Toshiba Satellite S75D-A7272 screen black

My laptop got wet and wasn't tuing on whatsoever, so I replaced the motherboard. It now tus on, but the screen is black.

I've tried doing a cmos reset (holding the power button for 60 seconds while the battery and charger are unplugged). I did this at least 5 times with no luck.

I also tried plugging in an exteal monitor and TV using the VGA and HDMI ports. I tried pressing f4 and f5 to see if it would activate the exteal screens. Nothing.

Lastly, I tried switching out the ram.. nothing.

There is not even a dim screen... it's pure black, so caot be the backlight.

Do you think the motherboard's graphics card is faulty? Could it be the LCD inverter or the LCD screen itself?