Problem - Blackscreen after display assembly replacement

Hi, just replaced the display assembly on my mac and currently have a black screen.

I think i may have damaged the thin piece of foil on top of the inverter but i am unsure if this would cause the screen to be black.

The replacement display is brand new and i am only replacing it because the previous screen got smashed.

The screen has flashed once or twice but apart from that it has been black and the apple logo on the back unlit.

The chime still happens when i switch it on but the button backlights are sometimes on/sometimes off.

The only other thing worth mentioning is that i had tried to replace the ram cards with a suitable upgrade but was unsure if this could cause problems so reverted back to the original cards.

Thanks for any advice provided!