Circuit Description; Block Diagram; Block Diagram Description; Circuit Operation - Tektronix 7704A Instruction Manual

Section 2—7704A Service
CIRCUIT DESCRIPTION
This section of the manual describes the circuitry used in the 7704A Oscilloscope System. The description begins with a
discussion of the instrument, using the basic block diagram shown on Fig. 2-1. Next, each circuit is described in detail, using
detailed block diagrams when appropriate, to show the relationship between the stages in each major circuit. Detailed
schematics of each circuit are located in the Diagrams section at the back of this manual; refer to these schematics throughout
the following circuit description for specific electrical values and relationships.
BLOCK DIAGRAM
The basic block diagram in Fig. 2-1 shows the basic
interconnections between the individual blocks; each block
representing a major circuit within the instrument. The
numbered diamond in each block refers to the circuit
diagram (located at the rear of the manual) which covers
that specific part of the instrument.
Block Diagram Description
Vertical signals from both vertical plug-in compartments
are applied to the Vertical Interface circuit. This circuit
determines whether the signal from the left or right vertical
plug-in unit is displayed. The selected vertical signal is then
amplified by the Vertical Amplifier circuit to drive the
vertical deflection plates of the CRT. The Vertical
Amplifier circuit also accepts the Y-Readout signal from
the Readout System to produce the vertical portion of the
alpha-numeric readout display.
The Readout System provides an alpha-numeric display
for information encoded by the plug-in units. This display
is presented on the CRT on a time-shared basis with the
analog waveform display.
Horizontal signals from both horizontal plug-in
compartments are connected to the Horizontal Interface
circuit. This circuit determines whether the signal from the
A or B horizontal unit is displayed. The selected signal is
connected to the Horizontal Amplifier circuit, where it is
amplified to provide the horizontal deflection for the CRT
beam. The Horizontal Amplifier circuit also accepts the
X-Readout signal from the Readout System to produce the
horizontal portion of the readout display.
The Logic Circuit develops control signals for use in
other circuits within the instrument and plug-in units.
These control signals automatically determine the correct
operation of the instrument in relation to the plug-in
installed or selected, the plug-in control settings, and the
7704A control settings.
REV. B, MAY, 1976
The internal trigger signals from the vertical plug-in are
connected to the Trigger Selector circuits. These circuits
select the trigger signals to be applied to the sweep circuits
in the horizontal plug-in units. The B Trigger Selector also
supplies the drive signal for the Vertical Signal Output.
In addition to the Vertical Signal Output mentioned
above, the Output Signals circuit also provides a +Sawtooth
Out signal derived from the A or B horizontal sweep signals,
and +Gate Out and readout triggering signals derived from
the A or B horizontal gate signals.
The Calibrator circuit produces a one-kilohertz
square-wave output. This signal is available as a voltage at
the tront-panel CALIBRATOR connectors or as a current
through the 40 milliampere current-loop adapter available
as an optional accessory.
The Inverter/Rectifiers circuit provides the low-voltage
power necessary for operation of the entire instrument. The
high voltages needed for the CRT are supplied by the CRT
Circuit. The CRT Circuit also contains the Z-Axis Amplifier
which provides the drive signal to control the intensity level
of the display.
CIRCUIT OPERATION
This section provides a detailed description of the
electrical operation and relationship of the circuits in the
7704A. The theory of operation for circuits unique to this
instrument is described in detail in this discussion. Circuits
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):