Section-4 Theory
October 28, 2013
4
‐
10
Copyright
©2013,
Harris
Broadcast
WARNING:
Disconnect
primary
power
prior
to
servicing.
888
‐
2720
‐
001
The
AC
Mains
connect
to
the
board
which
feeds
the
AC
into
each
power
supply
module.
The
power
supplies
are
single
phase
input
and
operate
from
190
to
300
VAC,
50
or
60
Hz.
The
AC
service
connected
to
the
FAX
must
have
a
Line
to
Line
voltage
or
Line
to
Neutral
voltage
that
falls
within
this
range.
The
AC
service
into
the
transmitter
or
AC
distribution
panel
in
the
rack
can
be
single
phase,
3
‐
Phase
Delta
or
3
‐
Phase
Wye.
There
is
an
AC
Mains
Monitor
circuit
that
monitors
for
low
voltage
only.
The
approximate
trip
point
is
just
below
190
VAC
which
produces
a
fault
but
no
action
is
taken,
the
transmitter
will
stay
on
the
air.
The
transmitter
will
continue
operate
when
1
or
2
phases
are
lost
but
at
a
much
reduced
power.
In
the
power
block
the
supplies
are
distributed
across
the
phases.
Control
signal
PA
ON/OFF
from
the
System
Interface
Controller,
named
PS_ON
on
PS
Interface
board,
feed
each
power
supply
to
turn
its
DC
output
ON
or
OFF.
The
DC
output
can
be
in
the
range
from
+44
VDC
to
+52
VDC
to
accommodate
different
modes
of
transmitter
operation.
There
is
a
+VDC
output
from
each
of
the
7
supplies
to
feed
7
PA
Modules.
Each
PA
has
a
dedicated
Power
Supply
Module.
If
a
Power
Supply
Module
fails,
the
associated
PA
Module
will
shut
off.
This
configuration
allows
for
multiple
failures
while
the
remaining
supplies
keep
the
transmitter
on
the
air
at
a
reduced
power
level.
The
+VDC
for
the
IPA
comes
from
a
diode
controlled
sharing
circuit
that
connects
to
each
of
the
PS
+VDC
lines.
Because
of
the
power
supply
module
sharing,
multiple
supply
failures
will
not
affect
the
IPA
+VDC.
The
IPA
has
an
in
‐
line
fuse
F10
(15
Amp)
on
board.
In
the
Normal
Control
mode
+VDC
output
is
controlled
via
RS485,
if
in
Backup
Control
the
power
supply
voltage
will
change
by
approximately
2
V
when
switched
between
Class
C
and
Class
AB.
There
must
be
at
least
two
functioning
power
supplies
for
the
transmitter
to
remain
operating.
There
is
an
auxiliary
+5
VDC
output
from
each
supply.
This
supply
is
the
main
5
Volts
that
feeds
the
control
circuitry.
There
are
no
other
power
supplies
in
the
system.
Any
other
voltages
on
any
of
the
boards
in
the
transmitter
are
regulated
from
the
5
Volts.
In
the
case
of
FAX
models
with
multiple
power
blocks,
the
+5
VDC
from
each
is
diode
gated
back
to
the
main
power
block.
If
the
AC
fails
to
the
main
power
block
which
houses
the
Multi
‐
Unit
controller
the
transmitter
will
remain
on
the
air
using
5
Volts
control
voltage
from
the
other
power
blocks.
The
Airflow
is
measured
by
comparing
two
LM50B
temperature
sensors,
one
a
heated
reference
sensor
the
other
in
direct
path
of
airflow.
When
the
airflow
in
the
transmitter
drops
the
sensor
in
the
airflow
path
will
increase
in
temperature
and
its
output
will
trip
U2
‐
7
causing
the
transmitter
to
shut
off.
Once
airflow
returns
the
transmitter
will
automatically
turn
back
on.
Dipswitch
S1
serves
2
functions,
sections
1
and
2
are
used
to
set
the
AIRFLOW
fault
trip
level.
Switches
4,
5,
6,
and
7
are
used
to
disable
Power
Supply
Modules
4,
5,
6,
and
7
in
the
FAX
5
transmitter
as
it
only
uses
4
Power
Supply
Modules.
In
the
10kW
Power
Blocks,
the
are
set
in
the
OPEN
(OFF)
position.
Power
for
the
Fans
also
is
provided
by
the
Power
Supply
Module’s
sharing
circuit.
The
shared
PA
Volts
feed
fuse
F9
(15
Amp)
then
to
the
Fan
Control
Board.
4.1.9
Fan Control Board Description
The
Figure
4
‐
11
shows
the
Fan
Monitor
board.
The
Fan
Control
board
monitors
each
fans
tach,
controls
the
speed
of
the
fans
and
also
has
a
RF
power
detector
when
used
on
a
reject
load.
The
cooling
fans
in
the
system
are
variable
speed
and
run
at
a
reduced
speed
under
normal
operating
conditions.
When
certain
faults
occur,
such
as
a
PA
fault,
the
controller
ramps
all
fans
in
the
system
to
full
speed.
This
would
include
the
reject
load
in
the
FAX20/30/40
transmitters.
If
a
fans
tach
drops
below
a
preset
hardware
limit,
the
board
reports
a
fault
back
to
the
FAX
main
controller.
The
fault
also
lights
a
corresponding
LED
that
can
be
seen
on
board
at
the
rear
door
of
the
transmitter.
The
RF
detector
and
temperature
sensor
are
used
when
the
board
is
mounted
on
a
reject
load.
The
RF
sample
from
the
reject
load
is
detected
and
a
DC
voltage
sent
back
to
the
controller.
This
sample
is
calibrated
to
100%
when
an
entire
power
block
is
off
or
an
entire
cabinet
depending
on
the
system.
The
temperature
sample
detects
the
reject
load
temp
and
is
sent
back
to
the
controller.
If
either
temp
or
RF
exceed
a
preset
limit,
a
reject
load
fault
is
generated
and
the
transmitter
will
increase
fan
speed
to
100%
and
reduce
the
transmitter
power
to
25%
to
protect
itself.
Содержание Flexiva FAX 5KW
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Страница 10: ...WARNING Disconnect primary power prior to servicing...
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