acer extensa 4620z screen replacement problems

So I have an acer extensa 4620z, I was replacing a cracked screen with a used screen that I know works after swapping out I booted it up and the screen is so dark you can barely see anything, now I swaped the cracked old one back in that worked fine just has half the screen blacked out because of a crack and it does the same thing, I can tell they are geting power and starting upbut its so dark I can't do anything with it and I tryd hitting the key combos to change brightness of screen from keyboard and nothing happens. Not really sure where to go from here or if I should just take it to a shop, I work with desktops so not to great with laptops. If anyone has any suggestions if you could post on here or throw me an email at [email protected] if need to text me or call if you know what to do I can give u my number through email. Thanks ahead!