Commodore 1702, no picture but audio is coming through fine

[Myxomatosis]

Hi there, first off sorry if this is posted in the wrong section I thought this would probably be the most appropriate one to post it in.

I just got a commodore 1701 and 1702 today for free, when I got back I hooked up my NES to the 1702. I have it hooked up to the a/v jacks in the front of the monitor, and the audio comes through fine, however there is no picture. Just to be thorough, I also hooked my SNES up in the same way, and the same thing (audio, but no video).

I couldn't really find anything online to see if this is an indication of it being completely broken or not, so I wanted to ask here. Does anyone here have any insight into this? Is it just broken?

Thanks for any help!