HP-335C-335D-Manual 电路图.pdf

HP Archive This vintage Hewlett Packard document was preserved and distributed by www. Please visit us on the web ! On-line curator: Glenn Robb This document is for FREE distribution only! RadioFans.CN 收音机爱 好者资料库 - INSTRUCTIONANDOPERATINGMANUAL FOR ODELS335c133%at33.3KC. Accuracy- Within5%modulationpercentageoverentirescale. MeterCharacterstic8+- MeterdampedinaccorancewithFCCrequirements.Readspeak valueofmodulationpeakofdurationbetween40and90milli- seconds.Meterreturnsframfullreadingto10%offullvalue within500to800milliseconds. FrequencyResponse- Flatwithinidbfrom50to15000cycles/sec 1 - RadioFans.CN 收音机爱 好者资料库 ExternalMeters- ProvisionsaremadeforinstallationofremotemeterhavingfUll scalesensitivityof400microamperes.Scaleshouldindicate 10Q%modulationat300microamperes.Extrameterscanbesupplied withunit. PeakLimitRange - From50%to120%modulation(25KC100%).Provisionfor externalpeakindicators. FrequencyRange- 50cpsto26KC.Responseflatwithin+idb.Equippedwith Standard75microsecondde-emphasiscircuit. Distortion- Lessthan0.25at100modulationfrom50cycles/secto15kc. OutputVoltage- 10Yo1tsinto20,000ohmsatlowfrequenciesat100%modulation atlowfrequencies. Noise- Atast70dbbelowaudiooutputlevelresultingfrom100% modulationatlowfrequencies. MonltorinOutput- 4mwinto600ohmsbalanced,at100%modulationatlowfre- quencies. PowerSupplyRating- Voltage-105/125volts Frequency-50/60cycles/sec. Wattage -150watts OverallDimensions- 0 _7 I CJ CJ, r-4 r-4 pabinetModel- Rack Model- Ieifiht- CabinetModel - lgX lgX highX highX deep deep Rack Model - - 2 - shouldbe I (J (J I rl rl INTRODUCTORY The-hp-Model335c,335DTVAuralCarrierFre- quencyMonitorandModulationMeterhasbeendesignedfor monitoringthecarrierfrequencyandmodulationofTVAural broadcastransmitters. Theinstrumentalsodemodulatesthecarrierto provideessentiallydistortion-freeaudiooutputforaural monitoringandformeasuringtransmitterperformancechar- acteristics.Theinstrumenthasbeencarefullydesigned toprovidetheutmostinstabilityandintrouble-free performance.Thecarrierdeviationmeterreadsthecenter frequencywithoutbeingaffectedbymodulationanddoesnot requirefrequentcalibrationadjustments.Theperformance oftheequipmentistoahighdegreeindependentofmonitor- ingpowersuppliedbythetransmitter,linevoltagevariations, tubecharacteristics,andtemperaturechangeswithintherange ofvariationnormallyencounteredinbroadcastservice. Inadditiontomonitoringthecarrierfrequency andmodulationofthetransmitter,theModels 335C, 335Dallow measurementof(a)incidentalAMmodulation,(b)FMnoise, and(c)percentagemodulationofthetransmitterbythe carriernullmethod. Thismanualpertainstorackstyleandcabinetstyle instruments. OPERATINGINSTRUCTIONS UNPACKING Thecrystaloven,itscrystal,andthe150kc/s checkcrystalusedinthisinstrumentarepackedseparately tominimizethepossibilityofdamageintransit.The crystalovenshouldbeunwrappedcarefullybeingcarefulnot todamagethethermometerprotrudingfromthesideofthe oven.TheRFfittingsfortherfinputcable(notsupplied) arealsopackagedwiththecrystaloven. Thecrystalovenandcheckcrystalshouldbeplaced intheirsocketsbeforethedustcoverisreplacedinthis inspection. - 3 - 0 -:t , CJ CJ r-l -r-l Q o If l l INSTALLATIon Location Specialprecautionsshouldbetakentoinstallthe Models335C,335Dsothatagenerouscirculationofairis maintained.Inordertoobtaingoodcirculation,itisdesir- abletomounttheinstrucentabovepatchcordpanelsorother lowpowersystems.Theinstrumentcanbeoperatedinquite highambienttemperaturesifthisprecautionisfollowed. Innocaseshouldtheinstrumentbeoperatedin surroundingssuchthatthecrystaloventhermostatloses control;thecrystaoventhermostatpilotlampshouldflash intermittently,showingthatthetl1ermostatiscontrolling thoventemperature.Ifthelampdoesnotlight,theairflow aroundtheinstrumentShouldbeincreased. ElectricalConnections Therearethreesetsofelectricalconnectionstobe madetotheModel335cand/orModel335D.Alloftheseconnec- tionsaremadeonthebacksideoftheinstrument: (I)Themotorbasetypeplugontheinstrument shouldbeconnectedtoanominal115-volt,50/60cyclesingle phasesupply.Itshouldbenotedthatthepowersourcefor theovenisconnectedpermanentlyacrosstheinputcircuit aheadthepowerswitchsothatthecrystalwillbemaintained atthepropertemperaturewhentheequipmentisturnedoffand notinuse. (2)AcoaxialtypeconnectorNavytype-49194is providedandshouldbeconnectedtothemonitoringpick-uppro- videdbythetransmittermanufacturer.Fifty-ohmcoaxialcable suchasRG-8/UshouldbeusedtoconnecttheModel335cand/or Model 335Dtotepick-uploop.Relativelylonglengthsof cablecanbetoleratedforthisconnection.Directionsfor adjustingthemonitoringpick-uponthetransmitteraregiven onpageofthismanual. (3)Aneight-pointterminalstripprovidesconnec- tionsforaudiooutput,anexternalmodulationmeter,and externalpeakmodulationindicatorlights. aMonitoringOutput:Whenterminals3and4are connectedtogether,terminals1and2provideanaudiosignal forfeedinga 600-ohmbalcedcircuit.Thenominaloutputis 1.5volts(4mw)at100modulationatlowmodulatingfrequencies. (b)HighLevelOutput:Ahighleveloutputispro- videdbetweenterminal3andground(terminal5)forusewith anoiseanddistortionanalyzerorahighimpedancemonitoring amplifier.Thenominaloutputis10voltsat100%modulation - 4 - , CJ CJ I r-l r-l atlowmodulatingfrequenciesandtheappliedloadshould notbelessthan20,000ohms.Whenmakingnoiseanddistor- tionmeasurements,terminal4shouldbedisconnectedfrom terminal3topreventanyundersirableloadingbythemonitor- ingcircuits. (c)ExternalModulationMeter:Termina!s5and 6arenormallyjoinedbya1000-ohmresistor.Ifanexternal modulationmeteristobeused,thisresistorshouldbere- movedandthemeterconnectedbetweentheseterminals,6 beingthepositiveconnectionand5(ground)thenegative. Theexternalmetershouldbeidenticaltotheoneinthe instrumentinordertoindicateaccuratelyandhavetheproper dynamiccharacteristics.Itisrecommendedthatextramodu- lationmetersbeobtainedfromtheHewlett-PackardCompany, givingtheserialnumberoftheunitforhichtheyareintended. (d)ExternalPeakModulationIndicator:Anexternal indicatinglampmaybeplacedinparallelwiththeoneinthe instrumentbyconnectingitbetweenterminals7and8.Either a3-ora6-watt,120voltlampmaybeused.Not morethan afewhundredmicromicro-faradsofcapacityshouldbeintro- ducedbythisconnectionsothatitisdesirabletouse shortlengthsoflowcapacitycable. Allleadsconnectingtotheterminalstripand ACpowerconnectionsshouldbeisolatedfromstrongRFfields, preferablyusingshieldedwire. InitialAdjustments Theinitialadjustmentsforthisunitarethe sameastheusualoperatingadjustments,exceptforthead- justmentofthetransmitterpick-uploop.Thefollowing adjustmentsshouldbemade whentheModel 335Cand/orModel 335Disfirstinstalledandasoftenasdesiredthereafter: (1)Turnontheinstrumentandallowaheating periodofatleastafewhours,becausethemaincrystalwill takesometimetobeheatedtoitspropertemperature.Dis- connectthepick-uploop.Duringthewarm-up,keepaclose checkreadingonthecrystalthermometerwhichisvisible throughthefrontpanel.Ifthereadingofthisthermometer overshoots65C byanyappreciableamount,thecauseusually willbefoundtobethatthemercurycolumnineitherthe thermometerorthermostatisnotunited.Thesecolumns canbere-unitedbyremovingtheunitinquestionandalter- natelyheatingandcoolingtheunit. .Steps2and5belowcanbeperformedafteronly afaminuteswarmup,althoughaslonga warm-upaspossible shouldbeallowedbeforeperformingstep6. (2)OpenthepaneldoorandsettheCALIBRATE- USE-CARRIERLEVELswitchtotheCALIBRATEposition.The CARRIERDEVIATIONmeterwillreadclosetocenterscaleand - 5 - II thePERCENTMODULATIONmeterwillreadapproximately100%. AdjusttheSETTOZERODEV.controlsothatthe CARRIERDEVIATIOWmeterreadsexactlyzero.Adjustthe SETTO1001tcontrolsothatthePERCENTMOIDLATIONItmeter readsexactly100%.Thesecontrolsadjustthecountercircuits tonormaloperation. (3)SettheCALIBRATE-USE-CARRIERLEVEL switchtoapositionhalfwaybetweenUSE andCARRIERLEVEL. Thereisadetentmechanismatthispoint,althOUghnot labelledonthepanel. AreadingonthePERCENTMODULATIONItmeterbetween 40and75willbeobtainedwithnosignalcomingfromthe transmitter.Thisreadingshouldbepeakedbyadjustingthe condensermarkedItMULT.onthechassis(notonfrontpanel). Withthiscondenserpeaked,-areadingofatleast40on thePERCENTMOWLATIONItmetershouldbeobtained. (4)ThecondensermarkedOSConthechassis shouldnotneedadjustment.However,ifareadingofless than40isobtainedwiththepreviousadjustmentin(3)above, itmaybedesirabletoretunetheoscillatortankcircuit whiohwillbefoundtovaryslowlyononesideofthe maximumandrapidlyontheotherside.Thepropersetting forthiscondenseristhatwhichillgiveareadingabout 15%(Model335c)or30%(Model3350)belowthemaximum on thesidewhichvariesslowly.Thisadjustmentisnotcritical, sinceitaffectsonlyslightlythefrequencyandstability oftheorystaloscillator. (5)Next,etthe.CALIBRATE-USE-CARRIER LEVELswitchtotheCARRIERLEVELpositionandadjustthe pick-Uploopinthetransmittertogiveareadingbetween 50and100onthePERCENTMODULATIONmeter.Thecarrier inputlevelisnotcritical.The powerfromthetransmitter canbeadjustedfromaboutone-tenthofawattto4watts withoutaffectingtheaccuracyoftheModel 335Cand/or Model 335D. ThereadingonthePERCENTMODULATIONmeterwith theswitchintheCARRIERLEVELpositionisapproximately proportionaltotheinputvoltage.With10voltsofRF voltagefromthetransmitter,areadingofapproximately 100%willbeobtainedonthePERCENTMODULATIONmeterwith theswitchintheCARRIERLEVELposition. (6)Thefrequencyofthecomparisonoscillator intheequipmenthasbeenadjustedtothespecifiedchannel atthefactoryandcanbeexpectedtobewithina fewhundred cyclesofthecorrectfrequencywhentheinstrumentisreceived. Aftertheequipmenthasbeenturnedonforseveralhours,the temperatureofthecrystaloenwillcome upto650C.If itisdesiredtocheckthefrequencyofthemonitoragainst - 6 - astandardtransmission,thismaybedoneandthefrequency ofthemonitorcanbeadjustedbymeansofthescrewdriver adjustmentmarkedCRYSTALTUNINGunderthecoveronthe frontpanel.Thisadjustmentshouldbe madewiththeswitch intheUSEposition. (7)Theinstrumentisnowreadyforoperationand onlythoseadjustmentsdescribedunderMaintenancettinthis manualshouldberequired. o + CONTROLS CALIBRATE-USE- CARRIERLEVEL SErTO100% SETTOZERODEY. CRYSTALTUNING MODULATIONPOLARITY PEAKMOOOLATION INDICATOR CRYSTALTEMPERATURE Connectfrontpanelmeterssoasto enabletheinstrumenttobecalibrated, tochecktheperformanceofthecompar- isonfrequencymultipliercircuits,and tomeasurethecarrierinputlevelfrom thetransmitter. Adjustscurrentinfinalswitchingtubes topropermagnitudetoinsurethatsen- sitivityofboththeCARRIERDEVIATION ndicationandPERCENTMODULATIONindi- cationarecorrect. AdjustsbalancingcurrentinCARRIER DEVIATIONmetersothatzerodeviation isindicatedwhenexactly150kcis appliedtothecountercircuits.This adjustmentismadeintheCALIBRATE positionoftheUSE-CALIBRATEswlh Inthispositiona150kcvoltagefrom anintrnal150kccrystal-controlled oscillatorisappliedtothecounter circuits. Adjustsfrequencyoflocalcrystal-con- trolledcomparisonoscillatorsothe monitorcanbeadjustedtoreadzero deviationforthecorrectfrequency. Connectsthemodulationandpeakindica- torssotheyrespondinaccordancewith eitherpositiveornegativeswingsof modulation. Adjuststhefiringpointofthepeak modulationindicatorlamp sothemodula- tionlevelatwhichtheflashwillbe obtainedcanbeset. Therometerwhichindicatestemperature withincrystaloven;normaltemperature isapproximately650c. - 7 - POWERON FUSE-2A, FUSE-.25A Controlsthepowersuppliedtothe instrumentfromthepowerline.The crystalovenheateranditstemperature controlsareconnecteddirectlytothe powerlineandarenotcontrolledbythe POWERONswitch. Thesefuseholderscontaina 2ampere anda.25amperecartridgefuse.The fusemaybereplacedbyunscrewingthe fuseholdercapandinsertinga newfuse. a, -7 I CJ (J I r-l r-l Inaddtiontothesecontrolsonthefrontpanel, threecontrolsarelocatedonthechassisoftheuipment.A potentiometerR49,locatedonaterminalboardattheleftside .underneaththechassis,isprovidedtoadjustthevoltageregu- latorcircuitifnecessarywhenthevoltageregulatortubes arechanged.Ascrewdrivercontrolofthetuningcondenser (OSC)inthecrystaltankcircuitislocatedjustbehindthe crystalovenontopofthechassis.Furtherbackofthepanel inthesameareaislocatedthecrystalmultipliertankcircuit control(MULT)whichisalsoascrewdriveradjustment. Vlhentheequipmenthasbeeninstalledandadjusted inaccordancewiththeforegoinginstructions,nothinofurther isnecessaryduringtheoperationexcer.toccasionallytocheck thereadingsoftheCARRIERDEVIATIOnmeterandtheMODULATION meterintheCALIBRATEposition.Anyvariationsfromthese readingsmaybecorrectedfromtimetotimeby meansofthe SETTOZERODEV.controlandtheSETTO100control. Itmayalsobedesirableoccasionallytocheckthe carrierlevelbyreturningtheswitchtotheCARRIERLEVEL positionandreadingthemodulationmeter.Anyreadingin thispositionbetween50and100willprovidesatisfactory operation. OverModulationIndicator ThemodulationmeterintheModel335candModel 335D TVAuralCarrierFrequencyMonitorandModulationMeterh s beendesignedsothatitwillindicate90%ofthevalueofa modulationpeakof85millisecondsduration.Further,the modulationmeterwillfallto10%froma 100%readinginnot lessthan500millisecondsandnotmorethan800milliseconds afterthecompleteremovalof100%modUlation.Thesedesign requirementsareinaccordancewithFCCstandards. Inpractice,however,manyburstsofmodulationin atypicalprogramareofmuchshorterdurationthan85milli- seconds-perhapsoneortwomilliseconds-andtheModels335C, 335D donotindicatethefullpeakvalueofmodulationbursts ofextremelyshortduration.Nevertheless,theseshortintervals ofhighmodulationareimportant,because,ifsubstantial - 8 - .3- I N (J I overmodulationoccursonsuchpeaks,theresultmaybedetected inreceiversandalsomaycauseadjacentchannelinterference. topreventtheseconditions,itisrecommended CDbe0eratedwiththeirovermodulation austnno ssenotherthan(and taemouaton0etransmttere aJustesohatocca- sionalflashingoftheovermodulationindicatinglampisobtained withcommonprogrammaterial.Thiswillmeanthatthegeneral programlevelwillresultintheorderof50modulationas indicatedbythemeter.ModulationpeaksofshortdurationwIll behigherthanthisvaluebutprobablywillnotexceed100%. Thisconditionofoperationisdesirableasitpermitsthetrue capabiliiesofhighquality,uniqueonlytoFMmorenearlyto berealized.Overmodulationistobeavoidedasitresultsin considerabledeterIorationoftheprogramquality. Anylimitingampliierusedintheaudiosystem shouldbeessentiallyinstantaneousinitsaction.Limiting amplifiershavingacontrolactionslowerthanafewmilliseconds willpermitmodulationpeaksgoingconsiderablyabovethe100% level.Thisemphasisofshortmodulationpeaksbylimiting amplifiersisparticularlybadinFMSystemsduetothepre- emphasisofthehighfrequenciesinthesystem.Thereforeit1s recommendedthatlimitingamplifiersbeavoidedunlesstheir characteristicsandeffectsontheentiresystemarewellknoWQ. MEASUREMENTS 1ffiASUREMEIITOFINCIDENTALAMPLITUDEMODULATIONONFMBROADCAST CARqIERS A.specialjackisprovIdedinthe-hp-Model3350and 335DtofacilitatethemeasurementofspuriousAMmodulation onthecarrierofFMbroadcasttransmitters.Thisjackislocat- edonthebackoftheinstrumentandismarkedJ3.Measurements ofspuriousAMmodulationcanbemadewiththeuseofthis jackandasensitivevacuum-tubevoltmeterinthefolloWing manner: (I)CoupletheunmodulatedRFvoltagefr