Why is my screen black?

I just repaired one of these under warranty. LG sent a replacement panel. (the panel today was called the picture tube back in the day). The power supply, Main board and T-con board from the original TV were place into the new panel. What has happened, the led lights are not coming on. Thanks for asking, Matt of Martins TV.

John Pantera first please verify your TV's exact model. Before replacing a panel you want to check a few things. Unplug your TV and remove the back. Then take a look at all the boards. Check for obvious damaged components like leaking or domed looking capacitors. Check to ensure that all the wires are properly connected. Once you checked that, take some good pictures of your boards and post those with your question. Use this guide iFixitでの質問に画像を追加する方法 for that. It will allow us to see what you see. This could be an issue with the power board not supplying the voltage for your backlight, your T-con board having failed or your backlight array. You will need a multimeter to check the proper voltages so let us know what you find thus far.