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Continental Electronics 816R - Power Supplies and Control Circuits; Power Supply Overview; PA Plate and Screen Power Supplies; Power Control Units

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2.
POWER
SUPPLIES
AND
POWER
CONTROL
CIRCUITS
General.
There
are
five
separate
power
supplies
in
the
transmitter.
Three
of
the
five,
the
plate,
screen
and
power
amplifier
bias
power
supplies
provide
voltages
to
the
power
amplifier.
The
IPA
supply,
furnishes
voltage
to
the
IPA
stage.
The
28
V
de
power
supply
provides
power
to
the
control
circuits.
28
V
de
Power
Supply,
P/O
A10.
The
28
V
de
supply
is
a
fully
self-contained
regulated
power
supply
mounted
on
the
inside
of
the
A
10
Panel.
Power
Amplifier
Bias
Power
Supply,
P/O
A10.
The
power
amplifier
bias
power
supply
provides
the
power
amplifier
with
fixed
grid
bias
that
holds
the
tube
near
cutoff
when
no
drive
signal
is
present
on
the
grid.
Single-phase
primary
power
is
applied
through
contactor
A8K1
and
step-up
transformer
T1
to
a
bridge
rectifier
network.
An
L-section
filter
is
formed
by
inductor
LI
and
capacitor
C2.
The
bias
supply
voltage
is
approximately
275
VDC,
depending
upon
line
voltage.
The
power
supply
output
is
applied
to
the
grid
of
the
power
amplifier
through
diode
CR5.
Diode
CR5
blocks
grid
current
flow
through
the
supply
when
the
grid
leak
bias
exceeds
the
fixed
bias.
A
sample
of
the
bias
voltage
is
applied
through
resistor
R3
to
front
panel
meter
A1M1
for
monitoring.
Power
Amplifier
Plate
Supply
The
power
amplifier
plate
power
supply
provides
part
of
the
plate
voltage
to
the
power
amplifier.
Primary
components
of
the
supply
are
transformer
Tl,
3-phase
bridge
rectifier
assembly
Zl,
filter
choke
LI,
and
filter
capacitor
Cl.
A
meter
multiplier
board,
A12A1,
samples
plate
voltage
and
allows
constant
monitoring.
Input
power
to
transformer
Tl
is
controlled
by
SCR
(silicon-controlled
rectifier)
power
control
unit
A9.
This
unit,
connected
as
a
closed
loop
regulator,
maintains
constant
power
output
to
offset
conditions
of
varying
line
voltage.
PA
Screen
Power
Supply.
The
3-phase
regulated
voltage
from
the
power
control
unit
is
applied
through
transformer
T2
to
a
silicon
3-phase
full-wave
bridge
rectifier
assembly
Z2
in
the
power
amplifier
screen
power
supply.
The
output
of
Z2
is
filtered
and
applied
to
the
cathode
circuit
of
the
power
amplifier
at
the
secondary
center
tap
of
filament
transformer
T5.
AC
VOLTAC-E
APPLIED
TO
P
late
ano
SCREEN
TRANSFORMERS
Figure
7,
SCR
Control
IPA
Power
Supply,
P/O
A5.
The
IPA
power
supply
is
a
3-phase
full-wave
type
using
a
single
section
choke
input
filter.
It
nominally
delivers
45
V
de
at
25
amperes
to
its
load.
The
supply
’
s
primary
power
is
switched
through
relay
A5K1
which
is
operated
by
the
9