Specifications

Section-5 Maintenance
October 17, 2013
5‐34
Copyright©2013,HarrisBroadcast
WARNING:Disconnectprimarypower priortoservicing. 888‐2693‐004
STEP 17 Verifythataforwardpowersamplefromtheafterthefinalamplifierbut
beforethefilterisconnectedtothePOST‐FILTERportonthebackofthe
LPU.Thermslevelofthesampleshouldideallybeapproximately‐5dBm.
STEP 18 Verifythattransmitteroutputisconnectedtoaquality50ohmload.
STEP 19 VerifythatthelinearRTACmodeissettoBYP ASS.
STEP 20 Applytheappropriateinternalcustomvideotestpatternspecifiedfor
calculatinglinearcorrection.SetRegModetomanualanddoubleclickon
patterntoverifypatternactivationonspectrumanalyzer.
a.
ForNTSC,useNTSCpattern
b. ForallPAL,useSystemD/Kpattern
STEP 21
Verifythatthepost‐filtersamplelevelisslightlybelowtheblacklineonthe
RTACstatusscreen.
STEP 22 VerifywiththespectrumanalyzerthatthesoundcarrierisswitchedON.
STEP 23 Setsyncleveloffsettoachieve40IRE(NTSC)or300mV(PAL)asnecessary.
STEP 24 SetthelinearRTACmodetoADAPT.
STEP 25 VerifythatthelinearRTACattemptandsuccesscountersincrementto1and
1.
STEP 26 Afteroneortwoadaptations,switchtheRTAClinearmodetoHOLD.
STEP 27 WiththelinearRTACmodesettoHOLD,thelinearequalizationhasbeen
calculatedandappliedtothesignal.Rechecksynclevelwithblackpicture
(nosetup).Adjustifnecessaryfor300mVPALor40IRENTSClevels.
VerifyingLinearEqualizer:
STEP 28
Measuretheamplitudeandgroupdelayresponseacrossthechannel.
STEP 29 WiththelinearRTACinHOLDandthenonlinearRTACinHOLDorSTORED,all
correctionhasbeencalculatedandappliedtothesignal.
STEP 30 PerformtheprocedureinSection5.7.2onpage5‐35tostorethecurrent
correction.Pla
ceLinearandnon‐linearRTACmodestoSTORED.
STEP 31 Proce dur ecomplete.
5.7.1.1 TroubleshootingPrecorrection
IftheRTACmodeissettoADAPT,buttheAttemptscounterdoesnotincrementwithinthirtyseconds,thereisa
problemwiththefeedback.
Checkthesignallev
elsatthePREandPOST‐FILTERinputsonthebackoftheLPU.Theyshouldbebetween‐10dBm
and+5dBm(optimumis0dBmattheinputsonthebackoftheLPU).
ChecktheRT
AClevelsontheSTATUS>RTACGUILPUscreen.Thebarmetersshouldbegreenandthelevelshould
bejustbelowtheblack100%line.
Checktha
ttheexciterHomeScreenshowsONintheupperleftcorneroftheGUIscreen.IftheexciterisOFFor
MUTE,thecorrectionscannotbecalculated.