LG55UB850V no picture or audio, just flashing LED's help please?

[IAmOrion]

Hi members, I came across this forum when searching a fault on my LG 55UB850V TV.
Rather than hi-jack another members post/thread I thought I should start my own even though it's an almost identical issue.

The thread I refer to can be found here:
https://www.badcaps.net/forum/troubl...-s-help-please

My boards are the same, and my issue it the same. I have NO Picture and NO Sound. Nothing. When first turning on the TV at the mains sockets, the RED LED turns on and stays on solid in standby mode.
When I press the power button on the remote (or trigger it via the joystick thing underside of LG logo and red led), the red led flashes 3 times, then turns off. Then nothing happens, ever.

Here's photos of my boards:








With the back removed, LED LD1900 on the main logic board lights up briefly for around 1 seconds, then turns off.
LED LD2300 remains solid red
After about 1 minute or so, LED LD701 on the power board flashes 5 times in a row, then about a 5 seconds pause, then repeats the 5 second flash. This repeats itself indefinitely.

Fuse F1 on the Display board (aka T-CON as I've come to learn) only give me around 0.835v

J71 reads 11.8v, J75 reads 23.8v

I don't have a service remote, I used my Flipper Zero to try the IN_STOP commands using this file: https://github.com/Lucaslhm/Flipper-...828_Service.ir

Whilst the Power and P-ONLY commands visibly work, IN_STOP doesn't appear to do anything. I have ordered what I think is the correct service remote (just in case flipper isn't sending command correctly or it's wrong)


I'm hoping this is the correct service remote!

I've tried holding the tactile switches for 10 seconds whilst turning on etc but to no avail either.

My Optical Audio socket DOES have a RED LED lit up on it.

I have tried all the tests with and without the WiFi/BLE module attached again to no avail.

Now, the only difference so far compared to that existing thread, is that PIN 18 of my 26 PIN connector is 0v. All other recommended to test pins are correct (8, 12, 14, 20, 22)

I also unplugged the to connection at bottom of display board (I presume it's panel connection if I read correctly?) but the Fuse F1 was still at 0.835v.

I've unplugged, re-plugged, cleaned, re-seated, all connections. I've removed each board and cleaned behind them etc.




I have not yet tested the 5v USB output, I ran out of time today. Next day I will have free time again will be Tuesday 30th so hoping there may be some replies to give me things to test and check / try.

Many thanks in advance

[wylde]

OK - I am summarizing these as my problem was exactly the same as the post#1 on your post and the reference post #1 https://www.badcaps.net/forum/troubl...-s-help-please ---------------- I am coming in at post number 176 on page 9 on that larger thread ------------

THIS IS A MAINBOARD PROBLEM. In 2025 these TVs and boards now have been here a loooong time and so can be hit and mix with caps , chip movements etc... any repair too involved makes near no sense financially as a new 55" TV is 500 Euro - so spending more than for me 150 EURO max would make no sense as any other components could fail. Power board priced at about 45, t conn 50, mainboard 80 (range to 250 euro for greedy sellers) screen/LCD ??? backlight ??? so it can quickly add up. So the only reasonable repair for me would be OPTION 2.
Checking all the other components is helpful in ruling out elements but can be deceptive if you find anomalies in readings and can lead into other false paths where there is actually no problem.
I found a solution that many people with medium electronics background may be able to repair.

Option 1.
-------
If you have the exact same problem as post#1 - the most direct repair is to replace the mainboard- yes hard to find , or send the mainboard off to have the flat chips under the heatsinks heated and reflowed.

Option 2.
--------
If you have the exact same problem as post#1 - you can reflow it yourself I will outline what I used and an explanation in the next post - this is not exceptionally hard , I used a good quality heat gun(not even electronics grade) with temp setting and and aluminium tape / masking tape as well as flux and solder (the solder was not used on the board only used to get a gauge for the heat need to melt the solder and dial in the time and heat setting for the heat gun for me it was 300 degrees celcius and less than a minute - using the flux around each chip to determine when to stop)- probably the hardest part is unsoldering and removing the heatsinks and putting them back in place. I DID NOT FEEL CONFIDENT DOING THE BAKE TECHNIQUE - reason being there are so many plastics and micro caps and components that baking could damage and start another set of problems.

OVERVIEW
---------
Some of the other solutions outlined on the 9 pages are way too involved for me so I will outline what I have learnt after about 10hrs of reading, watching video repairs etc. SPECIFIC LG tvs and specifically these models can have multiple false ideas to problem check and can be difficult to rule out other faulty components so I will outline on what I have found on next post. I am sure the PROS have know what to look for but I was coming from very little experience only having 2 TV repairs under my belt.

my setup / problem - I used Option 2. to repair.
-----------------
exact same problem as post#1
tv model: 55UB850V-ZD
outer casing model 55UB850V-ZD.BEUWLJP
mainboard model: EAX65684604 (1.0)
mainboard sticker: MJM48164B300287 287216546 55UB850V-ZD.BEEWLJP EBT63083605

[IAmOrion]

OK - I am summarizing these as my problem was exactly the same as the post#1 on your post and the reference post #1 https://www.badcaps.net/forum/troubl...-s-help-please ---------------- I am coming in at post number 176 on page 9 on that larger thread ------------

THIS IS A MAINBOARD PROBLEM. In 2025 these TVs and boards now have been here a loooong time and so can be hit and mix with caps , chip movements etc... any repair too involved makes near no sense financially as a new 55" TV is 500 Euro - so spending more than for me 150 EURO max would make no sense as any other components could fail. Power board priced at about 45, t conn 50, mainboard 80 (range to 250 euro for greedy sellers) screen/LCD ??? backlight ??? so it can quickly add up. So the only reasonable repair for me would be OPTION 2.
Checking all the other components is helpful in ruling out elements but can be deceptive if you find anomalies in readings and can lead into other false paths where there is actually no problem.
I found a solution that many people with medium electronics background may be able to repair.

Option 1.
-------
If you have the exact same problem as post#1 - the most direct repair is to replace the mainboard- yes hard to find , or send the mainboard off to have the flat chips under the heatsinks heated and reflowed.

Option 2.
--------
If you have the exact same problem as post#1 - you can reflow it yourself I will outline what I used and an explanation in the next post - this is not exceptionally hard , I used a good quality heat gun(not even electronics grade) with temp setting and and aluminium tape / masking tape as well as flux and solder (the solder was not used on the board only used to get a gauge for the heat need to melt the solder and dial in the time and heat setting for the heat gun for me it was 300 degrees celcius and less than a minute - using the flux around each chip to determine when to stop)- probably the hardest part is unsoldering and removing the heatsinks and putting them back in place. I DID NOT FEEL CONFIDENT DOING THE BAKE TECHNIQUE - reason being there are so many plastics and micro caps and components that baking could damage and start another set of problems.

OVERVIEW
---------
Some of the other solutions outlined on the 9 pages are way too involved for me so I will outline what I have learnt after about 10hrs of reading, watching video repairs etc. SPECIFIC LG tvs and specifically these models can have multiple false ideas to problem check and can be difficult to rule out other faulty components so I will outline on what I have found on next post. I am sure the PROS have know what to look for but I was coming from very little experience only having 2 TV repairs under my belt.

my setup / problem - I used Option 2. to repair.
-----------------
exact same problem as post#1
tv model: 55UB850V-ZD
outer casing model 55UB850V-ZD.BEUWLJP
mainboard model: EAX65684604 (1.0)
mainboard sticker: MJM48164B300287 287216546 55UB850V-ZD.BEEWLJP EBT63083605

Thanks for the response - For the record, this post is 1 year and 8 months old.

I reflowed it myself 1 year and 8months ago (ish) using an oven! It's been working ever since without issue

I appreciate the response though as other users now and in the future will find it useful.

All the best