DVD player to vintage color TV set, using a modulator and filters
 

First thing to do is to salvage the TV modulator from a dead
VCR. These will have an audio and a video input terminals, as
well as a supply terminal, likely 9 or 12V DC. And an output
that would feed a "TV/VCR" RF switch (a module with "ant in"
and "to TV" F connector jacks. Or buy a modulator at rat
shack or such place. Okay, nothing special so far.....

Most vintage color TVs use what is known as a "notch filter"
to separate the chroma (color info) subcarrier from the luma
(B&W) signal. Only thing, the higher luma bandwidth is inter-
mixed with the chroma subcarrier on "composite" video
(what you get from the video IF detector). A notch filter is just a band
stop filter from the composite video signal to recover the luma
signal, and a bandpass filter to recover the chroma subcarrier.
A problem is that the higher frequency luma gets misrouted to
the chroma demodulator, resulting in colored crawlies on ref's
shirts in football games.

We can pre-condition the video from a source like a DVD player
that has separate luma and chroma (Y and Ch) outputs, like
an S video connector. We insert into the luma signal a
bandstop filter centered at 3.58MHz. And in the chroma signal
a bandpass filter of 3.58MHz. These then get merged together
to make a new kind of composite video signal that then feeds the
TV modulator. The above color crawlies are greatly reduced if
not completely gone, making for a better looking TV reception
display.

You may need to adjust the level of the new composite video level
feeding the modulator. This can be easily done by increasing or
decreasing the usually 75 ohm termination resistor in the modulator.

The LC values can be different, 600pF and 3uH will have reactances closer to 75 ohms. What's in the diagram yields 350 ohm reactance. which will yield wider passbands. The termination resistor at the modulator will also affect this. I used 150 ohms termination, 130pF and 15uH and got good results.

Below is a picture of a zone plate. Left shows the source image, middle what it looks like on a TV set equipped with a notch filter luma shroma separater, and on the right the same TV set with my preconditioning. Note that the false colors are greatly reduced. A bit less luma resolution, but a peaking circuit should help that.

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Now with peaking on the luma. Revised circuit and screen shots: