Chosen Solution
I have an S7 with no display, it makes noise and you can hear the screen working when you tap it but there isn’t a single pixel lit up, I tried another motherboard on the same screen and its working fine so it isn’t the screen. So it’s something on the motherboard but what would it most likely be?
I would first check the LCD FPC connector on the motherboard. Look for broken, bent, burned, or corroded pins on the connector or loose/broken pads on the motherboard where the connector is soldered to. You might try posting a high-res photo of the board around the connector
