Go to www.Shopjimmy.com
They have parts, videos, and test equipment for most brand flat screen TV/Monitors.
My LG 40" Television had the same symptoms.
No picture, but sound.
Did the flash light test, and that showed that the LCD was working.
In my case the LED Strips for the back lighting had burned out.
Thus, I ordered a replacement set of LED Strips from Shopjimmy.
Watched the disassembly video for my model TV.
Then when I got the parts in, I was able to do the repair within about 2-3 hours.
I needed to get some suction cups from Harbor Freight, for handling the LCD Screen.
Some Tar/Bug/Glue remover to get the sticky stuff off, where the old burned LED Strips had been attached.
So, I spent about $70 in total for the repair.
Terry Baker