LG 47 LM8600 - No Video

[anupkg1985]

Hi,

I have got a LG 3D tv with model LM8600. It has no video however can hear audio when connected the source. All the voltages on PSU are present like 3.5/12/24V. I could see backlight is working properly. Also I could measure 16.42V across the caps on TCON as marked in the picture. I suspect the bad t-con however not sure. Can somebody tell me what's going wrong with this set?

[Nick's Tvs]

Re: LG 47 LM8600 - No Video

Since you are able to hear audio, there is a chance your panel is bad.
Disconnect half of the screen by disconnecting one of the two ribbons which connect the T-con board to the panel and power it on. If you see picture on the half still connected then then it confirms a bad panel and we can deal with it from there. If no picture appears, reconnect the disconnected ribbon and disconnect the other and power it back on. If still no picture appears then you could have a main board or T-con problem. Most likely your main board is defective if the panel is not the fault and is not sending proper signals to the T-con and in turn not sending signals to the panel.
Use hot air or a blow dryer and heat up the large heatsink in the center of the main board while it's disconnected from power then power it back on and see if that allows it to work temporarily. If it does then indeed our main board is the issue. If not, then you could have a T-con issue.

None of this is very scientific or very accurate, however 75% of the time it will allow you to identify the source of the problem quickly without having to bust out a buch of tools and equipment you may not have on hand.

Let us know of your results and we can proceed from there.

[Diah]

Re: LG 47 LM8600 - No Video

Hi,

I have got a LG 3D tv with model LM8600. It has no video however can hear audio when connected the source. All the voltages on PSU are present like 3.5/12/24V. I could see backlight is working properly. Also I could measure 16.42V across the caps on TCON as marked in the picture. I suspect the bad t-con however not sure. Can somebody tell me what's going wrong with this set?

this is wrong points to make measurements on T-CON. you could toasted the T-CON self or one of COFs of panel. because any load you ad with yours DM there will be increase of mA feed to the panel.
you should only test the F1 fuse close to LVDS sockets on T-CON if there 12V. on both side of the F1.

beside the test suggested above.....
you have on T-CON SPI ( Flash eeprom ) RESET Micro switch. press it and keep pressing while you plug in the SET at wall sockets. give attention to your screen at this moment.

[anupkg1985]

Re: LG 47 LM8600 - No Video

Thanks Nick and Diah for replying on this. I did the test by removing ribbons from t-con to panel and looks like issue is with panel as I could see half white however no picture. Please find the attached photos. Let me know if this can be repaired or this set is done with its life.

[anupkg1985]

Re: LG 47 LM8600 - No Video

Also I could measure some of the smd caps are shorted. Does this cause an issue?

[Diah]

Re: LG 47 LM8600 - No Video

YES.
usually only one could be shorted

[anupkg1985]

Re: LG 47 LM8600 - No Video

How about the panel? Does that an issue 🤔 too?

[Diah]

Re: LG 47 LM8600 - No Video

How about the panel? Does that an issue 🤔 too?

???

did you done the ribbon cable disconnecting one at time with video signal? it should with video signal and you can hear sound.

the smd cabs you talked about shorted are they on the edge boards of the panel ??

always show photos will be better

[anupkg1985]

Re: LG 47 LM8600 - No Video

???

did you done the ribbon cable disconnecting one at time with video signal? it should with video signal and you can hear sound.

the smd cabs you talked about shorted are they on the edge boards of the panel ??

always show photos will be better

Posted observations in comment #4. I'll attach the photos with shorted caps, however those are not on panel edge.

[anupkg1985]

Re: LG 47 LM8600 - No Video

All the caps marked in red area are showing shorted, could be one or more are bad among them.

[Diah]

Re: LG 47 LM8600 - No Video

i dont think they are shorted..
can you measure on the LVDS socket P600 from pin 43 to 49 did they have 12V ? black probe tv chassis

[anupkg1985]

Re: LG 47 LM8600 - No Video

I'm getting 11.8V on pin 49 only. Nothing on other pins from 43 to 48.

[Diah]

Re: LG 47 LM8600 - No Video

please shoot close photo on this socket p600

[anupkg1985]

Re: LG 47 LM8600 - No Video

please shoot close photo on this socket p600

Attached snap of P600 connector.

[Diah]

Re: LG 47 LM8600 - No Video

okay thanks,
my judgment:
A- yours measurement at this post not correct

B- yours Panel OKAY. the line you saw after disconnecting right side ribbon cable are related to signal share at the panel self as it is 3D panel ( we understand how signal shared by side by side for example )

C: the SMD caps you mentioned are not shorted because they are related not direct to T-CON Normal operation.. ( they related to UART section for out source signal )

Issues: because you dont owned any further test and measurements instruments i will try to narrow the issue.
1- T-CON as you suspected .. but before you go for replacements make visual sight check to the panel edge boards and the glass too.. no need to test or touch.. just eyes sight enough.

2- if T-CON replacements didn't fixed it then the last OPTION BGA at Main boards...

3- as end from my side ..all up to you if you would like to start with points 1 or 2.

happy thanksgiving to all.

[budm]

Re: LG 47 LM8600 - No Video

All the caps marked in red area are showing shorted, could be one or more are bad among them.

What are the actual resistance readings on those caps that you say they are shorted? That is witching power supply. What is the P/N of that 8-pin device?

[anupkg1985]

Re: LG 47 LM8600 - No Video

What are the actual resistance readings on those caps that you say they are shorted? That is witching power supply. What is the P/N of that 8-pin device?

I read the resistance as 12.7 ohm on those caps. Sorry but not sure which 8 pin device you are referring to? Thanks for the attention on this.

[budm]

Re: LG 47 LM8600 - No Video

I read the resistance as 12.7 ohm on those caps. Sorry but not sure which 8 pin device you are referring to? Thanks for the attention on this.

12 Ohms in both directions when you switch the probes around?
IC302, as you can see, there are 3 switching power supplies in that section of the board, you can see 3 inductors, they are labeled with 3R6 3T on the top, and you can also see 3 8-pin IC next to each one of the inductor.

BTW, if you check those similar caps in the other 2 power supplies, do you get same low readings?

[anupkg1985]

Re: LG 47 LM8600 - No Video

Yes it's 12 ohm in both direction, however I don't get lower reading on other caps on other 2 power supplies. It's reading in range of 1K to 6K ohm on other caps. Part numbers for those power IC (direction from top to down) -

IC302 Z1038PI
IC303 54327 T1 22A
IC300 54327 T1 22A

[budm]

Re: LG 47 LM8600 - No Video

Yes it's 12 ohm in both direction, however I don't get lower reading on other caps on other 2 power supplies. It's reading in range of 1K to 6K ohm on other caps. Part numbers for those power IC (direction from top to down) -

IC302 Z1038PI = AOZ1038PI Buck converter
IC303 54327 T1 22A = TPS54327 Buck converter
IC300 54327 T1 22A

So are all the caps in that section show 12 Ohms?
IC302: You need to check the resistance (with and without ribbon cables between T-CON and LCD panel) between circuit ground and LX pin, circuit ground and Vin pin
IC300/303: Check the resistance between circuit ground and SW pin, circuit ground and Vin pin.
You do know how to read schematic, correct?

https://cdn.badcaps-static.com/pdfs/...a7eec30822.pdf