Video Bars on Plasma

[Talos4]

I have my Samsung SP-R4232 in the rec room.  

It is showing video bars ONLY on the Directivo input.

I have the STB hooked up using S-video. (best connection on this STB)

I noticed the bars immediately.

I installed a new 4X8 multiswitch last weekend replacing the rats nest of connections that previously existed.  

During that installation I forgot to hook up the ground blocks.  The bars were almost completely gone but not quite.  Hooked up the ground and they're back.

The 4 other STB's including the H-10 are completely clear of bars.

The only thing I can think of is that maybe the coax from the multiswitch to the STB may be inferior or damaged.

I'm using existing coax of unknown age that is run through the drywalled ceiling to the STB location.

OTA, DVD inputs are crystal clear.

Bad Coax, Bad Ground, :confused:  

Thanks

[tekdredger]

This sounds more like a ground loop than a poor ground.  You may want to try one of these to break the loop(s).