With the TV on. shine a flashlite in the screen to see if there is a picture. If not then the T-con board is bad. If you do see a picture the ballast board is bad. Some ballasts are incorporated into the power supply boards, others are on a separate board. If your TV back light are leds, then the driver most likely is part of the main board. You can go to this website for parts. You can call them, too so you'll be able to advice and the correct parts They have diagnostic and repair videos there too. www.shopjimmy.com