unit is removed from the main unit, inter-
inserted in the signal path. In the 20 posi-
t i o n , the -150-volt output of the power
l o c k switch S711 opens and the ac input
supply has a path of continuity to one of
p o w e r path is interrupted from the re-
t h e two relays in the if. step attenuator.
m a i n d e r of the circuitry. The closed con-
W h e n energized, this relay inserts a 10-
dition of interlock switch S711, or the use
d b resistive pad in the if. signal path.
of the alignment harness, permits ac
However, in the 40, 60, and 80 positions
power to flow through vibrating-type reg-
of S701, the -150-volt output of the power
u l a t o r K703 into the primary windings,
supply also has a path of continuity to the
t e r m i n a l s 1 and 2, of power transformer
s e c o n d relay in the if. step attenuator.
T 7 0 2 . One secondary winding, terminals
When both relays in the if. attenuator
1 7 and 18, steps down the 115-volt ac
a s s e m b l y are energized, a total network
input to 6.3-volts ac output, which is used
r e s u l t i n g in 20-db of attenuation is in-
as heater power by all electron tubes
serted in the if. signal path.
except audio amplifier V701 and the stages
h o u s e d in the detector and electrometer
c. Meter Sensitivity Circuit. The 0 CW
a s s e m b l y . A n o t h e r secondary winding,
ONLY position of the SIGNAL ATTENU-
terminals 14 and 16, steps down the 115-
A T O R DB control inserts a 50-ohm re-
v o l t ac input to 5.8-volts ac. This power
s i s t i v e termination in the rf signal path
is used in the heater circuit of audio
a m p l i f i e r V701 and detectors V1 and V2
t h i s termination produces a 10-db loss in
i n the electrometer assembly.
r f signal amplitude, wafer switch S701
b. +150 Volt Unregulated Power Circuit.
( f r o n t ) removes a multiplier resistor from
The 115-volt ac power at the primary of
the dc metering signal path. The value of
power transformer T702 is stepped up
t h i s multiplier resistor is equivalent to a
i n voltage through a center-tapped sec-
10-db gain in meter sensitivity; the meter
o n d a r y winding, terminals 3, 4, and 5.
full-scale indication is effectively changed
Parallel-connected rectifiers V704 and
f r o m 10 microvolt to 1 microvolt. There-
V705 produce a dc output of approximately
f o r e , with 10-db of attenuation inserted
+175-volts with respect to chassis ground.
in the rf signal path, the overall result is
This output is filtered and dropped in value
zero attenuation in the combined rf and dc
by the double L-type filter, which consists
m e t e r signal path.
o f reactor L722 and capacitor C734, and
is used as 150-volt B+ power for all stages
13, Block Diagram of Power Supply
e x c e p t the local oscillators in the tuning
u n i t s and all tubes in the detector and
T h e power supply provides all of the
electrometer circuit. The dc output of
power requirements for the circuits in
V 7 0 4 - V 7 0 5 is also used as a reference
t h e main unit and in the tuning unit. A
voltage for vibrating-type regulator K703.
simplified representation of the power
T h i s reference voltage is applied to the
s u p p l y is shown in the shunt calibration
coil of the vibrating-type regulator, which
a p p l i e s varying amounts of resistance in
power and the development of low-voltage
series with the ac input power, depending
a l t e r n a t i n g current (ac) and rectified dc
on input line fluctuations and output load
v o l t a g e s is shown in the detailed block
diagram (fig. 5).
c. +105-Volt Regulated Power Circuit.
a. Ac Input and Output Power. Ac input
The 105-volt regulated output is derived
i s connected to the main unit at POWER
from the 150-volt power supply. This 105-
receptacle J721. The voltage is fed through
v o l t output is regulated by voltage reg-
P O W E R switch S710 to interlock switch
ulator tube V708, and is used as B+ volt-
S711 and protective fuse F701. The inter-
age by the local oscillators in each tuning
lock switch is closed when a tuning unit is
p l u g g e d into the opening provided at the
d. -150- Volt Regulated Power Circuit.
left side of the main unit. When a tuning
Metallic rectifier CR706 is connected to