I've have a retail customer with a large TV display. The content they display is generated from a multimedia server with both an NTSC and ATSC outputs. The ATSC signal then feeds a high definition receiver which feeds a daisy chain of HD distribution amps. The NTSC signal feeds other TV's which are just used for general information.
The TV's are displaying a horizontal bar that moves from bottom to top very slowly. On the HD sets the bar is colored and on the analog sets it's just a dark bar.
Every componant has been changed out (server, video output card, amps, modulator, combiner, HD receiver, distribution amps and cables), and the bars are still there.
Even went as far as having a new server brought in and set it up right on the sales floor. The bars are still there!!!!! When I was feeding this from the back room the bars appeared in about 25% of the TV's, when I moved the server out on the floor, they appear in all of the TV's.
When I disconnect the HD receiver and connect a DVD player to the same HD distribution amps, the bars are gone!!!
At first I was trying to case this down as a ground loop problem, now I'm not sure. I'm thinking more like RF or EMI.
Store does have a ton electronics and some RF equipment (hand held scanners, two-way radios, etc). No transformers close by, electric room is 100' away.
Anyone have any ideas????