Western Electric 407A-4, Instruction Manual

Page: 12 / 136

transmission l ine to the antenna-coupling unit, and the
coaxial harmonic shunt line , connect d irectly to the output
terminals of this power amplifier.
D-99116 Control Unit The maj or ele­
ments of the control system which suppl ies power in the
proper sequence to the various parts of the equipment, to­
gether with the s ignal lamps and their ass oc iated relays ,
are locate d in this unit .
in 50 kw Enclosure
D-99119
Rectifier Tube Unit In
this unit are mounted s even 255B mercur y-vapor rectifier
tubes
(
one a spare tube ready fo r quick connecti on
)
with
the ir arc-back re lays and air blower. The grounding switch
as s oc iated with the main enclosure gate is als o a part of
this as s embly.
D-99120 Grid-Bias Rectifier This unit sup­
pl ies b ias to the modulating amplifier and power amplifier.
Special D-9 9 775 Condens er and Switch
This as semb ly includes the high-voltage fi lter condens ers ,
its charging resistor and ass ociated contactor, and two cur­
rent-limiting resistors .
Filter Choke Coil
This choke
coil, together with the main filter condens er, forms the
plate-supply filter for the two water-cooled stages . A
Thyrite Surge Protector
(
PR52P
)
is associate d with the
choke coil to prevent the building up of excessive voltages
in the event of sudden overloads .
Equipment in 5-kw Enclos ure
Special D- 99114 Rectifier This rectifier
provides plate and grid-bias supplies for Unit C, for emer­
gency operation at 5-kw. It includes s even 315A me rcury
vapor rectifier tubes
(
one a spare tube ready for quick
5