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

[Scoff]

Re: LG55UB850V no picture or audio - flashing LED's help please?

I have no experience with fixing TVs or electronics as such, and this fault doesn't really seem logical to me, based on the fault pattern displayed since the very start. Either an intermittent fault, more than one fault, or some 'Red herrings' getting in the way during testing.

I have triple checked all 6 ribbon cable ends under the magnifying glass to check the gold pin condition and I cannot see anything physically wrong with any of them. No damaged pins and no shorts/touching pins etc. All look 100% ok.





I suppose it's possible that the LVDS or the other 2 ribbon cables could have an internal problem - either short or damage internally to the traces?
I will order a used LVDS cable so that I can hopefully swap it out and eliminate that cable as the issue at least. I'm not sure if the short CN3 and CN4 cables will be available but I'll have a look.

If it comes to re-balling the IC2500, or even fitting a replacement / new IC2500 (looks like it might be available from China) then without the correct equipment, I will have to find someone that can do that for me, providing the cost isn't prohibitive.

[Diah]

Re: LG55UB850V no picture or audio - flashing LED's help please?

if you are sure no need to replace ribbon or lvds
log in instart and see the version of URSA remain same 0xe865 ?
and go to PowerOn/Off status let see what failure did registered

[Scoff]

Re: LG55UB850V no picture or audio - flashing LED's help please?

I followed the guide on another forum regarding the WebOS firmware and successfully managed to flash an older firmware onto the TV. I factory reset the TV afterwards but still the same problem remains.
I then upgraded to the latest firmware, which was the version running on here up until now, and again factory reset afterwards, however still exactly the same problem remains. So hopefully ruled out a firmware issue at least...

[Scoff]

Re: LG55UB850V no picture or audio - flashing LED's help please?

if you are sure no need to replace ribbon or lvds
log in instart and see the version of URSA remain same 0xe865 ?
and go to PowerOn/Off status let see what failure did registered

With instart the version of URSA does indeed remain 0xe865.
In the power on/off status menu, there are what would appear to be the most recent 125 entries for power on/off - it feels like a lot more LOL. These will all be from during the troubleshooting, so probably don't go back as far as the original power cut, if that's what you were getting at?

[Diah]

Re: LG55UB850V no picture or audio - flashing LED's help please?

the purpose we want to know why at that time didn't power on.. so the log will tell.

instop after update better than factory reset.

EDIT: if you explain to the reader of this threat how you managed downgrade to be usefull for them.

about the optical.. you may have under setting disabled it as source output for audio,,

[Scoff]

Re: LG55UB850V no picture or audio - flashing LED's help please?



We have Optical audio working again! Thanks for the suggestion Diah - I feel completely stupid now. I don't remember ever having to set the Optical Audio output, but then it's been years since I first setup the TV and never really touched it since! The first In_STOP must have reset this back at the start of the troubleshooting without me realising, and then when I was able to see the screen again I didn't think about checking the audio settings menu

OK so it feels nice to at least make some progress and fix something!!

In terms of the IN_START menu and power on/off history, there are no timestamps next to the various power on/off entries, so I don't know if any of them even go back as far as when the TV wasn't turning on - oldest page



Most recent page:

[Scoff]

Re: LG55UB850V no picture or audio - flashing LED's help please?

In terms of installing older firmware, I used the resources and information found here:

https://www.avsforum.com/threads/gui...-only.3217168/

[Diah]

Re: LG55UB850V no picture or audio - flashing LED's help please?

log 12 13 102 !!!
questiones when you downgrade did you checked by chance if MICOM Version changed or remain at 3.00.3

if not then downgrade then INSTOP . set the set then INSTART to check

[Diah]

Re: LG55UB850V no picture or audio - flashing LED's help please?

for explanation why i asked for downgrade.. the downgrade not just lower firmware version.. the important at this set case we need to have MICOM version different and BOOT version different if we downgrade and the BOOT or MICOM are same version the download software of the TV will ignore those section and will not over write. or rewrite.

but if they are downgrade to low we will be sure 100% the BOOT and MICOM rewritten to close suspect of SW.

[Scoff]

Re: LG55UB850V no picture or audio - flashing LED's help please?

I will have a look at the older firmware again and see what MICOM version installs when I re-install it.

In the meantime, I ordered a replacement LVDS cable to try, as it was cheap, just in case my cable had an an internal fault/short somewhere.
No change at all - replacement LVDS cable in place and still same behaviour, so hopefully rules that out at least.



I did come across a 'similar' problem in a thread here:

https://alpengeist-tvrepair.blogspot...connector.html

but not a good outcome!

[Diah]

Re: LG55UB850V no picture or audio - flashing LED's help please?

i would like to advice you. don't jump between internet cases.. you could lost and also could cause more issue. trouble shooting always considered as step by step to know what happen and where it happen.

we are focusing on your heat treatment which caused this... also it could be you did damage to the rand of panel because you put it on bed. who knows could small coin went between the panel and the bezel. so need to remove bezel and check the panel rand.

on the area effected by heating and related to T-CON circuit 12C_SCL and SDA.

LVDS cable should be disconnected . compare with diode mode Q 13004 & Q13005 (2N7002A)
also measure the 0 ohm R and 4.7K R

[Scoff]

Re: LG55UB850V no picture or audio - flashing LED's help please?

When you say 'rand' of panel, can I ask you to explain what you mean please as I don't understand the term?

I continued to install older and older firmware, to try to find one that uses a different MICOM version that 3.00.3 as per the latest firmware 05.05.90

I tried several versions, even going back to the original firmware version for this model, and they all use the same MICOM version. The Boot version did change though, if that makes any difference.






Performed IN_STOP reset after each firmware installation, but none made any difference to the screen and buzzing problem. I found one screen menu which highlights the screen problem very clearly:

https://photos.app.goo.gl/ZAjkg9gSuoqAnZ667

I have also tested the transistors on the MB as requested, although measurements are with this components still in circuit, so I don't know how helpful they are:

Transistor Q13005
- probe Gate, + probe Drain = 2.152
+ probe Gate, - probe Drain = 2.666

- probe Gate, + probe Source = 2.359
+ probe Gate, - probe Source =2.666

- probe Drain, + probe Source =0.618
+ probe Drain, - probe Source =1.625

Transistor Q13004
- probe Gate, + probe Drain = 2.158
+ probe Gate, - probe Drain = 2.666

- probe Gate, + probe Source = 2.364
+ probe Gate, - probe Source =2.666

- probe Drain, + probe Source =0.621
+ probe Drain, - probe Source =1.627


Resistor R13062 = 0.8 Ohms
Resistor R13061 = 0.8 Ohms
Resistor R13013 = 0.7 Ohms
Resistor R13014 = 5.775MOhms? This is supposed to only be 4.7 KOhms
Resistor R13019 = 5.775MOhms? This is supposed to only be 4.7 KOhms

[Diah]

Re: LG55UB850V no picture or audio - flashing LED's help please?

MOSFET Q13004 &5 reading fine as the diode between D & S intact.

bezel frame of the TV protect the area of the panel from 4 sides. this what i mean.

nothing remain in my head. if you didn't touch T-CON and some how static electricity damage it... stay only only Could COULD BGA issue in DDR.
i read you have flux .. so need to mask all parts from top side and down side around the first and second DDR where you did align the caps before.. put flux under the chip and with cold air pressure try to push it deep under the chip then apply heating.

[Diah]

Re: LG55UB850V no picture or audio - flashing LED's help please?

Resistor R13014 = 5.775MOhms? This is supposed to only be 4.7 KOhms
Resistor R13019 = 5.775MOhms? This is supposed to only be 4.7 KOhms

R13018 not (13014) & R13019 = 4.7K

don't forget LVDS should disconnected ..check again pls. you may blowing them out because of the hot air LOL

[Scoff]

Re: LG55UB850V no picture or audio - flashing LED's help please?

LVDS was disconnected during testing. I double checked with the magnifying glass, and it turns out that both R13018 and R13019 are actually empty - just pads with solder on, the same as a lot of other R numbers on the board.




This is obviously different to the service manual as seen in your picture of the circuit. Perhaps certain revisions to the board and this particular one doesn't have those 2 resistors?

The freeze spray arrived today so I will attempt this to see if I can alter the behaviour at all, as per your previous suggestion. Are the DDR chips ok to be frozen one at a time, or only the main IC chip - IC2500?

If no difference can be detected, I will move onto the heating of the DDR with flux as you also suggested.

EDIT: Just done some more reading and it seems these R13018 and R13019 resistors could be 'embedded' resistors within the PCB - is that correct? If so, my readings stand as above, although slightly higher when checking today, just over 6 Mega Ohms each.

[Diah]

Re: LG55UB850V no picture or audio - flashing LED's help please?

hold on.. dont do any further steps unless we clear the condition of R13018 / 19

they are not OPT on service manual.. and they are the feed of V to source. how it come they dont put them..
turn on the tv normal and read the any pins on those empty R one should 3.3V so about the other pins

[Diah]

Re: LG55UB850V no picture or audio - flashing LED's help please?

PHOTO so the service manual says .. yours Panel ( Module ) NON D9_12C (this why you have R13012 / R13013 0 Ohm connected to R13019 /R13018 4.7K ) and there are NO R13014 / R13017 0 Ohm )

also because yours Panel ( Module ) not a AUO brand so you don't have R13061 /R13062 0 Ohm )
so my mind tell me as S.M there are R13018 / R13019 .

[Scoff]

Re: LG55UB850V no picture or audio - flashing LED's help please?

Yes so R13012 and R13013 0 Ohms are both present and surface mounted R as per the service manual, so my module must be NON_D9_I2C like you say.

My module DOES have R13061 /R13062 0 Ohms present as surface mount R, as you can see form my last photo. So yes it is a Non-AUO Module.

I agree, there should be surface mount R for R13018 and R13019. Very strange...

I have turned the set on and tested both sides of R13018 and R13019. I get a different voltage reading from either side of each 'resistor'.
I have uploaded a picture to illustrate:

Red arrow side of R13018 and R13019 = 3.272v STABLE
Yellow arrow side of R13018 and R13019 = Fluctuates in time with buzzing, between 3.299v and 3.304v. During each 2 second 'buzz' the voltage climbs from 3.299 up to 3.304v, and when the buzz stops, the voltage falls back down to 3.299v.

[Diah]

Re: LG55UB850V no picture or audio - flashing LED's help please?

i do know yours Module non D9 and non AUO as yours LG Module 120Hz.

there are some things you did before you came here and posted the issue.. !!!! used heating maybe ... you have to asmit LOL

EDIt: try this... feed it with source signal and go to setting menu 3D be sure it turn off. or turn it on and then off and see if there any change.

[Scoff]

Re: LG55UB850V no picture or audio - flashing LED's help please?

OK I will try that and report back.

And no, I am not hiding anything, there is nothing to admit. I did NOTHING to the set before asking for help on this site!