LG 47 LM8600 - No Video

[Diah]

Re: LG 47 LM8600 - No Video

Not sure but it's very confusing for newbie like me. I'm just concerned about the panel, if it's bad then there is no point to invest money in the t-con. Also I saw many videos of solving this issue by baking the main board in oven, do you think I should attempt that? I'm just concerned of damaging main board.

i do understand your worries and they are reasonable too because you dont know the history of the TV. also instate backing the MB. just use hot air gun to heat IC9300 after you recover all area around it to avoid SMT parts flying out by hot air.

[anupkg1985]

Re: LG 47 LM8600 - No Video

On some models a problem to the panel,, can cause the tcon software to set a flag in the eprom that switches off the tcon in protection, but in this case , now i note, the tensions are present so no eprom problem. Now have to test if signals come to tcon, on the lvds rails at the eol resistrs 100 ohm, have to see a tension around 1,3v, if the rail that carries the sync signals is missing i think image is not displayed. This is somehow a rare defect i think. The option of mainboard cpu bad soldering is not impossibile, so a test on the lvds lines maybe can reveal cpu to tcon output.

I haven't done the test Diah suggested in above post with hot air gun however below are voltages I'm getting on the LVDS pins on mainboard -

PIN1 0.14V
PIN2 3.2V
PIN3 0.14V
PIN4-6 3.3V
PIN7-8 N/C
PIN9 3.2V
PIN10 N/C
PIN11-41 0V (most of them connected to IC9300 not sure if I can measure voltage on those?)
PIN42-46 GND 0V
PIN 47 N/C
PIN48-51 11.2V

[Davi.p]

Re: LG 47 LM8600 - No Video

To test the lvds lines in this design without external resistors you must test between the couples 12-13, 14-15 , 16-17, ....... 23-24, not from pins to ground..

[anupkg1985]

Re: LG 47 LM8600 - No Video

To test the lvds lines in this design without external resistors you must test between the couples 12-13, 14-15 , 16-17, ....... 23-24, not from pins to ground..

Tested in pairs, some of them has 0.12V and some of them are just 0V. Not sure if that's correct. Will try luck by heating IC9300 or else will go for tcon replacement.

[Davi.p]

Re: LG 47 LM8600 - No Video

Right said Fred...

[Davi.p]

Re: LG 47 LM8600 - No Video

Mmmmmh... i' m not on this advice.. i think if bga work did not work the next purchase must be mainboard... but not before making some poking around on the panel's boards searching for obvouus short circuits on caps.

[anupkg1985]

Re: LG 47 LM8600 - No Video

After long time today I thought of resuming work on this TV and guess what, it started displaying video as soon I plugged the power cable. Now I'm not sure what was the issue and how long it will work. Can some one throw some light on this, what could have happened?

[sigmeyer]

Re: LG 47 LM8600 - No Video

Could be a bad LVDS cable , you messing around with it probably reconnected some pins and now its working ... Maybe try messing with LVDS cable and see if problem happens again.

[anupkg1985]

Re: LG 47 LM8600 - No Video

Will try that. Looks good so far. Will update with findings.

[anupkg1985]

Re: LG 47 LM8600 - No Video

Hi,

TV worked for couple of months and again there is no video. I checked lvds cable and looks good. Not sure what is the issue? Any pointers?

[alfatv]

Re: LG 47 LM8600 - No Video

Can you get access to long boards attached to LCD? I think you need to remove metal cover(s).
Also disconnect cables from T-con one at the time and check if you see same behavior as before.