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Installation and Operation, cont'd
5.
Connect scope probe B to the VSC's composite video
output connector.
6.
Using the instructions for the scope you are using, set
the scope to view the signal's horizontal phases.
Adjust the horizontal phase by rotating the Adjust
horizontal (
section in this chapter). Adjust the horizontal phase
until there is no (0°) difference between the
composite video output's horizontal sync phase and
the genlock signal's horizontal phase. See the
"Oscilloscope displays" section in this chapter.
7.
Set the scope to view the subcarrier signals. Adjust
the sub phase by rotating the Adjust vertical ( )
knob until there is a zero phase difference between
the genlock signal and the NTSC/PAL output (see
the "Genlock menu" section in this chapter).
8.
View the horizontal phases again. If the phase
difference is not zero, repeat steps 6 and 7 until the
settings do not change.
9.
Once the settings are stable, disconnect the
oscilloscope, and reconnect the genlock cables.
10.
Check the display(s) for proper colors and for
undesirable artifacts in the image(s). Make
adjustments as necessary.
11.
If other VSCs are part of this genlock daisy chain,
connect the oscilloscope to each device, and repeat
this procedure.
Oscilloscope displays
What you see on the oscilloscope while adjusting the VSC to
match the genlock signal depends on the type of signal used, the
type of oscilloscope, and the procedure the scope requires. This
section shows some examples of oscilloscope displays.
The following diagram shows the genlock input signal (top) and
an out-of-alignment NTSC composite sync output signal
(bottom) displayed on a waveform monitor to check for
alignment. When the phases are aligned, the wave peaks on the
bottom waveform should line up with those in the reference
signal above it.
2-8
VSC 500/700/700D • Installation & Operation
) knob (see the "Genlock menu"
Superimposed waveforms
With this method there is no way to know if the signals are 180º
out of phase. A delayed sweep on a time-based scope would
allow a more accurate display of the input and output signal
phase relationships.
A vectorscope is more accurate than a waveform monitor. The
following diagram shows an example of a vectorscope display
when the horizontal phase is adjusted to align it with the burst
(genlock) vector. Adjust the horizontal phase by rotating the
Adjust horizontal (
) knob until the difference between the
two vectors is 0º. This example shows black burst only (with no
color). The burst vector is pointing to the left from the center.
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Vectorscope screen during horizontal
phase adjustment
VSC 500/700/700D • Installation & Operation
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