Black screen after RAM and screen hinge replacement

Hi guys

So I just replaced my MacBook hinge and also replaced new RAM.

But when I turn it on, there is just black screen. The MacBook itself is running (start and chime sound) but the screen is dead (no Apple logo light as well)

As far as I can see, I was very careful in replacing born the screen hinge and the ram. But I guess anything can go wrong.

I tried all the usual troubleshooting as mentioned else where here but no luck ..( Starting with ctrl, alt, shift, p, r.. etc)

I also tried replacing the old ram back again but still blank screen.

Any help would be appreciated.

P.s No Genius Bar appointments in the nearby store until next week and I will have to try to fix this by tomorrow.

Thanks