Controls, Connectors,
and
Indicators
@
5-8
VOLTS/DIV
Switches
Input
Coupling
Buttons and
Indicators
1
MOAC
1
MO
GND
(2 identical
positions)
Select vertical deflection factor settings
in
a 1-2-5
sequence with
11
positions. The VAR control must be
in
the detent (fully clockwise) position to obtain a calibrated
deflection factor. Basic deflection factors are from 2 mV
per division
to
5 mV per division. The switches can
rotate continuously, but have no effect beyond the
extreme settings. Deflection factors shown
in
the CRT
readout reflect
actual deflection factors when Tektronix
attenuation-coded probes are connected to the inputs.
Select the method
of
coupling input signals
to
Channel 1
and Channel 2 and indicate the selection made.
If the
upper Channel 1 and Channel 2
Input Coupling buttons
are both pressed together, the instrument automatically
performs a dc balance of Channel 1
and
Channel 2
vertical circuitry.
Input signal is capacitively coupled
to
the vertical
attenuator. The dc component
of
the input signal is
blocked. The low-frequency
limit
(-3
dB point)
is
10Hz
or less when using either a 1 X probe or a
coaxial cable and
is
1 Hz or less when using a
properly compensated
10X probe.
Only with the available Television/Video (TV)
enhancement, the
CH
2 input has a back porch
clamp for composite video
Signals. When the input
coupling is AC, pressing the upper button activates
the clamp and displays
"TVC'
in
the readout. The
clamp locks the back porch feature of the video
signal to a constant
level and eliminates drift, hum,
and tilt, despite changes
in
signal amplitude and
average luminance
levels. Pressing the lower button
restores
AC coupling and turns off the clamp.
The input of the vertical amplifier
is
grounded
to
provide a zero (ground) reference-voltage display.
Input resistance is 1
Mfl
to
ground. This input
selection
allows precharging
of
the input-coupling
capacitor
to
prevent a sudden shift of the trace if AC
input coupling
is
selected later. The input signal
is
not grounded. If the input coupling of a channel
selected as
an
A-Trigger source is set at GND, the
A-Sweep free runs. However, when A
TRIGGER
SOURCE
is set
to
VERT and the Add vertical display
is
selected, the sweep free runs only if both Channel
1 and the Channel 2 input couplings are set
to
GND.
While power
is
off, coupling is at 1
Mfl
GND.
2465A/2455A/2445A Operators
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