out at once? Whatever burned up has to be on the power board or main board. Both have been replaced

I understand that when any LED's burn out the power will shut down and you get nothing or rather no picture just sound. Powering up the set without the screen per neilc6 suggestion has shown me which ones are out. I intend to test the bad strips to confirm. Your thoughts, suggestions, and how to procede from here would be much appreciated.

[voltman]

Re: LG TV sound no picture, boards replaced

Very informative neilc6, thank you. Nomoresonys, I think you might be right about the money pit. Been watching the videos and feel confident about the tear down now. Question. I know something had to burn up. If the reflector is burnt and or any of the layers of diffusion are burnt or stained, is the set still repairable? Will a slight burn mark effect the picture quality? What is and is not acceptable here? Cannot believe I researched before buying and got stuck with this junk. TV is only 22 months old!

[nomoresonys]

Re: LG TV sound no picture, boards replaced

I'd strip it down to leds, it's a 43, shouldn't be a problem if you take it slow, it's usually the big screens that break. Being rebadged chinese tho, odds are the bga will go to hell shortly, you may have a money pit there.

[neilc6]

Re: LG TV sound no picture, boards replaced

You need to video the flash with the panel removed. See my blog post here

http://techhometravel.com/lg-ln-seri...ed-backlights/

[voltman]

Re: LG TV sound no picture, boards replaced

Tried video taping the split second flash. It is really fast. The "LG" and "lifes good" (not anymore) does not look right. Is this possibly what only a few working LED's might look like when flashed? These are stills captured at the best frame of video.