Why doesn't it work?

Hi I have an RCA 39 inch LED LCD TV Model# LED39B45RQ. When I turn it on, nothing happens. The red power light goes off when powered on and nothing else happens. I do not have any audio or video. No illumination at all on the screen, totally black and dead. I measured all of the voltages and they are all good except the 24 volt back light LED supply is at about 50 volts both before powering on and after powering on. I have tried 2 new power supply boards and still the same problem. What other board or parts would cause this voltage to go to 50 volts. I have an electronics technician degree from Foothill College and used to be an electronic service technician at HP. I am also a Ham radio operator and am very familiar and knowledgeable in electronics. Without having a schematic to the TV, my guess would be that a voltage regulator has gone bad. Any ideas of what else would cause this problem besides the power supply board? Thank you, Roger Myers