[old_tv_nut]

To determine if your particular set has I/Q demodulation, get the schematic and look for the color IC to have an associated I delay line.

Unfortunately, you cannot find a source today that outputs true I/Q modulation (Laserdiscs may be an exception, but I am not sure); however, you will see some improvement in color detail, accompanied by some quadrature distortion, due to current sources having fairly wideband equiband modulation.