I picked up a colecovision, but when I hook it up I get no video, and a slight audio hum. The video doesn't change at all, I just get the fuzz from channel 4. The audio slightly changes when powered on.

I have basic soldering skill, but not sure what to tackle. I checked the power supply with another coleco and it works fine.

My question is, would the composite mod bypass this and fix the issue? If so, that might be easier than trying to desolder the Rf board and find the issue.

Any other thoughts on what to check?

Thanks