Theory of Operation—2213 Service
circuit functions to either produce no delay, display an
intensified zone on the Sweep display, or to delay the
start of the Sweep for a period of time after receiving a
triggering signal. The delay time is established by two
front-panel controls: the DELAY TIME switch which sets
the basic delay, and the MULTIPLIER potentiometer
which increases the basic delay by a factor o f up to twenty
times. Output signals from the Delay circuit are applied to
a logic gate circuit to control both the timing of the start
of the sweep and the Z-Axis drive.
The Z-Axis drive from the Sweep Logic circuit is applied
to the Z-Axis amplifier. The output signal from the Z-Axis
Amplifier circuit sets the crt intensity. A Chop Blanking
signal from the Chop Oscillator circuit blanks the crt
display during the transition between the vertical channels
when using CHOP VERTICAL MODE.
The DC Restoration circuit raises the output level of the
Z-Axis Amplifier to allow it to be coupled to the crt
control grid. Direct coupling is not employed due to the
amplitude of the voltage levels applied to the crt elements.
The Swp Duty signal from the Sweep Logic circuit is
applied to the Auto Intensity circuit. The Auto Intensity
circuit provides partial control of the intensity of the
display when switching between different positions of the
SEC/DIV switch.
The Power Supply provides all the necessary operating
voltages for the instrument circuitry. Operating potentials
are obtained from a circuit composed of the Preregulator,
Inverter and Transformer, and Rectifiers and Filters. The
Preregulator produces approximately +45 V from the ac-
power-input source which is used to drive the 20-kHz
Inverter stage. The Transformer secondary windings provide
various ac levels that are rectified and filtered to produce
the operating voltages. A High-voltage Multiplier circuit
produces the accelerating, focus, and cathode potentials
required by the crt.
A front-panel PROBE ADJUST output is provided for
use in adjusting probe compensation. The voltage at the
PROBE ADJUST connector is a negative-going square wave
that has a peak-to-peak amplitude of approximately 0.5 V
and a repetition rate o f approximately 1 kHz.
DETAILED CIRCUIT DESCRIPTION
VERTICAL ATTENUATORS
Both the Channel 1 and Channel 2 Attenuator circuits,
shown in Diagram 1, are identical in operation. In the
following discussion, only the Channel 1 Attenuator circuit
is described. The matching components in the Channel 2
Attenuator circuit perform the same function.
The Attenuator circuit (see Figure 3-2) provides control
of input coupling, vertical deflection factor, and variable
volts-per-division balance. Input signals for crt vertical
deflection may be connected to either or both the CH 1 OR
X and the CH 2 OR Y input connectors. In the X-Y Mode
of operation, the signal applied to the CH 1 OR X con
nector provides horizontal (X-Axis) deflection for the
display, and the signal applied to the CH 2 OR Y connect or
provides the vertical (Y-Axis) deflection for the display.
Input Coupling
The signal applied to the CH 1 OR X input connector
can be ac-coupled, dc-coupled, or internally disconnected
from the input of the High-Z Input Attenuator circuit.
Signals applied to the CH 1 input connector are routed
through resistor R101 to Input Coupling switch S101.
When S I01 is set for dc coupling, the CH 1 signal is applied
directly to the input of the High-Z Attenuator stage. When
ac-coupled, the input signal passes through R100 and
dc-blocking capacitor C l02. The blocking capacitor
prevents the dc component of the input signal from being
applied to the Attenuator circuit. When S101 is set to
GND, the direct signal path is opened and the input of the
attenuator is connected to ground. This provides a ground
reference without the need to disconnect the applied signal
from the input connector. The coupling capacitor is
allowed to precharge through R102, a high-resistance com
ponent, which is connected across Input Coupling switch
S101 in the GND position.
High-Z Attenuator
The first section of attenuator switch S105A directs
the input signal to one of three paths: directly through
R103 (no attenuation); through a 10X attenuator con
sisting of C l05, C l07, R105, R106, R107, and R108;
or through a 100X attenuator consisting of Cl 11, Cl 12,
R110, R111, R112, R114, and R115. Medium-frequency
normalization of the input capacitance is accomplished by
3-4
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