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Hi and welcome to JustAnswer,Thank you for the question and your patience. Should you still need assistance for information purposes only...Initially, if the Magnavox 46ME313V/F7 is completely/electrically dead, then it would still be a power supply issue.
On the otherhand, if it has some indication of power such as a blinking LED light, then it would have kicked in auto protect mode.
Considering that "...have changed the power and the main and still nothing...", then suspect the LED array at the LCD panel ass'y powered by the LED driver circuit of the power supply board. Temporarily disconnect the LED array and test run to determine if there would now be sound and/or a ghost screen image of the MENU with the help of a flashlight.