I wrote a few days back about my HDMI / HDCP problems. The follow-on problem was that the component video gave my scrolling horizontal bars on the screen.

I googled “component scrolling bars” and all things pointed to a ground-loop problem. A ground loop is where you have current flowing over ground between components; ground should be ground throughout, it follows that ground, being equal potential all around, should not have any current.

First I checked to make sure the socket was wired correctly — sure enough it was just fine.

Next I looked at the power strip. Only one plug even had a ground connection: the TV. The connection between the receiver was already digital and that didn’t exhibit a problem with other components so I could rule that one out. Only the TiVo had a problem.

?

I started looking around the back of the TiVo. The only other thing is the cable connection. I disconnected the cable and sure enough the bars went away.

I don’t have the schematics of the TiVo so I’m going to make some guesses here. The RF section of the cable interface shares a ground with the high-frequency driver of the component interface.

My power strip has a protector for the cable. I went down to the box of wires in the basement and picked up a jumper with a pair of F-connectors on each and and put that in the loop. My hope was that the ground from the power strip would also ground the shield of the cable.

The shield of the cable, in theory, is ground. But if it’s a noisy ground then it could cause this problem right here.

Sure enough with the power strip in mix the bars went away.

And there was much rejoicing!  :-D