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Posted: Tue Dec 25, 2007 9:16 am
I seem to recall that in television sets, DC-coupled amplifiers were always so problematic that they were rarely used. So, especially in the older analog, all-discrete sets, they used AC-coupled amplifiers for the video and a DC restorer circuit to shift the black video level where it belonged.
Posted: Sun Jan 13, 2008 5:32 am
what about a diplexer of the type used for running a tv signal over the same cable as powered lnb's in satellite systems? there is a dc power passing i/o side and a dc blocking ac passing side and they are readily available from satellite dish installers, they use a standard 75 ohm connection for both i/o's and pass ntsc through the non power passing side. you can draw your dc from the other i/o.