Section 4 -4 5 5 /A2/B2
CIRCUIT DESCRIPTION
CAUTION
SERVICING INFORMATION IN THE FOLLOWING SECTIONS IS IN
TENDED FOR USE BY QUALIFIED SERVICE PERSONNEL ONLY. TO
AVOID ELECTRIC SHOCK, DO NOT REMOVE INSTRUMENT COVERS
OR PERFORM ANY SERVICING UNLESS QUALIFIED TO DO SO.
This section describes the circuitry used in the 455/A2/B2 Oscilloscope. The description begins with a discussion of the basic
circuit functions of each module, then expands into a detailed description of the individual circuits. Refer to the Block Dia
grams and the schematic diagrams in the Diagrams section.
BASIC CIRCUIT FUNCTIONS
455 MAIN MODULE
Most of the 455 circuitry is contained on the main circuit
board which is mounted on the lower part of the module.
The 455 Main Module contains the basic display functions
of the oscilloscope. It houses the Calibrator, Sweep Gate
Amplifier, Horizontal Output Amplifier, Z Axis Amplifier,
CRT, and Power Supply circuits.
The Calibrator circuit produces a square-wave output with
an accurate voltage amplitude for checking instrument
calibration and compensating probes.
The Sweep Gate Amplifier amplifies the sweep gate signal,
from the Horizontal Module, for output through the + GATE
OUT connector at the rear of the instrument.
The Horizontal Module output connects to the Horizontal
Output Amplifier through the interface connector. The
Horizontal Output Amplifier amplifies the signal from the
Horizontal Module to drive the crt horizontal deflection
plates.
The Z Axis Amplifier circuit determines crt intensity and
blanking. It sums the blanking signals from the Vertical
Module, Horizontal Module and the EXT Z AXIS IN con
nector. The output level of the Z Axis Amplifier circuit
controls the display intensity through the CRT circuit. The
CRT circuit provides the voltages and controls to operate
the crt.
The Power Supply circuit provides the low-voltage power
(except +95 volt which is developed in the CRT circuit)
necessary for operation of the entire oscilloscope. Voltages
are distributed to the Vertical and Horizontal Modules
through the interface connectors.
The crt vertical deflection plates are driven directly by the
output signal from the Vertical Module.
A2 VERTICAL MODULE
The A2 circuitry is contained on a single circuit board.
The Preamplifier and Switching circuits are contained
within a single Hybrid Integrated circuit (HIC). The HIC
is mounted in a special interface connector centered on the
circuit board.
The A2 Vertical Module contains the Channel 1 and Channel
2 input, vertical Preamplifier, channel Switching Gates and
Vertical Output Amplifier circuits.
Signals to be displayed on the crt are applied to the CH 1 OR
X and/or CH 2 OR Y BNC connectors. The input signals are
then amplified by the preamplifier circuitry. Each pre
amplifier circuit includes separate vertical-deflection factor,
input coupling, balance, gain, and variable attenuation con
trols. The vertical deflection factor for each channel is
indicated by two small lights located close to the skirt of
each VOLTS/DIV knob. The right indicator lights up to
show the correct deflection factor when a 10X probe with a
scale-switching connector is used. The left indicator lights
when a probe without the scale-switching connector (or no
probe) is used.
REV. A, OCT 1975
4-1
To Next Page
Loading...
Need help?
General
