LG 47 LM8600 - No Video

[anupkg1985]

Re: LG 47 LM8600 - No Video

Yes all caps are reading 12 ohm except one just below L103 (not sure about the number, could be C336) is not showing 12 ohm. Below are the reading on 8pin ICs -

Ribbon connected / Ribbon disconnected
IC302 Vin 0.8M Lx 12 ohm / Vin 0.8M Lx 12 ohm
IC300 Vin 0.86M Sw 44K / Vin 0.87M Sw 44.5K
IC303 Vin 0.86M Sw 37K / Vin 0.87M Sw 37.4K

[anupkg1985]

Re: LG 47 LM8600 - No Video

Yes all caps are reading 12 ohm except one just below L103 (not sure about the number, could be C336) is not showing 12 ohm. Below are the reading on 8pin ICs -

Ribbon connected / Ribbon disconnected
IC302- Vin 0.8M Lx 12 ohm / Vin 0.8M Lx 12 ohm
IC300- Vin 0.86M Sw 44K / Vin 0.87M Sw 44.5K
IC303- Vin 0.86M Sw 37K / Vin 0.87M Sw 37.4K

[Diah]

Re: LG 47 LM8600 - No Video

My Post #15 point C. you are just diving at parts of T-CON had other function.. so first need to know yours panel where and how it work..
Yours Panel & Its T-con used not only as Normal 3D TV. but its ability of its Hz used also at Close Video Displaying System as Panel Info at airports/Stations/Terminal Gate etc. which the system work on NON LVDS Signal.. but 12C /SP controlled by UART hex command.

[anupkg1985]

Re: LG 47 LM8600 - No Video

My Post #15 point C. you are just diving at parts of T-CON had other function.. so first need to know yours panel where and how it work..
Yours Panel & Its T-con used not only as Normal 3D TV. but its ability of its Hz used also at Close Video Displaying System as Panel Info at airports/Stations/Terminal Gate etc. which the system work on NON LVDS Signal.. but 12C /SP controlled by UART hex command.

Thanks for the clarification on that. As per your post#15 point 1, what voltages do you expect on pin 43 to 48? As I noticed on the main board, pin 42 to 46 are connected to GND, pin 47 is N/C (not connected) and pin 48 to 51 are connected to 11 V.

[budm]

Re: LG 47 LM8600 - No Video

Yes all caps are reading 12 ohm except one just below L103 (not sure about the number, could be C336) is not showing 12 ohm. Below are the reading on 8pin ICs -

Ribbon connected / Ribbon disconnected
IC302- Vin 0.8M Lx 12 ohm / Vin 0.8M Lx 12 ohm
IC300- Vin 0.86M Sw 44K / Vin 0.87M Sw 44.5K
IC303- Vin 0.86M Sw 37K / Vin 0.87M Sw 37.4K

As you can see, the 3 buck converters, one has very low Ohms reading on the output pin compared to other output pin of other 2 buck converters.
If you look at the schematics of the IC302, you need to trace out the LX pin which goes to the inductor, and then you will have filter caps connected to the other ends of inductor, so it can be bad MLCC or the loads that are connected to the output inductor is bad.

[anupkg1985]

Re: LG 47 LM8600 - No Video

I see that pin 7 and 8 are connected to Rx pin of the IC302 which then connects to inductor L302. I could see the caps C131, C329, C332 are connected to other end of inductor, which reads 12 ohm. Also I could see there is one inductor L103 connected in parallel, could that be a reason to show low reading on those caps?

[budm]

Re: LG 47 LM8600 - No Video

So right now if you do not have LCD panel connected to the T-CON board, what DC Voltage do you have on the caps that show 12 Ohms readings.

[Diah]

Re: LG 47 LM8600 - No Video

Thanks for the clarification on that. As per your post#15 point 1, what voltages do you expect on pin 43 to 48? As I noticed on the main board, pin 42 to 46 are connected to GND, pin 47 is N/C (not connected) and pin 48 to 51 are connected to 11 V.

Not Much as want to know the LVDS signal 12V supply and you have it on 48-51 as you wrote.

[anupkg1985]

Re: LG 47 LM8600 - No Video

So right now if you do not have LCD panel connected to the T-CON board, what DC Voltage do you have on the caps that show 12 Ohms readings.

I'm getting 1.03V on those caps, panel disconnected.

[budm]

Re: LG 47 LM8600 - No Video

I'm getting 1.03V on those caps, panel disconnected.

What is the Vin feeding that IC?

[anupkg1985]

Re: LG 47 LM8600 - No Video

What is the Vin feeding that IC?

It's 11.65V on Vin (pin2) on IC302.

[budm]

Re: LG 47 LM8600 - No Video

It may be setup as 1V Buck converter, you can verify if that is true or not by checking the feedback resistor network, see the R1 and R2 of the IC spec sheet and see the resistors value used in your board to set the output Voltage of this Buck converter, see page 6 of the spec sheet.

[anupkg1985]

Re: LG 47 LM8600 - No Video

It may be setup as 1V Buck converter, you can verify if that is true or not by checking the feedback resistor network, see the R1 and R2 of the IC spec sheet and see the resistors value used in your board to set the output Voltage of this Buck converter, see page 6 of the spec sheet.

Sorry I couldn't locate those resistors on the circuit. Could you help to locate?

[Davi.p]

Re: LG 47 LM8600 - No Video

my opinion: the measurement on that caps are normal, that is the common dc-dc for the cpu vcore that has an high consumption then low ohm reading, 12ohms never tells about a short, the lg recent displays are different from other ones, the half side connect test never reveal an half good picture but vertical lines , there are many inductors on the tcon board, it must chek the voltage on every group of big mlcc near each inductor and report here, the voltages are common more or less so we can judge if good or not.

[budm]

Re: LG 47 LM8600 - No Video

I would check other Voltage outputs of other buck converters too to get some idea if they are working and putting out correct Voltages or not.

[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?

[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

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

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

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?