Lg 55ln5100 backlight issue

[splatee]

Hey everyone, have another set that is acting a bit finicky.

It's a LG 55ln5100 that has random backlights issues and a problem syncing with HDMI (I think).

First the random backlight issue is sometime the set will work with no problem and then it will loose the picture but still have audio. I verified with a flashlight that there was still video. Also it seems to do it if you turn it off and right back on. If you let it sit for a bit it will work again. Now I first went and resoldered the caps on the power supply board and did not see any bulging caps. I have not checked voltages yet because the problem is random. I did however went and ordered a power supply/led driver repair kit from Shop Jimmy.

Now the HDMI sync issue is strange. When I use a blu ray player it syncs right up. But if I use my directv box it sits for awhile or it gets snowy and then it will display. Sometimes I have to turn off the box and back on for it to show up. Now I have not switched the HDMI cable yet.

Just trying to get a jump on troubleshooting it here first before I take it apart.

Thank you

[budm]

Re: Lg 55ln5100 backlight issue

I do not know about the HDMI problem but these LG LN5000 series are know for fail LEDs that will burn up spectacularly, so make sure to turn down the backlights level to as low as you can. Also poor solder joints around the rivet for component legs.
https://www.badcaps.net/forum/showth...ht=LG+47LN5790
https://www.badcaps.net/forum/showth...ght=lg+47ln%2A

[splatee]

Re: Lg 55ln5100 backlight issue

I do not know about the HDMI problem but these LG LN5000 series are know for fail LEDs that will burn up spectacularly, so make sure to turn down the backlights level to as low as you can. Also poor solder joints around the rivet for component legs.
https://www.badcaps.net/forum/showth...ht=LG+47LN5790
https://www.badcaps.net/forum/showth...ght=lg+47ln%2A

Yah I read some of the threads regarding the LED issue. Was not aware that it was the "LN" series at the time I picked up this set or I would have probably passed on it at the time. I have the backlight lowered to 15 I had it at 20 last night. Could you elaborate a bit more on what you mean by "poor solder joints around the rivets) ? Are you referring to the power supply? So far have had no issues with it this morning.

And this is the kit I bought from Shop Jimmy

https://www.shopjimmy.com/lg-eay6281...repair-kit.htm


Thank you

[budm]

Re: Lg 55ln5100 backlight issue

Power supply board. If you look at one of the leg of the big main filter cap you will see through hole rivet that the leg of the cap is soldered to, same for the transformer leg and also other semiconductor devices as well. When I work in these TV I always touch up the solder joints on those components. SAMSUNG boards have the same problem with poor solder joints.

Pictures provided by shopjimmy.
http://www.shopjimmy.com/lg-eay62810...pply-unit.htm#
LG EAY62810701 (3PAGC10124A-R) Power Supply / LED Board
http://www.shopjimmy.com/catalogsear...?q=Lg+55ln5100

[splatee]

Re: Lg 55ln5100 backlight issue

Power supply board. If you look at one of the leg of the big main filter cap you will see through hole rivet that the leg of the cap is soldered to, same for the transformer leg and also other semiconductor devices as well. When I work in these TV I always touch up the solder joints on those components. SAMSUNG boards have the same problem with poor solder joints.

Pictures provided by shopjimmy.
http://www.shopjimmy.com/lg-eay62810...pply-unit.htm#
LG EAY62810701 (3PAGC10124A-R) Power Supply / LED Board
http://www.shopjimmy.com/catalogsear...?q=Lg+55ln5100

Ok got it, thanks for the pic. I did go over the power supply board the other day but will check it again. I will post an update in a few days.

Thank you

[splatee]

Re: Lg 55ln5100 backlight issue

Well attempted fixing the power supply with the Shop Jimmy repair kit. I did not replace two surface mount ic chips due to their location and number of pins. I did not feel comfortable attempting it. Well tv showed the same signs as it did before and now my wife just said that there is no power at all. No red led light and tv does not power on. So either one of the other components I replaced failed or something else on the power supply went. Anyways I have ordered a replacement power supply and hopefully that will take care of the issue with the backlight and now no power. I wish I had known before about how problematic this series of LG tv's are, I would have passed on it probably.

Thank you

[splatee]

Re: Lg 55ln5100 backlight issue

Took power supply board out and found that one of the fuses that was replaced in the kit blew. I have the original one so I don't know if I am going to bother replacing it. I have a spare on the way so I will just swap it out. I don't want to risk damaging anything else.

[splatee]

Re: Lg 55ln5100 backlight issue

Replaced fuse and plugged in and no standby led. Checked replacement fuse and it was open. So at this time I will just wait for the replacement power supply.

[splatee]

Re: Lg 55ln5100 backlight issue

Well new power supply in and tv worked fine for about 4 hours and then picture went out but still had sound. Turned it off and back on and picture returned and has been going for about an hour now.

So I guess the next step is to check the leds for any bad ones and possible poor solder joints. I don't know what else it could be. Now if it is a bad led I do have led strips from a sharp aquos that o am wondering are comparable?

Thank you

[jeffer76]

Re: Lg 55ln5100 backlight issue

I have similar model. 55ln5200. Backlights flash at power on. Video and sound still good. Just no backlights. Took tv apart and tested the leds. Ran 18v across each led strip. They all lite perfectly.
Does anyone know what voltage is supposed to be developed by the LED Driver? This set runs two lines of leds.
I checked the upper set from chassis ground to LED+ and get 148v.
Lower set from chassis to LED+ is 171v. Seems odd since the upper set has more strips than the lower set.
Should I be measuring from LED- to LED+ ? Tried: Get 87.6v top set and 94.8v on lower set at moment of flash then 0v.

[jeffer76]

Re: Lg 55ln5100 backlight issue

SOLVED: Found bad connection linking the bottom two strips together. Resoldered connector and added jumper across strips.

[budm]

Re: Lg 55ln5100 backlight issue

When I do the repair on these LED strips, I always resolder those connectors too.

[jeffer76]

Re: Lg 55ln5100 backlight issue

Hope this helps someone else in the future.

[budm]

Re: Lg 55ln5100 backlight issue

That is one good way of fixing it.

[budm]

Re: Lg 55ln5100 backlight issue

The LN series are know for burning LEDs, so make sure to turn down the backlights level as low as you can.
https://www.badcaps.net/forum/showthread.php?t=54197

[102mm]

Re: Lg 55ln5100 backlight issue

Hope this helps someone else in the future.

This surely helped me, exact same issue. Thanks for the info.