LG 47 LM8600 - No Video

[anupkg1985]

Re: LG 47 LM8600 - No Video

try all the previous voltages with panel connected.

There is no change in voltages after connecting panel, still no picture or osd menu.

[Davi.p]

Re: LG 47 LM8600 - No Video

try all the previous voltages with panel connected.

[anupkg1985]

Re: LG 47 LM8600 - No Video

Yes, the tcon is defenately outputting the right tensions i guess, so no problem with it, even if i don't know what it means and don't think changes some, connect all things , turn on tv and push the tcon button, let see what happens, if nothing i guess there's a problem on the panel, also try all the previous voltages with panel connected. Have you got an eprom programmer?

No I don't have eprom programmer bu can arrange it. What is the further test? Do you think it's worth of giving try with new t-con board or more likely panel it self is bad?

[Davi.p]

Re: LG 47 LM8600 - No Video

Yes, the tcon is defenately outputting the right tensions i guess, so no problem with it, even if i don't know what it means and don't think changes some, connect all things , turn on tv and push the tcon button, let see what happens, if nothing i guess there's a problem on the panel, also try all the previous voltages with panel connected. Have you got an eprom programmer?

[anupkg1985]

Re: LG 47 LM8600 - No Video

I guess 12v is ok, have you found the missng Vgate high and Vgate low? 27v/ -6v..

I could measure 27.7V on C528 and -4.9V on C538 caps, not sure if thats what we are looking for?

[Davi.p]

Re: LG 47 LM8600 - No Video

I guess 12v is ok, have you found the missng Vgate high and Vgate low? 27v/ -6v..

[anupkg1985]

Re: LG 47 LM8600 - No Video

It seems a bit low, maybe you can test the 12v on psu with a dummy load? Or does you feel heat on the tcon chips?

I'm getting 11.89V on PSU when mainboard connected. There is little heat on t-con chips but I believe it's normal operation.

[Davi.p]

Re: LG 47 LM8600 - No Video

It seems a bit low, maybe you can test the 12v on psu with a dummy load? Or does you feel heat on the tcon chips?

[anupkg1985]

Re: LG 47 LM8600 - No Video

for the L505 i see also a slight low imput voltage of 11,2 when it have to be 12v, can you test the input v at the fuse?

I'm not able to locate the fuse on the board, however I checked the voltage on each pin of LVDS and max I could get is 11.46V from main board.

[Davi.p]

Re: LG 47 LM8600 - No Video

for the L505 i see also a slight low imput voltage of 11,2 when it have to be 12v, can you test the input v at the fuse?

[anupkg1985]

Re: LG 47 LM8600 - No Video

https://www.badcaps.net/forum/attach...0&d=1606335986
There are 4 more switching power supplies, you can see inductors with220 and 6R8 markings, that you need to check. There should be power supply that produce the AVDD boosted Voltage and also minus power supply for VGL, to bad they do not provide marking for Voltage test points.

Yes I have tested those, could you please find the reading in comment#40. There is a 16.43V on L506 inductor.

[budm]

Re: LG 47 LM8600 - No Video

https://www.badcaps.net/forum/attach...0&d=1606335986
There are 4 more switching power supplies, you can see inductors with220 and 6R8 markings, that you need to check. There should be power supply that produce the AVDD boosted Voltage and also minus power supply for VGL, to bad they do not provide marking for Voltage test points.

[Davi.p]

Re: LG 47 LM8600 - No Video

That 8 v feels out of place for me, let me think..

[anupkg1985]

Re: LG 47 LM8600 - No Video

test C512 , C508 near L505, rectify, L505 maybe is a stepup.
check akso if the micriswitch pins are connected to eprom (the one with yellow paint spot)

I can read 8.2V on C512 and 11.2V on C508. Also pins 1-4 are connected to GND of that microswitch and 3.2V present on pins 5-8.

[Davi.p]

Re: LG 47 LM8600 - No Video

test C512 , C508 near L505, rectify, L505 maybe is a stepup.
check akso if the micriswitch pins are connected to eprom (the one with yellow paint spot)

[anupkg1985]

Re: LG 47 LM8600 - No Video

i think you measure wrong, there are 7 inductors so 7 tensions, L506 is a stepup so in the group of 5 caps you must find a tension over than 12v, L505 is step down so on C512 you have less than 12v, L502 is step down and you find less than 12v, L301 is stepdown so less than 12v in C314, L304-L305-L306 are stepdown so less than 12v. Test also C500, C 505, and since i can't identifily the stage for the Vgate high test every single "big" cap for a tension about 27v, you must also find a -6v approx.

Here are the readings -
L506 16.43v
L505 8.22V
L502 3.2V
L301 1.53V
L304 1.03V
L305 3.2V
L300 1.79V

C500 1.01V
C505 1.7V

Not sure where to test Vgate voltage?

[Davi.p]

Re: LG 47 LM8600 - No Video

there are 7 inductors so 7 tensions, L506 is a stepup so in the group of 5 caps you must find a tension over than 12v, L505 is step down so on C512 you have less than 12v, L502 is step down and you find less than 12v, L301 is stepdown so less than 12v in C314, L304-L305-L306 are stepdown so less than 12v. Test also C500, C 505, and since i can't identifily the stage for the Vgate high test every single "big" cap for a tension about 27v, you must also find a -6v approx.

[anupkg1985]

Re: LG 47 LM8600 - No Video

every inductor is for a dc-dc stage, near the inductor some caps of a certain dimension, not the smaller ones, test on those caps. Mark only the tensions you find, not the place. The tensions you marked are surely good.

I'm getting 1.7V, 1.03V and 3.2V on the big caps around those inductors.

[Davi.p]

Re: LG 47 LM8600 - No Video

every inductor is for a dc-dc stage, near the inductor some caps of a certain dimension, not the smaller ones, test on those caps. Mark only the tensions you find, not the place. The tensions you marked are surely good.

[anupkg1985]

Re: LG 47 LM8600 - No Video

Below are the Vout on other IC and similar I could measure on the mlcc around those ICs.

IC302 1.03V
IC303 3.3V
IC300 1.8V

Also I could measure voltage on each mlcc on the tcon board. Not sure if tcon is good and issue with main board?