Western Electric 407A-4, Instruction Manual

Page: 25 / 136

control circuits which extend throughout the system. This
unit provides independent control of the oscillator ampli­
fier, of the water system and amplifier filament circuits,
and of the rectifier-tube filaments and bias rectifiers.
The high-voltage control is interlocked with these branches.
With this control circuit, preheating of mercury vapor rec­
tifier tube filaments, testing, and servicing of the various
components of the transmitter may be done with ease with­
out sacrificing any protection of the equipment or operat­
ing personnel.
An
unregulated three-phase 460-volt branch circuit fro�
the power-distribution unit supplies power to terminals
168F, 169F and 170F for the control circuit. Line voltmeter
switch D6F permits switching supply voltmeter MlF across any
phase of this supply as well as across any phase of the
regulated 460-vol t supply which is brought in to terminals
165F, 166F and 167F from the rectifier tube unit. Trans­
former TlF connected across one phase of the control cir­
cuit power supply steps the voltage down to 230 volts for
the control_ circuit proper. The center tap of the second­
ary of TlF is grounded. A no-fuse type manual circuit
breaker is in the secondary of TlF for protection and serves
as a disconnect for the complete control circuit. One side
of the 230-volt circuit which may be considered the return
side is connected to terminals 141F to 147F for control
apparatus external to the control unit. The other side of
the 230-volt circuit connects to DlOF, D2F and DlF for the
three major independent branches of the control circuit:
the oscillator-amplifier, the water system and amplifier
filaments, and the rectifier filaments.
Oscillator-Amplifier
Closing DlOF "Oscillator Amplifier Filaments" supplies
18