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Old 01-28-2022, 03:23 PM   #21
Scoff
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Default Re: LG55UB850V no picture or audio - flashing LED's help please?

OK so as the tv will no longer turn on from standby, I will need to take the back off again and unplug the WiFi module. Then I can power it back on and get Into the normal TV menu where WiFi settings will be greyed out. Then I will power off the TV from the wall and not the RC.
Once off I will reconnect the WiFi module and hope that the TV turns on again. If it does, I will perform the IN_STOP hard reset with the WiFi module plugged in to reset the MAC and see if I can then disable the Bluetooth from the normal TV menu once it hopefully boots up again.
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Old 01-28-2022, 03:42 PM   #22
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Default Re: LG55UB850V no picture or audio - flashing LED's help please?

Quote:
Originally Posted by Scoff View Post
OK so as the tv will no longer turn on from standby, I will need to take the back off again and unplug the WiFi module. Then I can power it back on and get Into the normal TV menu where WiFi settings will be greyed out. Then I will power off the TV from the wall and not the RC.
Once off I will reconnect the WiFi module and hope that the TV turns on again. If it does, I will perform the IN_STOP hard reset with the WiFi module plugged in to reset the MAC and see if I can then disable the Bluetooth from the normal TV menu once it hopefully boots up again.
yes correct.. but you need to do instop as you did before first.... disable bluetooth can be done by customer menu setting so the option will be available when the combo module installed.
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Old 01-28-2022, 04:15 PM   #23
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Default Re: LG55UB850V no picture or audio - flashing LED's help please?

OK now I'm confused. Even with the WiFi module disconnected, the tv will no longer turn on out of standby. It is doing the same as I posted about originally - 3 standby light flashes but the screen does not turn on. So perhaps unplugging the wifi module previously was just coincidence when it started working? Nothing else has changed. I can no longer attempt another IN_STOP as even with the WiFi module disconnected the TV no longer switches on.

I'm starting to think the tv needs to be on for some time allowing something to warm/heat up on one of the power or logic boards before it then starts working. Possibly bad BGA solder balls on one of the chips on the logic board? I notice even when the screen does not turn on, the chips on the logic board start to get warm after a while, so perhaps this is when it starts to work...

Last edited by Scoff; 01-28-2022 at 04:59 PM..
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Old 01-28-2022, 04:46 PM   #24
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Default Re: LG55UB850V no picture or audio - flashing LED's help please?

i am the one should be confused when you stated with photo at yours post #19 it show tv on with out module !!!

there are some things wrong with yours doing.. again
1- module out and no source or cable tv insert in tv... turn on if it come on do next

2- send IN_STOP now leave it to restart and screen go on..... do another instop when it go to start reboot plug it out from wall socket.

plug back your module and turn if it turn on sent instop again..

4 after it start and you set it go to menu and disable the bluetooth
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Old 01-28-2022, 04:58 PM   #25
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Default Re: LG55UB850V no picture or audio - flashing LED's help please?

[QUOTE=Diah;1103860]i am the one should be confused when you stated with photo at yours post #19 it show tv on with out module !!!

there are some things wrong with yours doing.. again
1- module out and no source or cable tv insert in tv... turn on if it come on do next

Module is out, no sources or anything else plugged in, but the tv will NOT turn on anymore. This is why I am confused. This resulted in the tv working previously, however it no longer turns on

Last edited by Scoff; 01-28-2022 at 05:00 PM..
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Old 01-28-2022, 05:13 PM   #26
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Default Re: LG55UB850V no picture or audio - flashing LED's help please?

Quote:
Originally Posted by Scoff View Post
no longer turns on
explain more in detail.. do you have the front status led blinked or what goings on when you turn on the tv... it could your tv only with RC start... not direct with plugging in wall socket. ( called last state power on off )
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Old 01-28-2022, 05:47 PM   #27
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Default Re: LG55UB850V no picture or audio - flashing LED's help please?

So currently the wifi module is unplugged, and the mains lead is connected to the socket. No other connections are present.

Test 1)
Starting with the tv mains socket turned off. I turn on the mains socket and then the tv front red standby LED is constantly illuminated. The tv is correctly in standby mode.
I press the power button on the RC and the red standby LED does 3 slow flashes and then the red standby LED turns off. The screen should now be illuminated but it is not on, no LG logo, nothing.

Test 2)
If I start with the tv mains socket turned off, then turn the mains socket on, the front red standby LED is constantly illuminated. The tv is correctly in standby mode. If I press the joystick button on the bottom of the tv, which performs the same function as the OK button in the RC, the same thing happens - the red standby LED slowly flashes 3 times and then turns off. The screen should now be illuminated but it is not on. There is nothing on the screen, no LG logo, nothing.

So this is the exact same behaviour as in my original post #1.
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Old 01-28-2022, 05:56 PM   #28
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Default Re: LG55UB850V no picture or audio - flashing LED's help please?

Quote:
Originally Posted by Scoff View Post
So currently the wifi module is unplugged, and the mains lead is connected to the socket. No other connections are present.

Test 1)
Starting with the tv mains socket turned off. I turn on the mains socket and then the tv front red standby LED is constantly illuminated. The tv is correctly in standby mode.
I press the power button on the RC and the red standby LED does 3 slow flashes and then the red standby LED turns off. The screen should now be illuminated but it is not on, no LG logo, nothing.

Test 2)
If I start with the tv mains socket turned off, then turn the mains socket on, the front red standby LED is constantly illuminated. The tv is correctly in standby mode. If I press the joystick button on the bottom of the tv, which performs the same function as the OK button in the RC, the same thing happens - the red standby LED slowly flashes 3 times and then turns off. The screen should now be illuminated but it is not on. There is nothing on the screen, no LG logo, nothing.

So this is the exact same behaviour as in my original post #1.
so at this state you need to look at the audio optical port on main boards if it lit red and remain lit after this 3 flash led of status led..
i
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Old 01-29-2022, 06:11 AM   #29
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Default Re: LG55UB850V no picture or audio - flashing LED's help please?

OK looking at the optical port, when the tv is in standby the optical port is not lit. When the tv is powered on by either RC or joystick button in tv, and the front red status led flashes slowly 3 times, the optical port is not lit. After the 3 slow flashes of the front status led, and the front red status led goes off (the screen should now be on but isnt), the optical port is not lit.

So no activity on the optical port at all anymore.

I tried leaving the tv on standby overnight to see if it made any difference this morning. Sadly no change.

Last edited by Scoff; 01-29-2022 at 06:47 AM..
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Old 01-29-2022, 06:50 AM   #30
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Default Re: LG55UB850V no picture or audio - flashing LED's help please?

if you didn't change by mistake any value at service menu.. then it seem you don't have 12V going out from power boards to mainboards... you need to measure voltage on the PCB sockets.
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Old 01-29-2022, 07:04 AM   #31
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Default Re: LG55UB850V no picture or audio - flashing LED's help please?

No I didn't change anything in the service menu at all, I only pressed IN_START in order to see the total hours usage, and took those pictures for reference and then exited.

When I first unplugged the wifi module after your original suggestion, the screen turned on correctly so it seemed to indicate this module was at fault, or it was causing a fault on the logic board.
However I think this was just a coincidence because even with it unplugged now, the screen no longer comes on. This indicates to me that the issue is intermittent. There may be an issue with the wifi module, which the IN_STOP hard reset may resolve, but there seems to be a separate issue with power from the power board to the logic board.

I tested all the voltage at the 28 pin power supply board connector originally before creating this forum thread and they were all correct at that time.
I will measure them all again now and report back. Thank you for your help so far by the way, appreciated!
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Old 01-29-2022, 07:48 AM   #32
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Default Re: LG55UB850V no picture or audio - flashing LED's help please?

For testing, all I have connected is the 240v mains power cable going into the tv. I have disconnected the 28 pin connector that goes from the power supply board to the logic board.



I have checked all 8 of the GND pins and they all have continuity to the chassis of the TV.
I have checked all 3 of the standby voltage pins, and they all read 3.550v.
I have checked all of the 12v and 24v pins, but they all show 0v.
Is this expected behaviour without the 28 pin connector plugged in? Or should I be getting 12v and 24v from the pins without having the 28 pin cable connected?
This is all I have connected at the moment:

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Old 01-29-2022, 08:16 AM   #33
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Default Re: LG55UB850V no picture or audio - flashing LED's help please?

not this way.. however we do know now the standby okay
put the black probe on chassis and the red probe on the jumper J71 ( this test point to measure 12V. and Jumper J75 for 24 V.)
while your probe on one of them turn on the TV and tell what yours DM will read during the led flash and no led.
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Old 01-29-2022, 08:32 AM   #34
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Default Re: LG55UB850V no picture or audio - flashing LED's help please?

also remove yours black stand this is absolute wrong no way to put it on chassis with out the back cover in place .. you may have short on T-CON or the the T-CON 12 v. cable disconnected under this dams stander.
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Old 01-29-2022, 08:40 AM   #35
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Default Re: LG55UB850V no picture or audio - flashing LED's help please?

TV on standby with red status light on solid. Probe on J71 shows 0v.
When I press the power button on either tv or RC, and the red front status LED flashes slowly 3 times, the reading increases to 11.71v and stays there. Once the front red status LED stops flashing and goes out (tv screen should be on but isn't), the probe continues to read 11.71v.

TV on standby with red status light on solid. Probe on J75 shows 0v.
When I press the power button on either tv or RC, and the red front status LED flashes slowly 3 times, the reading increases to 24.1v. Once the front red status LED stops flashing and goes out (tv screen should be on but isn't), the probe continues to read 24.1v.
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Old 01-29-2022, 08:47 AM   #36
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Default Re: LG55UB850V no picture or audio - flashing LED's help please?

PCB are fine and firmware main boards fine too do what i wrote on post #34
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Old 01-29-2022, 08:47 AM   #37
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Default Re: LG55UB850V no picture or audio - flashing LED's help please?

Quote:
Originally Posted by Diah View Post
also remove yours black stand this is absolute wrong no way to put it on chassis with out the back cover in place .. you may have short on T-CON or the the T-CON 12 v. cable disconnected under this dams stander.
Perhaps the angle of the previous pictures made it look like there was contact, however the stand is stood off of the tv by an inch or more and there is absolutely nothing in the way of cables or pcb touching the metal stand.



I will however remove the stand from the tv for continued testing.
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Old 01-29-2022, 08:57 AM   #38
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Default Re: LG55UB850V no picture or audio - flashing LED's help please?

the TV turning on.. because 12V & 24V remain ON and stable.. in this case the Optical audio port 100% should lit red on.. ( you said no ) the screen you have black.. 1- could be the LED BL went bad after IN_STOP because it will bring back the BL as factory setting and you may had before reduced them before to 50% so they lasted with TV life hours 16500.
2- if the BL are fine.. we have problem could be the T-CON cable 12V not correct or the Fuse F1 on T-CON went open.. this had nothing to do with IN_STOP

edit: so after you check the T-CON cable and the F1 Fuse of it from both side it should have 12V. the black probe to chassis always. if this are correct then you need to turn on the tv and press menu and use torch light to see if the menu can seen on the screen. also your tv should response to RC

Last edited by Diah; 01-29-2022 at 09:04 AM..
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Old 01-29-2022, 09:32 AM   #39
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Default Re: LG55UB850V no picture or audio - flashing LED's help please?

The optical audio port is not lighting up at any point from when the tv is in standby mode, through the 3 slow front re status LED flashes, or when the front red status LED goes out (when the tv screen should be on but isn't). There is no sign of life on the optical audio port at all.

I have tested fuse F1 on the T-Con board for continuity and it is ok.
With the tv in standby and the red front status LED on, there is 0v on both sides of fuse F1.
When I try to power on the TV from the tv button or the RC, during the 3 slow front red status LED flashes, the voltage present at either side of fuse F1 on the T-Con board gradually increases and settles at approx 0.835v. This reading of 0.835v remains when the front ref status LED stops flashing and goes out (when the tv screen should be on but isn't). The same reading shows at either side of fuse F1. Are you saying this should be 12v on either side of fuse F1?


Last edited by Scoff; 01-29-2022 at 09:43 AM..
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Old 01-29-2022, 09:42 AM   #40
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Default Re: LG55UB850V no picture or audio - flashing LED's help please?

Quote:
Originally Posted by Scoff View Post
reading of 0.835v remains when the front ref status LED stops flashing and goes out (when the tv screen should be on but isn't). The same reading shows at either side of fuse F1. Are you saying this should be 12v on either side of fuse F1?
0.835v not good at all..
let we do the following:
1- we test if the RC working.. while the set had 12V & 24V stable.. you know where you check on the jumbers we talked on before.. if yes use the RC to turn it off to standby. then turn it on again with RC. check the 12 & 24V again-- if you have them and the set can go to STBY and wake up again with RC... use yours service RC and send IN_STOP follow it with code 0413 and let it do what it should... check again 12 24 and the 12V on T-CON F1
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