Model 120B Section IV
Paragraphs 4-1 to 4-8
SECTION IV
PRINCIPLES OF OPERATION
4-1. OVERALL BLOCK-DIAGRAM 4-6. The sync signal selected by the TRIGGER
SOURCE switch is-applied to the sweep generator,
DESCRIPTION. wherein the sync signal initiates the horizontal sweep
signal and the unblanking gate. The sweep generator
4-2. The oscilloscope is comprised of five major
applies the sweep signal to the horizontal amplifier,
functional circuit groups: the vertical amplifier, the
and the resultant amplified sweep is applied to the
sweep generator, the horizontal amplifier, the low-
crt as the horizontal deflection signal. unblank- The
voltage power supply, and high-voltage the power sup-
ing gate is applied to the high-voltage power supply.
ply (see figure 4-1).
If an external horizontal sweep is being applied in
4-3. The vertical input signal is applied to the ver- place of the sweep from the sweep generator, the ex-
tical amplifier through a frequency -compensated at- ternal sweep is amplified by the horizontal amplifier
tenuator. The vertical amplifier converts the vertical and applied to the crt.
input to two 180-degree-out-of -phase signals and ap-
plies the amplified signals to the crt as the vertical
4-7. The low-voltage power supply receives 115/230-
deflection; in addition, the vertical amplifier applies
volts, single-phase power from the line andgenerates
the signals to the TRIGGER SOURCE switch, when
the following output voltages: 6.3 volts ac, a regu-
they are used as the INT+ and INT- sync signals.
lated +19 volts dc, +99 volts dc, +I00 volts dc, -150
volts dc, +300 volts dc, and an unregulated +420 volts
4-41 The horizontal or sync input signal is applied to
dc. These voltages are distributed, as required, to
the HORIZONTAL DISPLAY switch. Depending on the
the high-voltage power supply, the vertical amplifier,
setting of this switch, the signal is applied to either
the horizontal amplifier, and the sweep generator.
the TRIGGER SOURCE switch (to be used as the ex-
ternal sync signal) or to the horizontal amplifier (to
be used as the external horizontal input signal).
4-8. The high-voltage power supply generates the
4-5. In addition tothe internal and external sync sig- high voltages for the crt. The unblanking gate and
nals, the TRIGGER SOURCE switch receives 6.3 volts Z-axis signals applied to high-voltage the power .sup-
ac from the low-voltage power supply; this provides ply effectively alter the value of the power-supply
for a sync-signal repetition rate equal to the line- voltages to allow unblanking and modulation of the crt
voltage frequency. intensity.
VERTICAL DEFLECTION \
*
VERTICAL
GENERATOR HORIZONTAL SWEEP
( I OF 3 SECTIONS )
>TO CRT
HIGH VOLTAGE
b
POWER FOCUS VOLTAGE
- SUPPLY +
INTENSITY VOLTAGE
-+
LOW
115/230 VOLTS 1
60 CPS 6 3 VOLTS AC
POWER
l PHASE
SUPPLY D-C VOLTAGE AND SWEEP
CIRCUIT
80-"-266
Figure 4-1. Overall Block Diagram
4-1 |
ACEC
