VHF Tuner Alignment: where is the overall oscillator adjustment?

[LukeSimon]

Originally Posted by old_coot88

Phase of the burst signal is what the tint control has to regulate, thereby the phase of the 3.58 oscillator. Its output is then referenced to the wideband chroma bandpass signal, to feed the demods.

I got the oscillator to the point where it had its full range of plus or minus 30 degrees. The problem is that the difference between the color burst phase and the chroma signal after bandpass ends up being 90 degrees different. So the 30 degrees is not enough.

The chroma demod acts as a differential amplifier and so it is the difference in phases between the oscillator and the amplified chroma that matters. That difference cannot be more than plus or minud 30 degrees. As the chroma bandpass is adjusted, the chroma signal’s phase is shifted. So having tint follow the bandpass would have made alignment not impact tint since both the burst and the chroma signal’s phases would be shifted together.