Western Electric 407A-4, Instruction Manual

Page: 78 / 136

Filaments
Close the switch "Ampl ifier Filaments "
(
D3F
)
which en­
ergizes S 53P supplying power to the mo dulating ampl ifier
filaments , and S58P supplying power to the amplifier fila­
ments through the starting res istors R51-53P . After a delay
of a few seconds S6 3P operates , energiz ing S 59P which shorts
R51-53P and applies full voltage to the fi laments .
High-Voltage Control
At the s ame time that the bias rectifiers are energi zed,
the c ontrol circuit is complete to the high-voltage control
of the oscillator-amplifier unit . With the switch "Plate
Rectifier"
(
D4A
)
in the "ON" pos ition, the green lamp above
the switch '10s c illator-Amplifier Plate Voltage"
(
D5F
)
light s .
Throw this switch to 110N11 operating S 3A and energizing the
plate rectifier of the oscillator-amplifier unit .
As s oon as all amplifier filaments and b ias rectifiers
have been energiz ed and i f link switch D30C is in the D30. 1C
pos iti on, the c ontrol circu it of the high-voltage rectifier
for the power amplifier is completed and the green light
above the switch "High-Voltage Rectifi er11
(
D4F
)
lights .
With the switch "Plate-Voltage Regulator 11
(
D8F
)
and
the "Automatic-Manual " switch on the regulator
(
T 56P
)
both
clo s e d to "Automatic'·• the green light "Plate-Voltage Regu­
lator-Minimum"
(
E28F
)
lights .
Close the switch "High-Voltage Rectifier"
(
D4F ) en­
ergizing the closing cir cuit for the plate cir cuit b reaker .
The lamp "H.V . Rect. Circuit Breaker - Open"
(
E26F
)
lights .
As soon as the breaker is closed the lamp is extinguished
and the lamp 11 Closed11 (E27F
)
lights . The rectifi er is en­
ergiz ed and the meter "Power Amp . Plate 11 (M7F
)
should read
about 14
kV .
The plate regulator imme diately starts in­
creas ing the voltage to 18-kv and then holds it at that
value . The "Lamp Reset "
(
K3F
)
should b e pushe d to light
71