LG 43UK6300 - Audio & Backlight, but no Video

[arbitarytwist]

I have a LG 43UK6300BUB that has Audo and Backlight.

I am no TV expert, but have done some troubleshooting on TV's in the past.

When i turn the TV on, i can hear audio and the backlight turns on, but there is no picture. Most of the trouble shooting videos i have seen, have a seperate main and T-Con board, but it seems like on this unit, the T-CON and Main board are the same.

I have checked the voltages on the connector from the Power Supply and i seem to be getting 13V, 3V & 2V to the Main board. I tried disconnecting one panel cables at a time and still no video on either half of the TV.

I haven't found anything obvious, but was trying to check the voltage to the display, but don't see any test ports, so would appreciate some help in troubleshooting.

This TV is about 16 months old with a manufacture date of 08/2018.

I have attached some pictures for reference.

[arbitarytwist]

Re: LG 43UK6300 - Audio & Backlight, but no Video

OK did some more looking around and seems like a burnt Transistor. I wasn't that pronounced, as in the original pics i posted, but i figured i try the oven bake and it made it more obvious. The behavior is the same as before the bake in.

I have attached some closeup pics (before over bake as seen in Pic #2 in original post).

How would i go about finding what the transistor and perhaps replace it. The two resistors above it when measured are around 70 Ohm each although there is some discoloration on one of them perhaps from the burnt transistor.

The part # for this mother board is EBU64688103 and wondering if i use EBU64688102, will that work, or would that be a different firmware ?

The complete model # for this TV is 43UK6300BUB.

[budm]

Re: LG 43UK6300 - Audio & Backlight, but no Video

I would remove that Transistor and then check the resistance between Ground against all 3 empty pads of that Transistor to see if any one of them shows <50 Ohms.
If not then put the cables between the main board and the LCD panel back in place and recheck the resistance again to see what it shows on all 3 pads.
We want to make it is not short circuit in the LCD panel that causes the Transistor to burnt out.

[arbitarytwist]

Re: LG 43UK6300 - Audio & Backlight, but no Video

I would remove that Transistor and then check the resistance between Ground against all 3 empty pads of that Transistor to see if any one of them shows <50 Ohms.
If not then put the cables between the main board and the LCD panel back in place and recheck the resistance again to see what it shows on all 3 pads.
We want to make it is not short circuit in the LCD panel that causes the Transistor to burnt out.

So i took some measurements with panel cables disconnected to ground and am getting 30 KOhm, 50 KOhm and 80 Ohms on the emitter (leg by the R1104). With the panel cables hooked up, there isn't much change.

[arbitarytwist]

Re: LG 43UK6300 - Audio & Backlight, but no Video

I would remove that Transistor and then check the resistance between Ground against all 3 empty pads of that Transistor to see if any one of them shows <50 Ohms.
If not then put the cables between the main board and the LCD panel back in place and recheck the resistance again to see what it shows on all 3 pads.
We want to make it is not short circuit in the LCD panel that causes the Transistor to burnt out.

With the postage values do you concur there is no short ? How would I go about finding a replacement transistor. Can't find any part# on the old one.

Is there anything else I could do to be 100% sure it's not the panel.

[arbitarytwist]

Re: LG 43UK6300 - Audio & Backlight, but no Video

So i did a bit more digging and following are the voltage readings i got

OFF (V) ON (V)
B 7.8V 10.5V
E 7.8V 13 V
C 0V 0V (No Transistor in Place)

This makes me think its a PNP transistor. I am wondering what i can use as a transistor to make this work.

[sintv]

Re: LG 43UK6300 - Audio & Backlight, but no Video

Disconnect one of the screen cables and see what happens. Iv just scrapped a slightly older LG although it had a Tcon board. Symptom was no video but backlights and sound ok. When I removed one cable, picture came on half the screen.

[arbitarytwist]

Re: LG 43UK6300 - Audio & Backlight, but no Video

Disconnect one of the screen cables and see what happens. Iv just scrapped a slightly older LG although it had a Tcon board. Symptom was no video but backlights and sound ok. When I removed one cable, picture came on half the screen.

I tried that already. Makes no difference.

[Jay Son]

Re: LG 43UK6300 - Audio & Backlight, but no Video

Hello,

I have the same TV, I have the same problem.
I have sound, backlight, but no picture at all...I tried unplugging half the screen at a time as well, no change. I don't see anything physically wrong, how and where do I start?

[Hamie]

Re: LG 43UK6300 - Audio & Backlight, but no Video

Don't bake your motherboard would be the first bit of advice.

Take a picture of the tv with the back cover removed so we can see how it connects to the screen.

[Hamie]

Re: LG 43UK6300 - Audio & Backlight, but no Video

If your model doesn't use a tcon then the old method of unplugging half the screen may not work.

[Davi.p]

Re: LG 43UK6300 - Audio & Backlight, but no Video

There is always a tcon in a lcd, here it is integrated to the main board even if i see too few chips near the dc dc section, so i ask a photo of the back of the mainboard. Silkscreens must be readable..

[Jay Son]

Re: LG 43UK6300 - Audio & Backlight, but no Video

Lol, I would never place my electronics in the oven 😂

My Tcon is integrated into my main board

[Davi.p]

Re: LG 43UK6300 - Audio & Backlight, but no Video

It's incredibile, the tcon part is almost invisible, i'm wondering where electronics wants to go an can go, but this smells to me like more unreliability... anyway i guess the fault is tcon, time to search for testpoints and the same old tipical tensions, unfortunately i see no named testpoints so i must edit the picture but i'm at hospital , i can't for now... but maybe between some days or a week.. who knows?...

[sordids999]

Re: LG 43UK6300 - Audio & Backlight, but no Video

Did you manage to find the fault with this tv ?

[alfatv]

Re: LG 43UK6300 - Audio & Backlight, but no Video

I had similar problem, you can try scotch tape method. Obviously, burnt part needs to be replaced. Mainboards for these are cheap however.

[lcdrepair]

Re: LG 43UK6300 - Audio & Backlight, but no Video

I just fixed one of these exact sets. The tcon is tab bonded to the lcd panel. I pulled one side from the mainboard . Turned on and same problem. Reconnected ribbon pulled other side and got half screen working perfect other half white. I used tape method. Scotch tape Covered 6 pins starting from pin1 on the ribbon that causes whole screen to blank. The whole screen came up looking fine. Is trial and error covering the right pins. Something is obviously failed and tape has bypassed issue for now lets see how long it lasts.

[hopkok]

Re: LG 43UK6300 - Audio & Backlight, but no Video

Hi, I have two TVs 43UK6300 and both have the same problem (sound,backlight, no picture), I did not find anything burned under scope, so no guess is, panel fault.

[alfatv]

Re: LG 43UK6300 - Audio & Backlight, but no Video

Hi, I have two TVs 43UK6300 and both have the same problem (sound,backlight, no picture), I did not find anything burned under scope, so no guess is, panel fault.

Did you read posts 16 and 17?

[whatusername]

Re: LG 43UK6300 - Audio & Backlight, but no Video

Why would you stop reporting on this with so many people having the same issue and no resolve as of yet. I have a 49sk8000 same exact issue. I replaced the main board and it worked for about 2 hours then died again same issue as before. Since then I have tried 3 more boards and a set of lvds cables and I still have the blank screen with backlight and sound. Is it gonna be the panel? Tv isn't even 2 years old yet