Replaced DC in port, now it powers on but blank screen

After I replaced the DC in port, I plugged it in and turned the power on. I heard all the usual/normal sounds of startup, but the screen remained blank. Caps lights up, so it is getting power.

I continued turning the mac on and off, and one time a white screen came up instructing me to type "re-boot" then press enter, or type "Shut-down" and press enter. When I typed "re-boot", something else popped up and there was some error that wouldn't allow for reboot (I forget exactly what it said). So I typed "shut-down," and now it won't go back the that screen or re-boot.

So clearly the LCD screen works, I just can't get it to come on.

any suggestions???

thanks,

Tom