Model 4 No Text on Screen

I have a non-gate array model 4 which was supposedly working when shipped to me. The monitor works as the brightness and contrast work. When I put in a disk you can here the drive accessing the disk. Problem is no text shows on screen. I looked for the obvious to see if anything was disconnected such as the cable that goes from the mainboard to the video board but did not find anything that looked out of sort. Can you guys point me in a good direction to look?

Thank you in advance,


Brian