My screen was leaking really bad on my Dell 7995 laptop. So I removed it I disconnected the LCD plug from the motherboard…as well as the camera, microphone and WiFi adapter. I have an external 27” monitor that I was going to keep connected through HDMI. i finished everything and it won’t power up. I later read that you need to keep the internal connection in tact or it won’t fire up. Is this true? It must have to recognize the video signal to power up? Thank you for any input. Joe