d900t/m7700 motherboard/screen issue

i bought a carillon/alienware/clevo d900t/m7700 latop which needed a new motherboard as the owner informed me..the laptop had no other issues....it sometimes would go to the bios screen and that was about it.......i have just purchased a new motherboard and installed it but to my surprise it wont even go to the bios once.....could it just be as simple as a wonky screen or something else???? the motherboad is fine and lights come on and fans kick in etc but nothing else
thanks for any help.

 

Double check your screen connection they can be really fiddly,undo the two side clips pull out the cable then push it in again firmly and clip the two side pins down again then retry,don't just do a visual inspection.

If this doesn't work connect an external monitor to see if you can get a post screen.

EDIT Buying laptop motherboards is a minefield,you should never buy them from private sellers as they are often already broken,stick to trusted Ebay business's who guarantee/test each motherboard and who accept returns without fuss.

If after you've double checked all your connections it doesn't start up I'd install the old motherboard again to see if it works as before,if it doesn't you may have broken something or missed a connection,if its does then take it apart again and reconnect the new motherboard if it still doesn't work you may want to seek a refund.