right branch of the bridge. The sensing bridge
4-2.
Detailed Circuit Functions
circuit in the lower right branch will send a
signal to the control amplifier (controller, mas-
a. The main rectifier unit, the bleeder re-
ter) which, in turn, will adjust the base bias
sister, the series-paralleled passing transis-
of the master passing transistors. The slave
tors (Q1 through Q6), and the load terminals
controller will automatically adjust the base
(with a load resistor attached) form the up-
bias of the slave passing stage.
per branch of a bridge circuit. The auxiliary
power unit transformer secondary (T3) with
es of the bridge as compared to the voltage
diodes CR10 and CR11 form a full-wave recti-
ratio of the left branches of the bridge will
fier with a regulated output. The regulated
adjust the voltage which will appear across
voltage appears between the REMOTE
the load resistance. As in any bridge circuit,
SENSE binding post and the junction of re-
if one branch is held electrically constant, a
sistor R45 and Zerner diode CR12. In series
change in any one of the other branches will
with the negative end of this supply are po-
affect the other two branches.
tentiometers R30 and R31. The circuit con-
tinues to the junction of Zener diode CR4
the load impedance will affect the loop cur-
and resistors R24, R25 and out the top of this
rents in the passing stages as well as in the
bridge circuit at the junction of resistors R21
sensing bridge. The master and slave control
and R22 to the REMOTE SENSE + binding
circuits will adjust the base bias current in
post.
the passing transistors to hold the load volt-
b. The second circuit will form the lower
age constant.
branch of the bridge. The OUTPUT + and
h. A change in the input power level will
the REMOTE SENSE + binding posts (as
likewise affect the voltage ratio in the bridge
well as the OUTPUT -- and the REMOTE
circuit. This change will be sensed the same
SENSE -- binding posts) are strapped lo-
as a load change. The reference rectifier is
cally. With the load impedance applied as
designed to compensate for input power
shown, the load voltage and current will de-
changes; therefore, the output will be held
pend on the electrical ratios in the branches
constant.
of the bridge.
i. There are three independent bias rectifier
c. One of two electrical ratios is established
circuits in the auxiliary power supply. The
by the regulated dc output of the reference
output level of these circuits will change with
rectifier (between R34 to bottom of R30), and
input power changes. By the design of the
by the output of the main rectifier (across
control circuits, these bias voltages will aid in
bleeder resistor R46). A second electrical ra-
the regulating action of the system.
tio is formed by the impedances of the pass-
j. The response of the regulatory circuits
ing transistor stages and by the sensing
is extremely fast. High gain amplification is
bridge (R21 through R25 and CR4) to include
one of the methods which can achieve this ac-
potentiometers R31 and R30.
The voltage
tion together with the normal sensitivity of
across the load resistor can be reduced close
the bridge-type circuits. The sensing bridge
to zero by balancing the bridge circuit.
of the master control amplifier provides in-
d. The rotor shaft of potentiometer R30
puts to the differential amplifiers within the
(in the lower right branch of the bridge) is
master control unit. The master passing stage
ganged to the shaft of variable transformer
impedance, the bridge ratios, and the slave
T1 (in the upper left branch of the bridge).
passing bias will lock the circuit to the new
The applied voltage at the primary of T2 is
impedance level.
not reduced to zero to bring the de output
voltage to zero. There always will be some
k. Troubleshooting of the circuits is per-
voltage ratio between the main rectifier and
formed by conventional methods.
Once a
the regulated reference rectifier.
trouble is isolated to a transistor unit, a quick
e. As potentiometer R30 is changed, there
check of the voltage between base to emitter
will be an impedance change in the lower
will determine the condition of the transistor.
4-2
