Here is another suggestion. If changing the monitor's contrast control while
it's running affects the interference, then it is coming from the monitor. If
not, then it is coming from the card, OR the video cable.
I once troubleshot a horrible video problem with my brother's professional CAD
station. He worked from home. Despite a shielded monitor with over a hundred
screws in the shielded box, it was knocking out TV reception in the apartments
next to his on all six sides. I tracked it down to improper shield
terminations in the video cable. We were able to add another shield over the
video cable, properly terminated, that solved the probem.
I saw a similar problem with a cable shipped by a company selling TV cards for
computers. Their card connected the TV video in a "T" fashion, and since they
had put pigtails over an inch long on all the shields, those shields radiated
video signals when we evaluated the card with our computer, with the TV card
not selected. Now the interesting part: The TV card _had an FCC ID_. It had
apparently been tested ONLY in operational mode. Adding a poor quality video
cable made the system in which it was installed radiate, and at non-compliant
levels.
Cortland
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