LG 47 LM8600 - No Video

[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.

[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.

[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?

[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

What is the Vin feeding that IC?

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

[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

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.

[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.

[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.

[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

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

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.

[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

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

[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

[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

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

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

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?