The 1545 comes with a ccfl backlit screen with an inverter. I take it you've bought an LED backlit screen with a converter cable?
Make sure you've connected it as the suppliers instructions but it seems be be a bit of a lottery as to whether the led conversion works on your particular laptop model.
If I was you, if you cant get it working, I'd send it back and buy the original ccfl screen.
Hope you haven't damaged any circuitry in the meantime.