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T Y P E 1 3 9 8 - A P U L S E G E N E R A T O R
4.4.9 OUTPUT AMPLIFIERS.
Start-Signal Action
As long a s V103A is on, C will not charge, and V103B
will be on, holding C's voltage to V.
Since the multivibrator driver h a s reversed i t s
s t a t e , the output amplifiers have a l s o reversed their
4.4.1
1
AMPLITUDE COMPARATOR SCHMITT
s t a t e s . V105 is now off and the +OUTPUT PULSE
Quiescent: V104A O F F , V104B ON
voltage i s 0 volts, and VlO6 i s now on and the -OUT-
P U T PULSE voltage i s -60 volts instead of 0 volts.
All that remains t o convert t h e s e dc-voltage s t e p s t o
pulses i s t o return the circuits t o their quiescent levels.
4.4.10 SWEEP GENERATOR AND CLAMP,
DURATION CONTROL.
Quiescent: V103A ON, V103B ON
The stop-signal path returns the circuits to their
quiescent levels. T h e time required t o d o t h i s i s the
output p u l s e duration; therefore the PULSE DURATION
controls are located in the s t o p signal path.
Since the voltage V on i t s grid i s held equal to
or lower than i t s cathode voltage, V104A is biased off.
Since V104A and B are a Schmitt circuit, V104B must
be on if V104A is off. V104A will not turn on until the
voltage on i t s grid exceeds the voltage on the grid of
V104B s e t by R127 and R129.
4.4.12 SWEEP GENERATOR
A N D
CLAMP.
Stop-Signal Action
When V105 reverts from i t s quiescent s t a t e , it
turns off. Vi03A a l s o turns off because both tubes share
a common bias. When V103A turns off, capacitor C
begins t o charge t o + I 5 0 volts. As it charges, it draws
current through the plate load resistor, R , of V103A
T h e duration is actually controlled by a sweep
and thus keeps the plate of V103A from returning im-
generator whose sweep rate can be adjusted by the
mediately t o + I 5 0 volts.
DURATION controls. Before the arrival of a start
pulse a l l circuits are in their quiescent s t a t e s . V105 is
on, and since the grid bias of V105 is a l s o t h e grid
b i a s of V103A,V103A i s a l s o on in the quiescent state.
T h e diode V103B is connected between C and a
t a p on the cathode resistor R125 ( t h e PULSE DURA-
TION control) of the Schmitt circuit comprised of
V104A and B. T h i s resistor carries a constant current
( a b o u t 15 milliamperes) s o that the voltage V a t the
t a p is constant. T h i s positive voltage forms the b a s e
from which the ramp pulse of the sweep generator r i s e s .
Therefore, the voltage a t the plate of V103A
goes positive at a rate determined by the values of C
and R. When t h i s voltage goes more positive than V,
V103B turns off. When the voltage reaches the switching
voltage of the Schmitt trigger-circuit, V104A turns on
and V104B turns off. The length of time it t a k e s the
voltage on C to reach this level depends on the base
voltage V: if V i s tapped from the top of R125, the
time is short; if V is zero (tapped from the bottom),
time is long. When V104B turns off, a positive pulse i s
applied to the stop-trigger amplifier.
d
.
--"
R501
-
- -
V501A
t 1 5 0 V REGULATED
-
R 5 0 4
R 5 0 5
R 5 0 6
m
-150V REGULATED
I I
( - 1 5
0
REGULATED
F i g u r e
4-6.
S i m p l i f i e d schematic diagram
of t h e power-supply c i r c u i t .
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