Field Service Procedure – Replacement PCU Kit, ST88, ST94 & ST144
Page
1
of
22
Document No
137738 Rev A
Copyright © Sea Tel, Inc 2012 - The information contained in this document is proprietary to Sea
Tel, Inc. This document may not be reproduced or distributed in any form without prior written
consent of Sea Tel, Inc.
1.
Brief
Summary:
Troubleshooting
document
for
diagnosing
a
fault
with
and
replacing
the
PCU
assembly
on
the
ST88,
ST94
and
ST144
antennas.
2.
Checklist:
Verify
Initialization
Measure
the
Power
Supply
Input
/
Output
Voltages
PCU
Status
Pedestal
Error
Verify
Stabilization
Verify
Targeting
Test
for
Azimuth
Drift
Verify
the
Communications
Path
Test
Pol
Drive
3.
Theory
of
Operation:
The
MK2
PCU
assembly
contains
the
24VDC
pedestal
power
supply
(kit:
135341),
PCU
motherboard
PCB
(kit:
135338),
motion
platform
PCB
(kit:
135342)
and
above
decks
400MHz
modem
PCB
(kit:
135349).
The
PCU
motherboard
calculates
the
amount
of
movement
from
the
vessel
based
on
the
feedback
from
the
sensors
on
the
motion
platform
PCB
and
directional
changes
from
the
vessels
gyro
compass
which
are
fed
into
the
control
loop.
It
then
sends
the
command
to
the
MDE
enclosure
to
drive
the
relevant
axis
by
an
equal
and
opposite
amount
of
movement
to
maintain
stabilization
and
control
the
antennas
dishscan
pattern.
The
PCU
software
configures
the
function
of
the
pedestal
and
is
calibrated
by
the
N0
parameter
which
sets
the
motor
gains
for
the
size
of
the
antenna
as
well
as
configuring
the
dishscan
pattern.
The
MK2
XX09
PCU
Motherboard
PCB
features
an
integrated
Pol
Aux
relay
PCB
as
well
as
status
LEDs
for
diagnostic
purposes;
a
Mini
USB
port
for
software
uploads
and
service
serial
port
for
Bluetooth
connection.
The
motion
platform
PCB
houses
5
sensors.
Two
solid
state
MEM
sensors
which
are
used
as
the
antennas
horizon
reference
(level
position)
and
long
term
stabilization
reference,
and
3
solid
state
rate
sensors,
one
for
each
axis,
which
are
used
for
short
term
stabilization
reference.
A
faulty
sensor
on
the
motion
platform
PCB
will
cause
the
antenna
to
lose
stability
and
mispoint
from
the
satellite
under
dynamic
conditions;
however
the
system
may
appear
to
be
operational
in
the
port
when
there
is
no
motion
to
counteract.
RS
‐
422
Pedestal
communications
from
the
DAC
‐
2202
are
modulated
into
a
frequency
by
the
base
400MHz
modem
and
diplexed
with
the
L
‐
Band
receive
signal.
The
communications
frequency
will
then
be
demodulated
by
the
pedestal
400MHz
modem
and
converted
back
into
RS
‐
422
before
being
sent
to
the
PCU.
Radio
MandC
signals
(RS
‐
232,
RS
‐
422,
or
RS
‐
485)
can
also
be
multiplexed
along
with
the
pedestal
communications
to
interface
with
the
SSPB.
The
150W,
24VDC
power
supply
is
switch
mode
and
will
convert
either
110VAC
or
220VAC
into
24VDC.
This
component
is
universally
used
in
the
DAC
‐
2202,
XX97
and
XX06
pedestal
power
supplies
as
well
as
the
XX09
and
XX10
PCU’s
and
NJRC
24V
BUC
power
supplies,
meaning
only
a
single
unit
is
needed
as
a
spare
to
cover
a
wide
range
of
applications.
Summary of Contents for ST144
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