Model 2 Sonic the Fighters - wavy lines?

[SailorLodestar]

I’ve got this Sonic the Fighters board working again but it has these unpleasant vertical wavy lines that on screen. This seems to be a documented Model 2 experience as I’ve been able to find several posts about it but I haven’t been able to find a thread with a solution.

Does anyone here know what causes this? I don’t remember the game looking like this when I set it up almost a year ago.

 

[SailorLodestar]

I just found this post on a Reddit thread by someone who had the same problem with video from their NES and I wonder if they are related.

Theirs is an odd phenomenon that when I touch the volume pot of the jamma adapter while the game isn’t playing any sound, the cabinet speakers play sound from a local radio station. So I wonder if the video issues are due to radio interferrance.

I’m not sure if having the model 2 in a metal cage makes that better or worse.

 

[SailorLodestar]

A RAM test shows IC 18 as “bad”.