White power light comes on but black screen

White power light comes on but black screen

The power to my visio Eb600i-B3 won't come on.... I replaced the main power supply board twice but still nothing. I traced the current, which definitely comes in and travels all the way thru, the white light on the bottom comes on, but when I hit the switch the tv doesn't turn on. Does anyone know where the problem could be and what part I would need to order?

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