Section
3-2445A/2455A
Service
THEORY OF OPERATION
INTRODUCTION
SECTION ORGANIZATION
This section contains a functional description of the
instrument circuitry. The discussion begins with
an
over-
view
of the instrument functions
and
continues with
detailed explanations of
each
major circuit. Reference
is
made to supporting schematic
and
block diagrams which
will facilitate understanding of the text. These diagrams
show interconnections between parts of the circuitry, iden-
tify circuit components, list specific component values,
and
indicate interrelationships with front-panel controls.
The
detailed block diagram
and
the schematic diagrams
are located
in
the tabbed "Diagrams" section at the rear of
this manual, while smaller functional diagrams
are
con-
tained within this section near their respective text. The
particular schematic diagram associated with
each
circuit
description
is
identified
in
the text,
and
the diagram
number
is
shown (enclosed within a diamond symbol)
on
the tab of the appropriate foldout
page.
For optimum
understanding of the circuit
being
described, refer to both
the applicable schematic diagram
and
the functional block
diagram.
HYBRID AND INTEGRATED CIRCUIT
DESCRIPTIONS
Digital Logic Conventions
Digital logic circuits perform many functions within this
instrument. The operation of these circuits
is
represented
by specific logic symbology
and
terminology. Most logic-
function descriptions contained
in
this manual
use
the
positive-logic convention. Positive logic
is
a system of
notation whereby the more positive of two levels is the
TRUE (or
1)
state; the more negative
level
is the FALSE
(or
0)
state.
In
the logic descriptions, the TRUE state
is
referred to
as
HI,
and
the FALSE state is referred to
as
LO
.
The
specific voltages which constitute a
HI
or a
LO
state vary between individual devices. For specific device
characteristi
cs,
refer to the manufacturer's data book.
Hybrids
Some of the circuits
in
this instrument are implemented
in
hybrid devices. The hybrids are specialized electronic
devices combining thick-film
and
semiconductor technolo-
gies. Passive, thick-film components
and
active, semicon-
ductor components
are
interconnected to form the circuit
on
a ceramic carrier. The
end
result
is
a relatively small
"building block" with enhanced performance characteris-
tics,
all
in
one package. Hybrid circuits are shown
on
schematics simply
as
blocks with inputs
and
outputs.
Information about hybrid functioning
is
contained
in
the
related portion of the Detailed Circuit Description.
Linear Devices
The operation of individual linear integrated circuit
devices
is
described
in
this section using waveforms or
other graphic techniques to illustrate their operation.
BLOCK DIAGRAM
The following discussion
is
provided to
aid
in
under-
standing the overall operati
on
of the instrument circuitry
before the individual circuits are discussed
in
detail. A
simplified block diagram of the instrument, showing basic
interconnections,
is
shown
in
Figure 3-1. The diamond-
enclosed numbers
in
each
block refer to the schematic
diagram(s) at the rear of this manual
in
which the related
circuitry
is
located.
BLOCK DESCRIPTION
The
Low Voltage Power Supply is a high-efficiency,
switching supply with active output regulation that
transforms the
ac
source voltage to the various
de
volt-
ages required
by
the instrument. The
High
Voltage Power
Supply circuit develops the high accelerating potentials
required
by
the crt, using voltage multiplication techniques,
and
the
DC
Restorer provides interfacing for the low-
potential intensity signals from the
Z-Axis Amplifier to the
crt control grid.
3-1
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