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HP 212A - Pulse Terminating Thyrntron V L; Clipper; Output Amplifier

HP 212A
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3-7
PULSE
TERMINATING
THYRATRONVlb
The
pulse
from
tube
V109B
triggers
the
pulse terminating
thyratron
Vlb.
When
fired,
this
thyratron
in
conjunction
with the
discharge
diode
V8
presents
a
very
low
impedance
to
the
pulse
from
the
pulse
forming
thy-
ratron
V6
and
causes
a
rapid
fall
of
the
pulse
to
form
the
trailing
edge.
Additional
direct
current
voltage
is
supplied
to
Vlb
by
means
of
R28
and
allows
the pulse terminating thyratron
to
fire
when
the
pulse
length
is
set
to
a
very
low
value.
Tube
V8
in
conjunction
with
R10
and
C24
allows
the
thyratron
V16
to
be
extinguished
at
the
end
of
the
pulse
cycle.
3-8
CLIPPER
CIRCUITS
The
pulse
from
the
thyratron
is
sent
through
a
series
of
three
diode
clip-
pers
and
then
to
the
output
amplifier
tube
V
11.
Tube
V7
is
the
first diode
clipper.
Tube
V9
is
the
second
and third diode
clipper.
3-9
OUTPUT
AMPLIFIER
The
output
amplifier
tube V11
feeds
the
polarity
switch
where
either
a
plus
or
minus
pulse
may
be
selected
and
applied
to
the
attenuator.
The
attenuator
is
then
used
to
reduce
the
pulse
10
db
steps.
Intermediate
values
a£
amplitude
may
be
selected
by
means
of
the
AMPLI-
TUDE
control
which
has
a
continuous
range
of
more
than
10
db.
This
control
consists
of
two
ganged
variable
resistors
which
vary
the
grid
bias
and
plate
voltage
on
the
output
amplifier
tube
V11
and
the
cath-
ode
voltage
on
the
two
clipper
tubes
V7
and
V9.
In
order
to
provide
a
more
constant
pulse
output amplitude
with
changes
in
repetition
rate
and
pulse
width,
a
compensation
circuit
is
incorporated
in
the
unit.
When
the
rate
or
pulse
width
is
increased,
a
positive
volt-
age
is
applied
to
the
cathode
of
V15
through
R51
which
causes
the
voltage
to
the
plate
of
the output
tube
and
bias
of
the
clippers
to
increase
thereby
compensating
for
the
otherwise
decrease
in
output amplitude
when
the
rate
or
pulse
width
is
increased.
The
power supply
circuits
are
conventional,
and
the
direct
current
supply
voltages
are
regulated
either
by
glow
discharge
type
regulator tubes
(V4,
V12,
VL4)
or
by
electronic
regulators
(VlOB,
VL7A,
V17B).
Tubes
VlOF
and
V17B
are
used
to
regulate
the
t300V
supply.
Tubes
V15
andV17
re-
gulate
the
voltage
supplied
to
the
clipper
and
output
amplifier
circuits.

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