Options—
465B Service
Option 05
oscilloscope
is correct. However, the
vertical divisions
represent
only proportions of the
100-unit (CCIR) or
140-
unit (NTSC) video
waveform, and the vertical
VOLTS/DIV
calibration is inapplicable.
To
calibrate
for a standard
1 volt (nominal) studio video
signal, apply
the 300 millivolt CALIBRATOR
waveform
to
the Vertical
input and adjust the
VOLTS/DIV and VAR
controls
so
that the
displayed waveform
occupies just 30
units (CCIR
graticule) or 42 units (NTSC
graticule). This
adjustment may be performed
with a free-running sweep.
Operation of the Sync Separator
To trigger
the 465B on a video signal, perform the
following three
steps:
1
Set
the
A TRIGGER COUPLING switch to either TV
FIELD or TV LINE
2 Apply
a
suitable
Composite Sync or Composite
Video waveform to the A External
Trigger input connector
NOTE
Composite Sync is combined Vertical and
Horizon-
tal sync as a single waveform,
but without video
(picture) waveforms. Composite Video
is the picture
waveform complete with Vertical
and Horizontal
blanking and sync.
For special considerations
in Dual Trace modes (ALT
and CHOP), refer
to Vertical Operating Modes—Special
Considerations in this section For internal triggering, the
sync
portion of the displayed waveform should
be at least
10 units, or
0.5
division on the CCIR graticule, 14 units, or
about
0
75 division on
the
NTSC
graticule. For external
triggering,
the
sync portion
of the waveform should be at
least
75 millivolts in amplitude, or
0
75 volt in the EXT/10
mode. Do
not
exceed the indicated maximum amplitudes
(20 divisions for
internal
triggering, 40 volts for
external
triggering), to avoid circuit overloads and partial or
complete loss of sync.
3. Select the proper polarity
for the video waveform
applied.
For normal video with
sync at the negative peak
and positive-going picture information, the A TRIGGER
SLOPE switch should be set to minus
(
);
for inverted
video having sync at the positive
peaks and peak video
(white) at the negative
peaks, the SLOPE switch should be
set
to plus
(+).
The
A TRIGGER SLOPE switch controls an
inverting/non-inverting signal preamplifier
ahead of
the
sync separator
Triggering the Sweep
The output of the Sync Separator is fed directly to the A
Sweep
Trigger circuit; all that is required for triggering is
the proper setting of the A TRIGGER LEVEL control To
trigger the B Sweep from the Line-rate trigger output,
perform the following steps
1 Make
sure
the A Sweep is running
NOTE
The B Sweep cannot be
operated
independently and
cannot run more than once per operation of the A
Sweep.
For
Composite line displays,
refer
to
Special
Measurements in this
section.
2.
Set the B
TRIGGER
SOURCE
switch
to TV
LINE
3. Set the B
TRIGGER
LEVEL control for a stable
triggered
sweep.
Vertical
Operating Modes—Special
Considerations
DUAL TRACE MODES.
For dual trace operation, the
Sync Separator
input must
be
taken from
Channel
1,
Channel
2,
or an external source
(When only one trace is
displayed, the NORM position
of the A TRIGGER
SOURCE switch may be used.)
The Sync Separator is
not
capable of correct
processing of switched (composite
vertical deflection) waveforms
present
on
the NORM bus
in the
ALT or CHOP modes; it is therefore
not possible to
obtain stable simultaneous
displays of two
independent
video signals that are
not time-related.
SINGLE
CHANNEL TRIGGERING. When triggering
from Channel
1 or
Channel
2,
the waveform fed to the Sync
Separator
is the same (except for positioning) as that
displayed on-screen when the channel is turned on. If the
VOLTS/DIV VAR control is used to reduce displayed
amplitude, the signal to the Sync
Separator is also
reduced When the CH 2 INVERT switch is pushed in,
the
Channel 2
signal
to
the A TRIGGER SOURCE switch is
also inverted.
Therefore, in selecting the position of the A
TRIGGER SLOPE switch in internal triggering, it is only
necessary to note the polarity of the
displayed waveform,
disregarding
its
actual polarity as applied to the Vertical
INPUT
connector.
For
external triggering, the actual
applied
polarity will determine the necessary A TRIGGER
SLOPE setting
It is not necessary to
display Channel 1 or Channel 2 to
obtain CH 1 or CH 2 triggering.
Whenever the AC-GND-
DC switch for the channel is
not
in
GND, the input
amplifier and trigger channel are active, regardless of the
selection
of
VERT MODE push buttons.
67
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