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SECTION
3
CIRCUIT
DESCRIPTION
Introduction
This
section
contains
the
theory
of operation of
the
various
circuits
in
the
Type
114.
The
text
is
supplemented
by
two
block
diagrams
inserted
in the
text
and
by
schematics
in
Section
5.
The
reader should follow
the circuits
on
the
dia
grams as
they
are presented
in
the text.
CAUTION
There
is
no
fixed
chassis
ground
for
the
circuit
board used
in
the
Type
114.
A
common negative
point
is
used
instead. This permits
changing
the
polarity
of
the
output by
grounding
the appro
priate side
of
the
power supply.
For
this
reason,
always
connect
probe
grounds
to
the
main
chassis
rather
than
to
a
point
on
the
circuit
board.
Period
Generator
The
Period
Generator
(see Fig. 3-1) supplies
the
trigger
pulse
which
activates
the Width
Generator.
The
trigger
pulse
is
generated
internally,
or
is
derived
from
an externally
gen
erated
triggering
signal,
depending
upon
the
setting of
the
PERIOD switch.
Internal Operation.
When
the
Type 114 is
operating
in
the
internally triggered
modes,
the operation of
the
Period
Generator
is
as
follows:
Transistors
Q115 and Q125
in
conjunction
with
the ap
propriate RC
timing
combination
form
a
free
running
oscil
lator.
At
the
start
of a
cycle
of operation,
Q
115
is
biased
off
and
Q125
is
biased
slightly
on.
The
charge
on
timing
ca
pacitor
C
1
15
has
been
removed by
the preceding
cycle
and
now
starts
charging
toward
a
common
point
voltage
at
an
RC
rate.
As
the
timing
capacitor
charges,
the
voltage
across
it
reaches
a
point
where
it
turns
on
diode
D
1
14
and
transistor
Q
1
15.
At
this
instant
the
circuit
becomes
regenerative
with
Q115
turning
Q125
on
hard,
which
in
turn
biases
Q1
15
into
heavy
conduction.
The
heavy
conduction
of
Q
1
15
removes
the
charge
accumulated
on
timing
capacitor
C115
and
ends
the
cycle.
At
the
instant
Q1
25
is
turned
on
hard
by
Q
115,
the
steep
wave-front
is coupled
through
R131
and
C1
31
to
the
base
of
Q
134,
and
thence
to
pulse
transformer
T131.
The
pulse
out
put
of
T131
is
in
the
order
of
20
nanoseconds
in
width.
External
Trigger
Operation.
When
the
Type
114
is
op
erating
in
the
externally
triggered mode,
the
Pulse
Generator
functions
as
a pulse
shaper.
Period
switch
SW120
discon
nects
the
base
of
Q
1
15
from
the
collector
of
Q1
25
and
re
connects
it
to
the
external
trigger
input
circuit.
SW120
also
connects
the
base
of
Q1
25
to
+25
volts
through
R121
and
disconnects
the
timing
capacitor
from
the
circuit.
Under
these
conditions
none of
the
transistors
in
the
Period
Gen
erator
are conducting.
A
positive
pulse
of
2
to
20
volts
in
amplitude
and
having
a
risetime
of
1
microsecond
or
less
is
required
at
the
EXTERNAL
TRIGGER—INPUT
connector
in
order
to
make
the
transistors
conduct and
deliver
the
proper
pulse
to
the
Width
Generator.
When
a pulse
having
the proper amplitude
and
risetime
is
applied
to
the
EXTERNAL
TRIGGER
—
INPUT
connector,
Q
1
15
is
biased
into
conduction
and
in
turn
biases
Q1
25
and Q134
into
conduction.
The
resulting
pulse
at
the
pri
mary of
T131
has
a
risetime
of
about
10
nanoseconds.
Width Generator
The
Width
Generator
receives
the
trigger
pulses
from
T131
and
generates
pulses
of
the
desired
width.
The
out
put
of
the
width
generator is
applied
to
the Trigger Out
Circuit
and
to
the
Output
Amplifier.
Except
when
operat
ing
in
the
square
wave
mode,
the
Width
Generator
operates
as
a
monostable
multivibrator;
in
the
square
wave
mode
the
Width Generator
functions
as
a
bistable.
Normal
Operation.
In
normal
operation
transistors
Q205
and Q215
form
a
bistable
network
whose
output
drives
ramp
transistor Q224,
trigger
output
transistor
Q234,
and
the
output
amplifier.
Q205
is
the normally “on"
tran
sistor.
The
arrival
of
a
negative
trigger
pulse
from
T131
cuts
off
Q205.
Q215
now
conducts
and
cuts off Q224,
permitting
the voltage
at
the
collector
of
Q224
to
start
charging
ramp capacitor
C195.
When
the selected
ramp
capacitor
reaches
the
desired
voltage,
D
1
93
is
forward
biased
and
transistor
Q
1
94
is
biased
into
conduction.
The
conduction
of
Q1
94
increases
the
conduction
of
Q1
84
and
thereby
biases
Q205 back
into
conduction.
The
conduction
of
Q205
ends
the
output
pulse.
Turning
on
Q205
turns
off
Q215
and
turns
on
Q224. The
conduction
of
Q224
dis
charges
the
ramp
capacitor.
When
the
ramp capacitor
is
discharged
down
to
about
0.3
volt, Q174
turns
off
and Q164
is
turned
on.
Transistors
Q1
64
and
Q1
74,
diodes
D1
36
and
D
161,
and
pulse
trans
former
T131
function
as
a
pulse
steering
circuit.
With
Q1
64
on,
the
pulse
from
the
Period
Generator
via
T131 triggers
the
width
monostable
circuit
on,
generating
an
output
pulse.
As
soon
as
the
ramp
capacitor
reaches
approximately
0.3
volt,
Q174
conducts
and
turns Q164
off.
Turning
off
Q164
reverse
biases
D
1
61,
while
turning
on
Q1
74
biases
D1
36
near
zero.
If
the Period Generator
produces
a
pulse
while
these
conditions
exist,
that
is,
whenever
the
ramp
capacitor
has
a
charge
above
approximately
0.3
volt,
the
pulse
is
steered
to
the
WIDTH
>
PERIOD
light
circuit.
This
mono
stable
circuit
is
actuated
by
the
pulse from T131, turning
off
Q145
and
turning
Q155
on,
lighting
the
WIDTH
>
PERIOD light.
Turning
on
Q1
55
causes
C1
55
to
discharge
through
T131
and
R136.
When
C155
is
discharged,
D141
and
Q
145
conduct
and
reset
the
circuit,
making
it
ready
for
another
pulse.
Square
Wave
Mode.
When
the
Type
114
is
operated
in
the
Square Wave Mode
(see Fig.
3-2),
the
Width
Gen
erator
operates
as
a
bistable
and
requires
two
trigger
pulses
from
the
Period
Generator
for
each
cycle
of
operation.
Consequently,
the
RC
network in
the
Period
Generator
is
3-1
Summary of Contents for 114
Page 3: ...Type 114 Type 114 Pulse Generotor ...
Page 8: ...Operating Instructions Type 114 Fig 2 1 Front panel control Fig 2 2 Type 114 rear ponel 2 2 ...
Page 10: ...NOTES ...
Page 14: ...NOTES ...
Page 28: ...Maintenance and Calibration Type 114 Fig 4 20 Locations of electrical components 4 14 ...
Page 30: ...Parts List Type 114 EXPLODED VIEW 5 2 ...
Page 45: ...TYPE 114 PULSE GENERATOR ...
Page 46: ...PULSE GENERATOR ...
Page 47: ...TYPE IM PULSE GENERATOR c ...
Page 48: ...SW282 POWER SUPPLY CMD OUTPUT AMPLIFIER 4 POWER SUPPLY ...