755CD Power Problem

[AlphaKilo470]

Hello folks, I have yet another ThinkPad to put in my collection. I just accquired a ThinkPad 755CD with all the manuals, software, a port replicator and a docking station. It has 24mb RAM and a 2gb HD. Problem is that the computer runs just fine off the battery alone, but when I plug in the power cord, nothing happens. I'm thinking that since the cord is good (tested w/ my 760) and the plug on the computer is not loose, it's my DC card or the motherboard. Am I right? I'm asking because I know I probably am (knowing my luck) but in one last shred of hope, I decided to post.

EDIT: Whenever I put the computer into the docing station, the docking station beeps over and over agian.