Sea Tel USAT User manual

Field Service Procedure – Replacement Pol Pot Kit, USAT
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Document No
135929 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potontheUSATseriesantennas.
2. Checklist:

VerifyRangeofMotion
VerifyPotFeedback
MeasureResistance
3. TheoryofOperation:
Apolangpotentiometerisusedtoprovideafeedbackreferenceforthepositionofthefeedassemblyforlinear
polarization.Thepotactsasapotentialdividergivinganoutputvoltagewhichvariesfrom0VDCto5VDCthroughoutthe
feedassembly’s180degreerangeofmotion.ThePCUconvertsthevoltageoutputfromthepotintothenumericalvalue
displayedontheDAC.Afailurewiththepotcausingittooutputanincorrectvoltagewillresultinthefeedassemblynot
beingalignedcorrectlycausingbadcrosspolisolation.
Oneindicationthatthereisafaultwiththefeedalignmentofthesystemisthatthetargetlightwillbepermanently
illuminatedontheDACandtheantennawon’ttargetcorrectly.Itwillsit8degreesabovethesatelliteselevationlook
angle.Aspartoftheantennastargetingprocedurethesystemwilltarget8degreesabovethesatellite,calculatetheauto
thresholdsettingbasedonthenoisefloorlevelandthenalignthefeedforthecorrectreceptionpositionbasedonthe
vesselsGPSlocationandthelookuptableintheDAC.Ifthesystemisunabletodrivethepolmotortoobtainthecorrect
feedback,orifthepothasfailedandwon’tgivethecorrectfeedback,theantennacan’tcompletethetargetprocessand
theantennawillstayinthisposition.Settingthepoltypeto“0009”willmaketheantennatargetbyremovingtheauto
polfunctionfromthetargetingprocess;howeverthemissalignmentofthefeedwillcausebadcrosspolisolation.
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inthesetupmenuoftheDACto“0009”tosetthemodeofthepolassemblytomanual.
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thefeeddoesn’thavethefull180degreesofrotationverifytheresistanceofthepotasperthefollowingprocedure.
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Field Service Procedure – Replacement Pol Pot Kit, USAT
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consent of Sea Tel, Inc. 
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5. VerifytheResistanceofthePolPot:
Thepolangpotentiometer(polpot)consistsofaninternalslideraswellasaclockwiseandCcounter‐clockwisecontact.
Toverifytheresistanceofthepotamulti‐metercanbeusedtomeasurebetweenthesliderandoneofthewiperswhile
rotatingtheshaftthroughitsrangeandverifyingthe0–5ohmsisoutputtedcorrectly.Disconnectthepot’sreflector
harnessconnectorfromthepolpotsconnection.
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Lookingdownontotheshaftofthepotrotateitclockwiseuntilit
reachesitsendstop.
Nowmeasuretheresistancebetweenthesliderandthecounter‐
clockwisecontact(greycable,pin2andtheredcable,pin3).
Thefeedbackshouldbeapproximately5kohms.

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Nowslowlyrotatetheshaftofthepotcounterclockwise,the
readingshouldcountdownsequentially.Afteroneandahalfturns
thepotwillbeinthecenterofitsrangegivingaresistanceof
approximately2.5kohms.

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Continuetorotatethepotuntilthecounterclockwiseendstop(it
willnowhaveturnedthroughall3rotationsofitsrange),the
resistanceshouldbeapproximately0ohms.
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Leavingthepotatitscounterclockwiseendstopmeasurebetweentheclockwisecontactandtheslider(thegreycable
pin2andtheblackcablepin1).Theresistanceshouldbereversedfromthepreviousrotation,reading5ohms.Rotating
theshaftofthepotclockwiseshouldreducetheresistancethroughitsrangeto0ohms.
Anyerrorwiththepotnotgivingthecorrectresistanceisanindicationthepotisdefectiveandneedsreplacing.
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Field Service Procedure – Replacement Pol Pot Kit, USAT
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135929 Rev A
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Tel, Inc. This document may not be reproduced or distributed in any form without prior written
consent of Sea Tel, Inc. 
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6. ReplacingthePolPotAssembly:
6.1. Tools.

9/64”AllenWrench/Key
12mmWrench/Spanner
1/16”Wrench/Spanner
Loctite222,242and638
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6.2. Procedure.
Procedureforreplacingthepolpot,SeaTelkitpartnumber:134918(polpotpartnumber:128915‐1).

*Caution:Powerdownthepedestalbeforefollowingthis
procedure.
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1.Disconnectthereflectorharnessconnectorfromthepol
potconnectionandthencompresstheretainingclipsto
removethepolpotconnectorfromitsmountingbracket.



2.Locatethepolpotonthefeedassemblyandremoveit
usinga9/64”Allenwrench.Thepotissecuredviaasingle
screw,washerandstarwasher,savethehardwareforfuture
use.

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3.Nowusingthepartssuppliedinthekitbuildupthe
replacementpolpotassembly.Firstinstallthebrackettothe
potandsecurethenutusinga12mmwrench.
*Note:Theorientationofthebracketandthepositionit’s
installedin,inrelationtothepolpotscables.
4.Nowinstallthepulley,applyingLoctite638totheshaft.
ApplyLoctite222tothesetscrewsandtightenusinga1/16”
Allenwrench.Usethedefectivepotasareferencetoensure
thepulleyisinstalledinthecorrectposition.
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Field Service Procedure – Replacement Pol Pot Kit, USAT
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consent of Sea Tel, Inc. 
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
5.Therotationofthepolpotconsistsof3complete
revolutions.Wheninstallingthepotit’sgoodpracticetoset
itinthecenterofitsrange(1.5turnsfromoneofitsend
stops)whilealigningthefeedinthecentreofitsrange(so
thattheLNBishorizontalwiththecoaxcablepointing
towardstheleft).
Thismeansthecalibrationofthepotwillonlyrequire
minimaladjustmentandpreventdamagetotheassemblyby
allowingittodriveintooneofitsmechanicalendstops
(whichispossibleifthereisalargeamountoferrorinthepot
alignment).
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6.Installthereplacementpotassemblyontothefeedby
loopingthepulleythroughthebelt.Theninstalltheflat
washer,followedbythestarwasherontotheretainingscrew
andapplyLoctite242tothethread.Pulldownonthe
assemblytotensionthebeltandtightentheretainingscrew.

*Note:Additionalmountinghardwareisprovidedinthekit
shoulditberequired.



7.Verifythetensionofthebeltbypressingonitatthe
centralpositionbetweenthepolpot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.


8.Installthepolpotsharnessconnectionintoitsmounting
pointandconnectthereflectorharnesstothepolpot
connector.
9.Refertothefollowingcalibrationproceduretoalignthe
potentiometer.

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Field Service Procedure – Replacement Pol Pot Kit, USAT
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consent of Sea Tel, Inc. 
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7. PolPotAlignmentandVerification:

*Note:DonottrytodrivethepolarityoftheantennausingthepolwindowoftheDAC,remotecommandsmustbe
used.

1. DrivethereflectortozerodegreesofelevationtoviewtheorientationoftheLNB:
Pressthebuttontoturnthetrackingfunctionoff(ifapplicable)topreventtheantennafromgoingintoa
search.Pushthebuttonuntilthe“Antenna”windowisdisplayed(thescreenwillshowtheAZ,ELandREL
values).Pressthebuttontwicetoisolatethe“EL”windowandthenpressthearrowtoactivateit(a
cursorwillbedisplayed).Nowusetheandarrowkeystoscrollthecursoralongandusetheandarrow
keystochangetheelevationvalueto“00.0”andpressthebutton.

2. SetthePolTypetomanualmode:
Enterthe“SetupMenu”modebypressingandholdingthearrowkeystogetheruntilthe“ELTrim”or
“AutoTrim”windowisdisplayed.Pushthearrowkeyuntilthe“PolangType”windowisdisplayed.Pressthe
arrowkeytoactivatethewindow.Nowusetheandarrowkeystoscrollthecursoralongandusetheand
arrowkeystochangethecharacters.Setthe“PolangType”to“0009”whichismanualmodeandpressthe
button.

3. Pressthebuttonagaintodisplaythe“PolOffset”window.Verifythepoloffsetissetto“0030”,ifnotpress
thearrowkeytoactivatethewindow.Nowusetheandarrowkeystoscrollthecursoralongandusethe
andarrowkeystochangethecharactersto“0030”andpressthebutton.
4. Nowpressthebuttonagaintodisplaythe“PolScale”window.Verifythepolscaleissetto“0090”,ifnot
pressthearrowkeytoactivatethewindow.Nowusetheandarrowkeystoscrollthecursoralongand
usetheandarrowkeystochangethecharactersto“0030”andpressthebutton.
4
*Note:Ifthepoloffsetwassettoanothervalueotherthan“0090”thefeedwon’thavethefull180degreesof
rotationwhichwouldhavecausedalignmentissues.Ifthiswasthecasesetthepolscaleto‘0090’andrepeatthe
“verifytherangeofmotion”testatthebeginningofthisprocedure.

5. Nowkeeppressingthebuttonuntilthe“RemoteCommand”windowisdisplayedandpressthearrowkey
toactivatethewindow.Nowusetheandarrowkeystoscrollalongandtheorarrowkeystochange
thecharacterstoread“g0120”andpressthebuttontosendthecommandtodrivethefeedassemblytothe
centerofitsrange.
*Note:It’sadvisabletohavesomeonewatchingthefeedwhileit’sbeingdrivenasifthepotisn’tcorrectly
calibratedthereisthepossibilitytodamagethemotorifthefeedassemblyhitsitsmechanicalendstop.

(Steps6‐11requireassistancetoobserveandoperateantennasimultaneously)

6. ObservethephysicalalignmentoftheLNB:
TheLNBshouldbealignedhorizontallywiththecoaxcablepointingtotheleft(asshownbelowinFig.1.1).Ifnot
continueontostep7,otherwiseskipaheadtostep11.

Field Service Procedure – Replacement Pol Pot Kit, USAT
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consent of Sea Tel, Inc. 
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*Note:AlevelbubbleorspiritlevelcanbeplacedontheLNBtoverifytheaccuracyofitsalignment.


(Fig:1.1)

7. IftheLNBisn’thorizontalatthecentralpositionofthepotsrange(120counts)theLNBwillthenneedtobe
physicallydrivenuntilitisalignedhorizontallyandthenadjustmentswillneedtobemadetothepositionofthepol
pottocalibrateitforavalueof120counts.TodrivetheLNBtohorizontalenterdrivecommandsintotheremote
commandscreenoftheDACtorotatethefeedassemblybyissuingdrivetothepolmotor:
ForexampleiftheLNBisovertotheleftofcenterandneedstobedrivenclockwisetobringittohorizontalincrease
thepolvalue.Enter“g0130”,“g0135”,g0137”andsoonintotheremotecommandscreenuntiltheLNBisaligned
horizontally.
ShouldtheLNBbeovertotherightofcenterandneedstobedrivencounter‐clockwisetobringittohorizontal
decreasethepolvalue.Enter“g0110”,“g0105”,g0103”andsoonintotheremotecommandscreenuntiltheLNBis
alignedhorizontally.

8. OncetheLNBhasbeenalignedhorizontally(asperFig1.1)locatethepolpotonthefeedassemblyandloosenthe
retainingscrewusinga9/64”Allenwrench(asshownbelowinFig.1.2).
Slidethepolpotsbrackettowardsthefeedassemblytoslackenthebelttensionandallowthepolpot’spulleytobe
rotated(asshownbelowinFig.1.3).Adjustthepolpotasnecessary:
IftheLNBistotheleftofcenter(needstoberotatedclockwisetobringittolevel)rotatethepulleycounter‐
clockwise.IftheLNBistotherightofcenter(needstoberotatedcounter‐clockwisetobringittolevel)rotatethe
pulleyclockwise.


(Fig.1.2)(Fig.1.3)

9. Resendtheremotecommand“g0120”tore‐centerthefeed,youmayfinditeasiertodrivethefeedawayfromits
centralpositionandthenbacktocenter(I.e.sendthecommand“g0130”followedby“g0120”).


Field Service Procedure – Replacement Pol Pot Kit, USAT
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10. VerifyiftheLNBishorizontalinthecenterofthepotsrange(120counts),iftheLNBisnothorizontal(asperFig.1.1)
repeatsteps7‐9untilcorrect,otherwisemoveontostep11.
*Note:Thetoleranceforcalibrationofthepolpotis+/‐2degrees,meaningtheLNBcanbealigned+/‐2degrees
fromhorizontalatapolcountof120.Anyerrorwillbeelectronicallytrimmedusingthepoloffsetfunction.

11. Nowthepotiscorrectlyalignedverifyfeedhasthecomplete180degreerangeofmotionbydrivingtheassembly
fromendstoptoendstop:
Enterthecommand“g0020”intotheremotecommandscreenoftheDAC.Thiswilldrivethefeedassemblytoits
lowerelectronicendstop(setbythepotentiometer).OncethepolmotorhasfinisheddrivingtheLNBshouldbe
vertical,totheleftoftheOMTwiththecoaxcablepointingdownwardsasshownbelowinFig.1.4.
Nowenterthecommand“g0210”intotheremotecommandscreenoftheDAC.Thiswilldrivethefeedassemblyto
itsupperelectronicendstop(setbythepotentiometer).OncethepolmotorhasfinisheddrivingtheLNBshouldbe
vertical,totherightoftheOMTwiththecoaxcablepointingupwardsasshownbelowinFig.1.5.


(Fig.1.4)(Fig1.5)

12. SetthePolTypetoautomatic(autopol):
Pressandholdthearrowkeystogetheruntilthe“ELTrim”or“AutoTrim”windowisdisplayed.Pushthe
arrowkeytoscrollthroughthesettingsuntilthe“PolangType”windowisdisplayedandpressthearrowkey
toactivatethewindow.Nowusetheandarrowkeystoscrollthecursoralongandusetheandarrow
keystochangethevaluefrom“0009”to“0072”andthenpressthebuttontoputthesystembackinto
automaticpolang(autopol)mode.
WatchtheLNBandverifyitreturnstothecorrectreceptionposition(whilethepolmotorisdrivingthetargetlight
willbeilluminatedontheDAC).
*Note:IfmakingadjustmentstothepolarizationalignmentofaVSATantennacontactingtheNOCafterwardsto
runthroughacross‐polisolationtestandcalibratingtheantennaspoloffsetsettingwillbenecessary.

13. SavethesettingsintheDAC‐2202:
Pressandholdthearrowkeystogetherbriefly,“SaveNewParameters”willbedisplayed.Pressthe
arrowkeytoactivatethewindowandthenpressthebutton,“ParametersSaved”willbedisplayedandthe
poltypeandpoloffsetwillbestoredintheDAC.