Tektronix 465 User Manual

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Section 3-465
CIRCUIT DESCRIPTION
Introduction
This section of the manual contains a description of the
circuitry used in the 465 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 in each major
circuit and the relationship of the front panel controls 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
relationships.
Digital Logic
Digital logic techniques are used to perform many
functions within this instrument. The function and opera-
tion of the logic circuits are described using logic sym-
bology and terminology. All logic functions are described
using the positive logic convention. Positive logic is a
system of notation where the more positive of two levels
(HI) is called the true or 1 state; the more negative level
(LO) is called the false or O state. The HI-LO method of
notation is used in this logic description. The specific
voltages which constitute a HI or LO state vary between
individual devices. Typical HI and LO logic levels are shown
on the diagrams at the rear of this manual.
It should be noted that not all of the integrated circuit
devices in this instrument are digital logic devices. The
function of non-digital devices will be described indi-
vidually using operating waveforms or other techniques to
illustrate their function.
BLOCK DIAGRAM
General
The following discussion is provided to aid in under-
standing the overall concept of the 465 Oscilloscope before
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the individual circuits are discussed in detail. A basic block
diagram of the 465 Oscilloscope 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 which is located at
the rear of this manual.
Signals to be displayed on the CRT are applied to the
CH 1 OR X and/or CH 2 OR Y connectors. The input
signals are then amplified by the Preamp circuits. Each
Preamp circuit includes separate vertical deflection factor,
input coupling, balance, gain, and variable attenuation
controls. A trigger pickoff stage in each Vertical Preamp
circuit supplies a sample of the channel signals to the
Trigger Generator circuit. A sample of the Channel 1 signal
is also supplied to the CH 1 VERT SIGNAL OUT BNC
connector on the instrument rear panel. In the X-Y mode
of operation the Channel 1 signal is connected to the input
of the Horizontal Amplifier circuit to provide the X-Axis
deflection. The Channel 2 Vertical Preamp circuit contains
an invert feature to invert the Channel 2 signal as displayed
on the CRT. The output of both Vertical Preamp circuits is
connected to the Vertical Switching circuit. This circuit
selects the channel(s) to be displayed. An output signal
from this circuit is connected to the Z Axis Amplifier
circuit to blank out the switching transients between
channels when in the chopped mode of operation. A trigger
pickoff stage at the output of the Vertical Switching circuit
provides a sample of the displayed signal(s) to the Trigger
Generator circuit.
The output of the Vertical Switching circuit 1s con-
nected to the Vertical Output Amplifier through the Delay
Line. The Vertical Output Amplifier circuit provides the
final amplification for the signal before it is connected to
the vertical deflection plates of the CRT. This circuit
includes the BEAM FIND switch which compresses the
vertical and horizontal deflection to within the viewing area
to aid in locating an off-screen display.
The A and B Trigger Generator circuits produce an
output pulse which initiates the sweep signal produced by
the A or B Sweep Generator circuits. The input signal to
the A and B Trigger Generator circuits can be individually
selected from the Channel 1 signal, Channel 2 signal, the
signal (s) displayed on the CRT, a signal connected to the
external trigger input connectors, or a sample of the line
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Tektronix 465 Specifications

General

Brand	Tektronix
Model	465
Category	Test Equipment
Language	English