I have a model 1 genesis and whenever i put the cart in and press on two fuzzy bars go across the screen with artifacts of whatever should be on screen. (For example it says "produced by or" in giant letters but scattered across these two bars. Then when it usually turns to the "SEGA!!!!" screen the bars turn white.)

It should be noted that the system worked fine until I put a nes ac cord in it and left it there for awhile, I came back a week later and turned it on and this happened. Did I just destroy the system because of this (I'm using the official SEGA cord now)?