ColecoVision: Rolling diagonal lines

[rednakes1]

Just wondering anyone has any idea about this problem concerning a rolling interference pattern on my AV-modded Colecovision.

 

I'm attaching a photo to demonstrate what I am seeing on my CRT TV. It's a set of diagonal rolling lines on the screen that disappear after several seconds and then show up again. It drives me nuts, especially in games with a blue background (eg. The Coleco blue skill selection screen, or Evolution title screen).

 

This problem is most visible on my AV (composite) connection but also shows up on the RF coax input as well, though not as noticeable because the lower quality hides it a bit. I've tried the transistor AV mod as well as the op amp version of the mod, and neither rectified the issue.

 

I've also tried two different power supplies, cleaned the power switch and PCB, and tried different TV sets (CRT and LCD). I don't want to waste any more time on this but was just hoping someone can help out.

 

Someone else had this same problem a couple years back and he ended up selling the unit and buying another one, which didn't have the problem. So it wasn't an issue with his power socket or location.

Edited June 8, 2017 by rednakes1