With power connected to the TV there should be 3.3V DC on pin 5 of the connector, lower right side of the power board as shown in your image.
Everything looks OK on the board i.e. no obvious damage and since you said that the main fuse is OK, without a schematic it will difficult as you would have to start checking if there are any voltages appearing on the "secondary" side of the board to know if the problem is on that side of the board or the high voltage primary side.
There is a "Power On" pin mentioned on the board (same connector as the Stand by pin) but this is only to turn the power board fully on once the mainboard gets the signal to turn it on from the remote or power button. So there should be no other voltages on the connector on the secondary side except the 3.3V which is supplied to the mainboard.
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