Badcaps Forums

Badcaps Forums (https://www.badcaps.net/forum/index.php)
-   Troubleshooting TVs and Video Sources (https://www.badcaps.net/forum/forumdisplay.php?f=31)
-   -   LG 43UK6300 - Audio & Backlight, but no Video (https://www.badcaps.net/forum/showthread.php?t=82783)

arbitarytwist 02-19-2020 09:01 PM

LG 43UK6300 - Audio & Backlight, but no Video
 
7 Attachment(s)
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 02-20-2020 09:34 PM

Re: LG 43UK6300 - Audio & Backlight, but no Video
 
2 Attachment(s)
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 02-21-2020 01:31 AM

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 02-21-2020 09:31 AM

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

Originally Posted by budm (Post 943725)
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 02-22-2020 10:53 AM

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

Originally Posted by budm (Post 943725)
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 02-25-2020 11:01 PM

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 02-27-2020 02:36 PM

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 02-27-2020 08:53 PM

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

Originally Posted by sintv (Post 945135)
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.


All times are GMT -6. The time now is 11:36 PM.

Powered by vBulletin ®
Copyright ©2000 - 2020, Jelsoft Enterprises Ltd.