LG 60PK250N ZA No picture

[Fredrik_Bostrom]

Hi,

To start with I think I have red every single topic on this forum about the No picture fault on this TV. Seems like a common fault but I just can´t find a match i other forum threads for my TVs fault.

Symptoms:
No picture, not even a little primer.
Unable to check if I have sound since I don´t have any picture to navigate the menu to be sure I´m on the correct input.
When connecting power cable it clicks just like it used to and the red standby light on the front comes on.
When pressing the power button on the front it clicks like it´s supposed to and the standby light goes of. The screen stays completely black, no priming (or whats it called). The TV stays on, it doesn´t switch off.
When measuring Va, Vs and the 5v at the connectors on both Y-sus and Z-sus the voltage are correct so I guess the PSU is ok? Does this also mean that the Y-sus and Z-sus boards are ok?
I have tried disconnecting both Y-buffer boards, one at a time, but still no picture.
I have tried to bring up the "test screen" by detaching the main board from the control board and jumping the control board points but no test screen shows.

What I would like is some kind of logic troubleshooting schema where I can go from board to board and then the most common components to fail on each board according to my TVs symptoms and how to test/measure them, preferably in place. And what values to expect for at good and a faulty component.

Kind regards,
Fredrik

[nomoresonys]

Confirming, you did unhook both the control board and the powerboard from the mainboard when you did the test color pattern test?

[Fredrik_Bostrom]

Yes, I did. And just to be sure I did it once again just now and with the kids not running around making noice I can hear the tv going into test mode. It's like a cycle of different buzzing sounds from the sus boards which is only there when I put in the jumper for the pattern test. Without the jumper it's just a constant buzz. Still no picture or priming on the screen.

Please advise me what to try next.
I have used a IR thermometer to measure the heat sinks on the sus boards after letting it run for about 15 minutes. The temperature on some heat sinks gets raised by just 2 - 3 degrees Celsius while other get 10 - 15 degrees. I don't know if this info is usable.

Are there any components on the sus boards that are more prone to failure than others? And how do I measure them?

[tvtimmy]

Check the igbt's under the y-sus board for shorts. They are labeled with a "Q". It is strange that you have the correct voltages.

[lotas]

Предохранители живые?

[tvtimmy]

Lotas says to check the fuses he has circled.

[Fredrik_Bostrom]

Check the igbt's under the y-sus board for shorts. They are labeled with a "Q". It is strange that you have the correct voltages.

How can I check them when they are still attached to the board? Do I have to remove them to be able to test them?
I dont have a IGBT-checker, just a multimeter. Hon can I test them with my multimeter when they are still attached to the board?

[Fredrik_Bostrom]

Предохранители живые?

I tested them with a multimeter when they are still attached to the boards and they all read about 0,5 ohm.

[Fredrik_Bostrom]

Lotas says to check the fuses he has circled.

Thanks

[lotas]

If you can’t even check the fuse, then you won’t be able to repair a plasma TV, it’s very difficult to repair, it’s not an LCD TV. You can check the fuses without desoldering, at their terminals on the sides...

[Fredrik_Bostrom]

If you can’t even check the fuse, then you won’t be able to repair a plasma TV, it’s very difficult to repair, it’s not an LCD TV. You can check the fuses without desoldering, at their terminals on the sides...

Thank you for clarifying that.

[nomoresonys]

Common problems are like in this video, check powerboard for bad solder joints, and check both Y and X boards, check those solder joints as well, transistors go bad a lot as mentioned above and in the video, always make sure all screws are snug and ALL in place. A loose screw can short stuff out, you can test the buffer boards for shorts, plenty how to videos on youtube for that also: https://www.youtube.com/watch?v=VXnFYOfRdIk