This is an old post, preserved for reference.
The products and services mentioned within are no longer available.
I have done several TV Game composite video conversions recently, and they have all been pretty much the same, locate the composite video signal feeding into the modulator. Disconnect or remove that and fit a composite video buffer board to drive the TV.
black and white ones, and colour ones, this one is monochrome, with greyscale, but that should be the same, shouldn't it?
more on that in an earlier blog). Here, none of the signal goes near the black level, and the rest is small white peaks on grey.
I opened one up on a previous unit and found a 7808 regulator in there.