kenwood head unit will not work

I just perchased a truck and the kenwood head unit in it will not work. I took it out. I know it has a security code on it because I have the code but cannot get it to power on. I have hooked the unit directly to the battery the constant and the switched a long with ground and nothing not even the security light when the face is off. The fuse in the back looks fine. Just in case and pulled a fuse that I knew worked and put it in there and nothing. Any other ideas? Please Help. 

Could be cold solder joints on the plug, open and check.

What is the model number of the Kenwood?