Tektronix 7623, Instruction Manual

Page: 45 / 266

Section 3— 7623/R7623 Service
CIRCUIT DESCRIPTION
Introduction
This section of the manual contains a description of the
circuitry used in the 7623 Oscilloscope. The description
begins with a discussion of the instrument using the basic
block diagram shown in Fig. 3-1. Then, each circuit is
described in detail using detailed block diagrams to show
the interconnections between the stages within each major
circuit and the relationship of the external controls and
connectors to the individual stages.
A complete block diagram is located in the Diagrams
section at the back of this manual. This block diagram
shows the overall relationship between all of the circuits.
Complete schematics of each circuit are also given in the
Diagrams section. Refer to these diagrams throughout the
following
circuit description for electrical values and
relationship.
BLOCK DIAGRAM
The following discussion is provided to aid in under­
standing the overall concept of the 7623 before the
individual circuits are discussed in detail. A basic block
diagram of the 7623 is shown in Fig. 3-1. Only the basic
interconnections between the individual blocks are shown
on this diagram. Each block represents a major circuit
within the instrument. The number on each block refers to
the complete circuit diagram located at the rear of the
manual.
Vertical signals to be displayed on the CRT are applied
to the Vertical Interface circuit from both vertical plug-in
compartments. The Vertical Interface circuit determines
whether the signal from the left and/or right vertical unit is
displayed. The selected vertical signal is then amplified by
the Vertical Amplifier circuit to bring it to the level
necessary to drive the vertical deflection plates of the CRT.
Horizontal signals for display on the CRT are connected
to the Horizontal Amplifier circuit from the horizontal
plug-in compartment. The Horizontal Amplifier circuit
amplifies this signal to provide the horizontal deflection for
the CRT.
The internal trigger signals from the vertical plug-in units
are connected to the Trigger Selector circuit. This circuit
selects the trigger signal which is connected to the
horizontal plug-in unit. The Calibrator circuit produces a
square-wave output signal with accurate amplitude which
can be used to check the calibration of this instrument and
the compensation of probes.
The Logic circuit develops control signals for use in
other circuits within this instrument and the plug-in units.
These output signals automatically determine the correct
instrument operation in relation to the plug-ins installed
and/or selected, plug-in control settings, and 7623 control
settings. The CRT circuit produces the voltages and
contains the controls necessary for operation of the
cathode-ray tube. It also contains the Z-Axis Amplifier
which provides the drive signal to control the intensity level
of the CRT display. The storage Logic board produces the
timing necessary for the storage output board to control
the storage operation of the CRT.
The power necessary for the operation of this instru­
ment is produced by the Low-Voltage Power Supply
circuit. These voltages are connected to all circuits within
the instrument.
CIRCUIT OPERATION
This section provides a detailed description of the
electrical operation and relationship of the circuits in the
7623. The theory of operation for circuits unique to this
instrument is described in detail in this discussion. Circuits
which are commonly used in the electronics industry are
not described in detail. If more information is desired on
these commonly used circuits, refer to the following
textbooks (also see books under Logic Fundamentals):
Tektronix Circuit Concepts Books (order from your
local Tektronix Field Office or representative).
Cathode-Ray Tubes, Tektronix Part No.
062-0852-01.
Horizontal Amplifier Circuits, Tektronix Part No.
062-1144-00.
Oscilloscope Trigger Circuits, Tektronix Part No.
062-1056-00.
Power Supply Circuits, Tektronix Part No.
062-0888-01.
Sweep Generator Circuits, Tektronix Part No.
062-1098-01.
Vertical Amplifier Circuits, Tektronix Part No.
062-1145 00.
3-1