Datapulse 101 - Page 21

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When Q10 is cut off, the voltage at its emitter which is initially
at ground starts to build up because of the charging of the timing capacitors
(C70 through C75) through timing resistors R71 and R72. When this voltage
reaches the voltage of the base of Q10 which is determined by the setting of
delay potentiometer R75, 010 starts to conduct again. A regenerative turn—
on of both transistors follows with Q10 turning 011 on and Q11 reinforcing
the turn—on at the base of Q10.
The basic period is determined by the timing capacitors which are
selected for decade ranges and vernier fill-in is provided by delay potenti-
ometer R75. The collector of Q11 is allowed to make a full 12 volt ampli-
tude output by the disconnect action of diode CR70. The output pulse is
differentiated at the collector of 011 by inductor L70 and resistor R77.
3. 2, 6 Pulse Transformer
Pulse transformer T70 is used to provide the several outputs required
of the circuit. As shown in the schematic, the transformer windings which
have dots have a positive spike at the beginning of the delay period and a
negative spike at the end.
In
order
for
the
width
multivibrator
to
operate
properly
in
the
single
pulse
mode
it
must
receive
a
negative
trigger
from
the
pulse
trans-
former
at
the
end
of
the
delay
period.
In
the
double
pulse
mode,
it
must
receive
a
negative
trigger
at
both
the
beginning
and
the
end
of
the
delay
period.
These
two
requirements
are
met
by
connecting
opposite
ends
of
two
windings
of
the
pulse
transformer
and
applying
the
resulting
pulse
waveforms
through
the
diode
mixers
CR72
and
CR73.
The
pulse
mode
switch
S71
disconnects
the
negative
output
appearing
at
the
beginning
of
the
delay
time
during
single
pulse
operation.
3.2. 7 Reference Trigger Amplifier
An additional output is taken from the pulse transformer at the
beginning of the delay period as a negative trigger and applied to the base of
012, the reference trigger amplifier. These triggers will be counted down
if the period of the delay generator is longer than the period of the incoming
triggers. 012 responds only to the negative going triggers at its base and
produces a positive pulse into 51 ohms (R81) at its collector for the reference
trigger output. Diode CR71 prevents 012 from being turned on by the current
available from +12 volts through R79 until the negative base signal appears
and also keeps (.212 from being responsive to the positive portion of the base
waveform.
3. 2. 8 Width Multivibrator
The width multivibrator circuit is the same as the delay multivibrator
circuit and consists of transistors 013, 014 and their related circuit components.
The input trigger is supplied by the pulse transformer. The basic width ranges,
in decade steps are determined by timing capacitors C90 through C95 with
vernier fill-in supplied by width potentiometer R95. The output from the
collector of Q14 is applied to the output driver stages across resistor R96.
3-6