TM 9-4931-294-15/2
rectified in bridge rectifier CR701 through CR704, and is
back voltage is fed through emitter follower Q302 to the
filtered by capacitor C701. After control relay K702 is
base of pass transistor Q301, where, by controlling the
energized, additional filtering is provided by choke L701
emitter to collector resistance, regulation of the 22.5volt
and capacitor C701. The 40volt unregulated output is
output is maintained.
then fed to transistors Q709 and Q706 in the
preregulator circuit.
receives the ac voltage from T701.
The ac is
Figure 2-9. 40 Volt Power Supply, Block Diagram.
d. Helix and Collector Supplies. The helix and
resistance of Q709 is increased, thereby lowering the
input voltage to pass transistors Q701 and Q702.
collector supplies (figure 2-10) provide the rf head with
the helix and collector voltages required by the BWO.
(b) Pass transistors Q701 and Q702 control the
The helix and collector supplies comprise voltage
amplitude of the input to the highvoltage circuits. The
regulator circuits, highvoltage circuits, and sweep
reference voltage output of the shaper network in the rf
generator circuits. The highvoltage circuits consist of a
head serves as the control voltage which determines the
12kHz oscillator, chopper, bridge rectifier, highvoltage
final value of the dc voltage which feeds the highvoltage
filter, highvoltage monitor, constant current load, resistive
circuits. Sweep voltages, summed with the reference
load, and beta network. Associated with the highvoltage
voltage output, provide the sweep capability of the BWO.
circuits is the shaper network, which is physically located
MODE switch S103 is used to select either the output of
within the re head. The following discussion covers each
the internal sweep generator, an external sweep source,
major section, with unusual circuits described individually
or no sweep (CW). In either mode of operation the
in greater detail.
reference voltage is applied via the regulator error
(1) Voltage regulator circuits.
amplifier circuit consisting of transistors Q508, Q509,
(a) After completion of the 90second warmup
Q511, Q513, and Q515. These stages, described in
greater detail in paragraph (4) below, essentially amplify
period (figure 2-6), 40 volts is made available at the input
and isolate the reference voltage signal. The highvoltage
to the preregulator. Zener diode VR711 and transistor
monitor prevents the output of the regulator from
Q708 (figure 2-10) connected as an emitter follower,
exceeding a predetermined value. As a result, the
compare the input and output voltages of pass
output of the regulator error amplifier controls the
transistors Q701 and Q702. If the voltage difference
maximum limit of the dc voltage applied to the
across these transistors increases to a damaging level,
highvoltage circuits. In addition, a voltage component
the overvoltage appears as a control signal at the base
representing any
of pass transistor Q709.
The collector to emitter
2-11
