My Magnavox HD TV went out on my one day while watching it, had sound, but no picture. I did some googlinginging and found one test is if I shine a flashlight at an angle on the screen I should see the picture, sure enough I could. Turned out the inverter board is bad. No parts available anywhere. Welcome to the toss and replace world. Used to be you called a tv repair man and he would be able to come out and repair the set, today, you toss it in the trash and buy a new one since repairing the old one would cost more, IF you could find the parts.
Now I have a bigger set with more features for HALF of what I paid for the other one.