This model has a common screen failure that causes the LED backlights to not turn on. One method to isolate the screen and test for this is to disconnect both the LVDS cables going to the screen and then turn on the TV. If the backlights come on now and they didn't before then the screen is the culprit and no board replacement will correct this.
 
IMPORTANT: If you experience WiFi issues after replacing the main board please perform the "Reset Network" function which can be found under the menu option General / Network
 
 
Part Number:
BN94-12640X


Board Number:
BN94-12640X| BN97-13635A| BN41-02568B

model list:

Samsung   
UN40MU6290FXZA    FB02,FA01
UN40MU6290FXZC   

ap-4