COBHAM Sea Tel User manual

Field Service Procedure – Replacement Pol Motor Kit, USAT
Page 1 of 7 Document No
136481 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 pol motor on the USAT series antennas.
2. Checklist:
Pedestal Error
Verify Motor Drive
Drive the Pol
Measure Motor Voltage
3. Theory of Operation:
Based on the vessels GPS position and the desired satellite the pol motor will drive the feed assembly to align it
in the correct reception position for the linear satellite signal, then as the vessel sails and the GPS position
changes the pol motor will be driven to maintain the correct reception position as the look angle the satellite
changes.
Under dynamic conditions feedback from the sensors are fed into the PCU where the amount of voltage change
overtime is calculated into the amount of physical movement being exerted on the system and in turn the PCU
will drive the elevation and azimuth axis’s to counteract this motion. While the elevation and azimuth axis’s are
driven the feed will also need to be driven to maintain the correct look angle to the satellite and retain good
cross pol isolation. For added stability a fourth rate sensor is installed on the feed assembly of the USAT to
monitor the stabilization of the feed assembly, offering the performance of a 3 axis pedestal.
4. Verify the Range of Motion:
*Note: Do not try to drive the polarity of the antenna using the pol window of the DAC, remote commands must
be used. Also no update on the pol value will be displayed on the DAC when the pot is rotated; it works solely
from drive commands entered into the remote command screen.
First verify the settings in the DAC are correct, the pol scale should be set to 0090 to give the feed 180 degrees
of motion. The default pol offset setting for a USAT antenna is 0030 (however this may have been modified
slightly to “trim” the pol angle). Turn tracking off (if applicable) and drive the elevation to 0 degrees to make it
easier to view the feed assembly for diagnostic purposes.
Set the pol type setting in the setup menu of the DAC to “0009” to set the system into manual pol mode.
Now enter the remote command window (in the setup menu) and input the command “g0020” to drive the feed
assembly to its lower limit. The LNB should be vertical, to the left of the OMT with the coax cable pointing
downwards.
Now drive the feed to its upper limit by inputting “g0210” into the remote command screen of the DAC. The LNB
should be vertical to the right of the OMT with the coax cable pointing upwards.
If no drive is issued verify if the motor is receiving voltage as per section 8 of this document. If the feed doesn’t
have the correct 180 degrees on motion for the targeted commands this is an indication that the pot is outputting
an incorrect value.

Field Service Procedure – Replacement Pol Motor Kit, USAT
Page 2 of 7 Document No
136481 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.
5. Verify Pot Range:
If no feed drive is present verify the pol reading on the DAC isn’t out of range (i.e. displaying a value of either 0
or 255). If one of these values are displayed it’s possible the pot isn’t aligned correctly and that adjusting it may
bring within its range. Back the pot off from the main gear sprocket and rotate its pulley, then reinstall it and re-
enter one of the pol drive commands into the remote command screen of the DAC.
Re-enter one of the drive commands into the remote command screen of the DAC, if the feed assembly still fails
to move and the pol count doesn’t change then the pot has failed and is outputting a default value. No drive will
be issued to the pol motor as the value is out of the range which the system operates in, therefore the pol pot
must be replaced.
6. Pedestal Error (Error 8):
6.1. Decoding a Pedestal Error.
*Note: A “CL” error on the USAT series antennas relates to the pol axis.
When the DAC displays a pedestal error enter into the remote command window and input “S0000” then
press enter twice. The error code will now be displayed in the Remote Monitor screen. Decode the 4th
character of the error code from the below table...
@ None K Ref + LV + CL V Stab Limit + AZ + LV
A CL L Ref + AZ W Stab Limit + AZ + LV + CL
B LV M Ref + AZ + CL X Stab Limit + Ref
C CL + LV N Ref + AZ + LV Y Stab Limit + Ref + CL
D AZ O Ref + AZ + LV + CL Z Stab Limit + Ref + LV
E AZ + CL P Stab Limit [ Stab Limit + Ref + LV + CL
F AZ + LV Q Stab Limit + CL \ Stab Limit + Ref + AZ
G AZ + LV + CL R Stab Limit + LV ] Stab Limit + Ref + AZ + CL
H Ref S Stab Limit + CL + LV ^ Stab Limit + Ref + AZ + LV
I Ref + CL T Stab Limit + AZ _ Stab Limit + Ref + AZ + LV + CL
J Ref + LV U Stab Limit + AZ + CL

Field Service Procedure – Replacement Pol Motor Kit, USAT
Page 3 of 7 Document No
136481 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.
6.2. Error Types.
The 3 types of pedestal error are:
1. Servo Limit (CL, LV & AZ) –A servo limit error means the PCU motherboard is issuing the
command to the motor driver PCB/servo amp to drive the relevant axis harder than it should
under normal operation (the servo limit has been reached). This could be while the antenna is
trying to maintain its pointing angle, or while the antenna is driving the axis to a target position.
2. Stability Limit – A stability limit error means the antenna has mis-pointed from its desired
target position by more than half a degree. When a stability limit error is flagged on a VSAT
antenna the DAC will send the TX Mute command to inhibit the transmit function of the satellite
modem (It’s common to see the servo limit and stability limit errors together).
3. AZ Reference Error – An azimuth reference error means the there is a corrupt reading in the
relative scale. This could be caused by the encoder failing, a limited azimuth antenna hitting its
end stop under normal operation, an unlimited antenna completing a 360 degree rotation
without the sensor coming into contact with the home flag, the sensor coming into contact with
the home flag too early, or a physical problem such as the belt slipping on the motor pulley.
6.3. Troubleshooting Pedestal Errors – Servo Limit and Stability Limit.
1. Reinitialize the pedestal; does it drive correctly or at all? If none of the axis drive verify the N0 &
motor gain parameters (N1 = CL, N2 = EL & N3 = AZ) are correctly configured in the PCU
through the Remote Command window of the DAC.
2. Verify the balance of the antenna & check for physical restrictions on the pedestal. If the axis
isn’t correctly balanced the PCU will be outputting additional drive commands to maintain the
antennas level position.
3. If the motor isn’t driving correctly or no motor drive is present, test the motor for faults using the
below procedure, if the motor is defective replace it and then retest the function of the antenna.
If the axis still fails to drive correctly the defective motor may have damaged the motor driver
PCB. Replace the PCU assembly.
4. Another potential problem could be a damaged or intermittent harness connection. Remove the
harness back shells and verify all the pins are seated correctly, check continuity from pin to pin
& also across the pins to verify there is no short in the connections.
6.4. Troubleshooting Pedestal Errors – Azimuth Reference Error.
1. Reinitialize the system and verify that the USAT 24 antenna drives clockwise to its end stop or
the USAT 30 drives counter clockwise to its end stop.
2. Drive the azimuth axis in 90 degree increments and verify that the antenna points correctly, and
that the DAC displays the correct relative position. Also verify that there is no physical restriction
on the azimuth axis such as the belt slipping on the motor pulley or the pulley slipping on the
motor shaft.

Field Service Procedure – Replacement Pol Motor Kit, USAT
Page 4 of 7 Document No
136481 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.
7. Test the Pol Motor Drive:
Pol motor drive can be verified by introducing an error into the system which the pol motor will have to
counteract. Remove the radome top and unbolt the pedestal from its mounting point, now if you rock the
antenna from side to side the pol motor will drive the feed assembly to counteract the motion being exerted on
the system.
If it is suspected there is a dead spot in the motor power down the system and gently rotate the axis by moving
the belt backwards and forwards. This in turn will rotate the motor pulley and shaft and it should be apparent if
there is a dead spot as the rotation will feel taught at that position.
*Caution: Be extremely careful rotating the pedestal around while your fingers are in this
area to prevent pinching or crushing your fingers in the pedestal assembly.
8. Measure the Motor Voltage:
If no drive is present verify if the pol motor is receiving the 24VDC from the PCU. Power down the pedestal by
switching off the DAC then disconnect the reflector harness from the pol motor connector and re initialize the
pedestal (a pedestal error will be displayed as the pol axis can’t initialize).
Once initialized you should be able to measure 24VDC should be present between pin 3 and ground (pin 5 or
the harness back shell) and pin 8 and ground (pin 5 or the harness back shell). If the voltage is present and the
motor isn’t driving the motor is defective and needs to be replaced, if the voltage is not present then the PCU
isn’t outputting the voltage and is defective.

Field Service Procedure – Replacement Pol Motor Kit, USAT
Page 5 of 7 Document No
136481 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.
9. Procedure for Replacing the Pol Motor:
9.1. Tools.
#1 Phillips Screwdriver
7/64” Allen Wrench/Key
5/16” Allen Wrench/Key
3/16” Wrench/Spanner
Long-Nose Pliers
Loctite 222, 242, and 638
9.2. Procedure.
Procedure for replacing the pol motor on the USAT series antennas, Sea Tel kit part number: 125266-1
(motor part number: 124700).
*Caution: Power down the pedestal before following this
procedure.
1. Using a #1 Phillips screwdriver remove the two screws
securing the pol harness into the 9-pin connector. Save
the hardware for future use.
2. Disconnect the pol pot connector and remove it from
the mounting bracket.
3. Using a 7/64” Allen wrench remove the screw securing
the harness connector to the polang plate. Save the
hardware for future use.
4. Using a 5/16” Allen wrench remove the 3 sets of
hardware securing the pol motor assembly to the polang
plate. Save the hardware for future use.
5. Remove the defective pol motor assembly.

Field Service Procedure – Replacement Pol Motor Kit, USAT
Page 6 of 7 Document No
136481 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.
6. Using a pair of 3/16” wrenches remove the standoffs
securing the bracket to the defective pol motors D-sub
connector.
7. Install the pulley on the replacement motor in the same
position as on the defective pot assembly. Apply Loctite
638 to the motor shaft and secure the set screw with
Loctite 222 using a 1/16” Allen wrench.
*Note: For further information refer to the Loctite
Procedure 121730 provided with this kit.
8. Install the bracket to the replacement motor assembly
using the hardware removed in step 6.
*Note: The orientation of the connector in relation to the
bracket.
9. Locate the pulley into the belt and install the motor
assembly to the feed using the hardware removed in step
4.n Align the motor with harness exiting downwards, apply
Loctite 242 to the threads, do not fully tighten at this time.
10. Apply downward pressure to the motor to tension the
belt and tighten 2 of the retaining screws.

Field Service Procedure – Replacement Pol Motor Kit, USAT
Page 7 of 7 Document No
136481 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.
11. Verify the tension of the belt by pressing on it at the
central position between the motor pulley and the main
drive sprocket. There should be a little give, but the belt
should be tight enough that the axis will drive correctly,
without skipping on the teeth of the pulley. If the belt is too
tight/loose repeat the previous step until the belt tension is
correct and tighten all three of the screws.
12. Install the pol motor bracket to the feed using the
hardware removed in step 3. Apply Loctite 242 to the
thread.
*Note: Angle the bracket away from the connector to
allow sufficient clearance to connect the
13. Connect the reflector harness D-sub connector to the
motor connection using the hardware removed in step 1.
14. Insert the pol pot connector into the bracket and
connect the reflector harness connection.
15. Secure the pol motor harness to the body of the motor
using a cable tie.