HP-450A-Manual-SN-010 电路图.pdf

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1、HP Archive This vintage Hewlett Packard document was preserved and distributed by Pleasevisituson the web! Scanned by on-line curator: Tony Gerbic * For FREE Distribution Only * RadioFans.CN 收音机爱 好者资料库 450A AMPLIFIER SERIALSPREFIXED:010- ! , I ! I PRINTED1/61I 00001-1 i RadioFans.CN 收音机爱 好者资料库 ) ) 0

2、00011 OPERATINGANDSERVICINGMANUAL MODEL450A SERIALSPREFIXED:010 - AMPLIFIER CopyrightHEWLETT-PACKARDCOMPANY1961 ISOIPAGEMILLROAD.PALOALTO.CALifORNIA.U.S.A. Printed:JAN1961 RadioFans.CN 收音机爱 好者资料库 Model 450A TAILEOF CONTENTS TableofContents ListofIllustrations ) SectionPageSectionPage GENERAL INFORMA

3、TION1-1IVSERVICE INSTRUCTIONS. .4-1 1-1.Description. . . .1-14-1.Warnings andCautions.4-1 1-5.ApplicableLiterature1-14-4.EquipmentRequiredforMaintenance4-1 4-6.Troubleshooting. . 4-2 4-8.TubeReplacement. . . .4-2 IIOPERATING INSTRUCTIONS.2-14-10.LocatingShortsinPowerCircuits4-2 2-1.Incoming Inspecti

4、on2-14-12.TestingPowerSupplyOperation.4-2 2-4.Installation.2-14-15.MeasuringAmplifierStageGain.4-3 2-10.OperatingProcedure2-24-17.AmplifierAdjustments. . . .4-3 4-19.Adjusting VI andV2HeaterVoltage4-3 4-21.AdjustingAmplifierGain. . 4-3 IIITHEORY OF OPERATION.3-14-23.NoiseandDistortionMeasurement4-4

5、3-1.AmplifierCircuitOperation. .3-1VREPLACEABLE PARTS .5-1 3-4.RegulatedPowerSupplyOperation3-15-1.Introduction.5-1 3-6.DCHeaterSupply. . . .3-15-3.OrderingInformation5-1 LIST OFILLUSTRATIONS )NumberPageNumberPage 1-1.Tableof Specifications .1-04-3. Top View of Model 450A . .4-6 1-2.Model 450AAmplif

6、ier1-0 4-4.Bottom View of Model 450A4-7 4-1.TestSetupforMeasuringAmplifier 4-5.Voltages andResistancesonTube Gain.4-3 Sockets andTerminalBoards4-8 4-2.TestSetupforMeasuringAmplifier DistortionandNoise. . . . . .4-44-6.SchematicDiagramModel 450A . .4-9 ) 00001-1 iii Section I Figures1-1 and1-2 GAIN:

7、FREQUENCY RESPONSE: STABILITY: IMPEDANCE: OUTPUT LEVEL: DISTORTION: Model 450A 40 1/8db (100X), 20 1/8db(lOX)at1000cps. For40 db gain (opencircuit):5cpsto2megacycles,within 1 db; 10cpsto1megacycle,within 1/2db. For20 db gain (opencircuit):2cpsto1.2megacycles,within 1 db; 5cpsto1megacycle,within 1/2d

8、b. 2% withlinevoltagechanges(115/230voltsHYfo)andnormal changesin tubecharacteristics. Input: 1megohmshuntedbyapproximately15 pf. Output: 150ohmsmaximumoverfullfrequencyrange. 10voltsmaximuminto3000ohmsorhigherresistiveload. Lessthan1%distortionfrom2cpsto 100kcatratedoutputandload resistance;lesstha

9、n2%above100 kc. NOISE:For40 db gain: For20 db gain: Equivalentto40microvoltsatinputterminals. Equivalentto250microvoltsatinputterminals. POWER: DIMENSIONS: WEIGHT: ACCESSORIES AVAILABLE: 115/230volts HYfo,50to1000cpsac,50watts. CabinetMount:8-5/8in. wide,5-1/2in. high,10-3/4in.deep. RackMount:19 in.

10、 wide,5-7/32in. high,10-9/16in.deep. CabinetMount:Net 10lbs;shipping14lbs. RackMount:Net11lbs;shipping24lbs. AC-16ACableAssembly(terminatesin dual banana plugs 44in.long). AC-16BCableAssembly(dual banana plugtoBNCmale45 in. long). Figure1-1.TableofSpecifications AMPLIFIER MODELctj)450A HEWLETTPACKAR

11、D ,AUlAl.TOCAUFOflHIA INPUT 40DB ;( GAIN 20DB POWER ON OUTPUT 1-0 Figure1-2.Model 450AAmplifier 00001-1 Model 450A SECTION I GENERALINFORMATION SectionsI andII Paragraphs1-1to2-7 1-1.DESCRIPTION. 1-2.TheModel 450Aisageneral-purpose,stabi- lized,fixed-gainamplifierforusewithlow-level signalsfrom2cpst

12、o2mc.Itprovidestwocalibrated gainfactors,lOX(20 db) and 100X (40 db),selectable by a toggle switch onthefrontpanel.Eachgainfactor isaccuratetowithin1/8db in the audiofrequency range;frequencyresponseisgiven inthetableof specifications(figure1-1).Principalcharacteristics: stablegain withsmoothattenua

13、tionbeyondratedfre- quencyrange,widefrequencyrange,lowdistortion. 1-3.Typicalusesincludeincreasingthesensitivity ofactestequipment(voltmeters,oscilloscopes, bridges,etc), obtaininglargersignalsacrosslower impedancesintestbenchsetupsandpermanentsystem installations.Anelectronically-regulatedpower sup

14、plyandlargeamountsofdegenerativefeedback aroundtheentireamplifiercircuitprovideveryre- liableandstableoperationincaseof changingline voltage,loadresistance,ortubecharacteristics. 1-4.Theamplifierisconstructedon asinglechassis withremovablecoverand bottomplate.Aleather carryinghandleisprovidedonthele

15、ftsideofthe cabinetmodel.Thefrontpanelisfinished inlight greyenamel;therestofthecabinetisfinished in darkgreywrinklepaint.Operatingcontrolsandter- minalsconsistoftoggle-typepowerand gainswitches and bindingposttypeinput and outputterminalson thefrontpanel.Bindingpostsarespaced3/4inch on-centerstorec

16、eivedualbanana-plugconnectors. Thepowercableispermanentlyattachedtotherear oftheamplifierandisterminatedin a3-prong, grounding-typeplug.Afuseisprovidedontherear andcanbereplacedexternally. 1-5.APPLICABLELITERATURE. 1-6.Thishandbookcontainscompleteoperatingand servicinginstructionsforthe450AAmplifier

17、and conformstotheformatspecifiedin MIL-M-5474C. ) SECTIONII OPERATINGINSTRUCTIONS ) 2-1.INCOMINGINSPECTION. 2-2.MECHANICAL.When unpackingtheamplifier, inspectitforanysignofphysicaldamage.Ifthe cabinetisdamaged,removecoverand bottomplate andinspectchassispartsforfurtherdamage.Re- portalldamagetotheca

18、rrierand keepamplifier intactforinspectionbycarrierandinsurer.Allin- strumentsshippedbytheHewlett-PackardCompany areinsuredagainstshippingdamage.SeeWarranty atrearofmanual. 2-3.ELECTRICAL.Electricalinspectionconsists oftestingcertainelectricalcharacteristicsofthe amplifiertodeterminethatitfunctionsn

19、ormallyafter having beenstoredortransported.Onlyonetestis required;fullinstructionsaregiven inparagraph 4-20stepsa throughf. 2-4.INSTALLATION. 2-5.INPUT CONNECTIONS.Theamplifiercanbe connectedtoasignalsourcethrougheithertwisted pairleadsorshieldedcable.Keep inputleadsas shortaspossibletoavoidexcessi

20、vecapacitiveshunt- ing ofthesignalsource.Ifnecessary,usecoaxial cabletopreventunwantedsignalpickupfromstray electricand magnetiCfields.00NOTconnectthe amplifierinputtocircuitpotentialsgreaterthan 00001-1 400voltsunlessanexternall-j.lfcapacitorhavingsuf- ficientvoltageratingisusedinserieswith the inp

21、ut terminals. 2-6.OUTPUT CONNECTIONS.Theamplifieroutput canbeconnectedthrough any convenientleadsetor cable.Thelow outputimpedanceof150ohmspermits shieldedcabletobeusedfreelywithoutcapacitive loadinginthe audiorangeandpermitstwistedpair leadsto beusedwith muchlesseffectfromstray fields.Theamplifieri

22、sdesignedtobeusedwith resistiveloadsof 3000ohmsormore.Loadsbelow 3000ohmsreduceamplifiergain bandwidth, andmaxi- mumoutput voltageavailable.Forhigherfrequencies, theloadmusthavesmallcapacitivereactancetopre- servefull outputsignalqualityandstability.DONOT connecttheoutputterminalstodcpotentialofmore

23、 than+50or-300volts,oroutputcapacitorratings will beexceeded. 2-7.CONSIDERATION FOR LOW SIGNAL LEVELS. When amplifyinglow-levelsignalsitmaybenecessary toeliminateanelectricalgroundloopformedbythe powercablegroundleadandsignalgroundleadbetween twoinstruments.Ifthiselectricalpathiscompleted (typically

24、 acombinationofthesignalground andpower linegroundleadsdo),linefrequencycurrentsflow in thesignalgroundleadand developvoltagesacrossthe leadswhichareinserieswiththedesiredsignal.To 1-1 2-1 Section II Paragraphs2-8to2-11 avoidthissituation,selectoneground pathfroma groupofinstrumentsconnectedtogether

25、,andpermit noothergroundpathtothepowerlineground. Groundingoneoftheinstrumentsmaygivelessripple troublethan grounding anyother;orungroundingall instrumentsmaygivelowestline-frequencymodu- lationofthedesiredsignal. 2-8.POWER CABLE.Theplug onthepowercable hasaroundgroundingterminalcombined withstand-

26、ard,2-prongplug.Iftheacoutletwill notaccommodate thisplug, anadaptermustbeused.Theround pin on thispluggroundstheamplifierchassis.Whenthe adapterisused,thechassisconnectionisapigtail leadextendingfromtheadapter,which shouldbecon- nectedtoa groundedacoutletmounting boxtoground thechassis. 2-9.POWERLI

27、NEVOLTAGE.Theamplifieris shippedfromthefactoryforoperationon 11S-volt 2-2 Model4S0A acpower,unlessotherwisespecified.Thepower transformercanbereconnectedforuseon230-volt powerbyconnectingitsdualprimarywindingsin seriesasshown ontheschematicdiagram,note1. Aftersuchconversion,replacethe0.8-amperefuse

28、withan0.4-ampereslow-blowfuse. 2-10.OPERATINGPROCEDURE. 2-11.Theonlyoperatingprecautiontobekeptin mindaretheinstructionsinparagraphs2-Sand2-6 regardingexcessivedcvoltages.Foroperationin undesirableatmosphericconditions,provideany physicalprotectionpossibletopreventmechanical damage,andoperateamplifi

29、erasusual.Donot obstructventilatinglouvers.Thepowercordmaybe leftconnectedtothepowersourceduringperiodsof non-operation. 00001-1 Model 450A SECTIONIII THEORYOFOPERATION SectionsIIIandIV Paragraphs3-1to4-5 ) 3-1.AMPLIFIERCIRCUITOPERATION. 3-2.Theamplifiercircuitconsistsof twostagesof high-gainvoltage

30、amplificationand acathodefollower outputstageconnectedasshown intheschematic diagram.Pentodetubesareusedinallthreestages forwide bandwidth with lownoise.Thetriodecon- nectedcathodefollowerpresentsarelativelylow sourceimpedanceattheOUTPUTterminals.De- generativefeedbackiscarriedaroundtheentire amplif

31、iertostabilizegain.Theamount ofdegen- erativefeedbackisadjustedby theGAINswitchto obtain 20or40 dbamplification.Theresistivefeed- backcircuitisshuntedby asmalladjustablecapacitor forgaincompensationathighfrequencies.Resistance- capacitancecouplingisusedbetweeneachstage. Cathodebiasisusedateachstage.

32、 3-3.Degenerativefeedbackistakenfromtheampli- fieroutput through aresistivedividerconsistingof R3and R6tothecathodeofthefirststageVI.The R3AportionofthedividerisshortedbytheGAIN switchSltodecreasefeedback andincreasegainto 40 db.ResistorR6providesfineadjustmentof gain forcalibrationpurposes.Capacito

33、rsCllandCl2 providegaincompensationathighfrequencies. 3-4.REGULATED POWER SUPPLY OPERATION. 3-5.Thepowersupplyfortheamplifieriselectron- icallyregulatedtostabilizeoperationduringchanges inlinevoltageand tominimizelinefrequencymodu- lationoftheoutputsignal.Theregulatedsupply consistsofpowertransforme

34、rTI.rectifierV4. seriesregulatortube V5,regulatoramplifierV6and vOltagereferenceV7.Theseriesregulatorisa cathodefollowerwhosecathodesuppliestheregulated voltagetotheloadconsistingofVI,V2and V3.The seriesregulatorservesasanadjustableimpedance controlledbyamplifiedfeedbackfromV6.Ampli- fierV6samplesth

35、eregulatedvoltage andamplifies anydifferencebetweenitandthereferencevoltage providedby V7. Voltagecomparisonisaccomplished by applying thesamplevoltagetoV6gridandthe referenevoltagetoV6cathode.If theregulated voltagetendstorise,V6amplifiesthisincreaseand appliesittothegridofV5causingtheimpedanceof V

36、5toincrease,thusinstantlyandexactlycounter- actingtheoriginaltendencytoincrease.Thisgrid controlautomaticallyholdstheseriesregulator cathodevoltageconstant.Thehighplateresistance oftheseriesregulatortubeassistedbyamplifier feedbackattenuatesrippleandstabilizestheoutput voltageduringchangesinlinevolt

37、age andrectifier output.ThehightransconductanceofV5.assisted bythesamefeedback,stabilizesthecathodevoltage duringchangesin loadcurrent.Thesampleof the regulatedoutputisobtainedfromresistivedivider R24 and R26.ResistorR25isselectedtoadjustthe valueoftheregulatedvoltageto+210volts. 3-6.DCHEATERSUPPLY.

38、 3-7.DCvOltageissuppliestotheheatersofVI,V2 andV3topreventline-frequencymodulation ofthe outputsignalthroughheater-cathodeleakageinthe tubes.Thisvoltageisobtainedfroma9-voltwinding onthetransformerrectifiedby afull-wavebridge rectifierCRI.TherectifiedvoltageisfilteredbyC7. ResistorR27providesadjustm

39、entoftheheatervoltage toaccommodateagingchangesinrectifierresistance. SECTIONIV SERVICEINSTRUCTIONS ) 4-1.WARNINGSANDCAUTIONS. 4-2.Theamplifiercontainsaseleniumrectifier. Whenseleniumrectifiersburnout due tooverheating, poisonousfumesarereleased.Ventilateimmediately, and do notinhalethesefumes.Donot

40、 handlethe rectifieruntilithascooled. 4-3.Do notremoveVIorV2withtheamplifier turnedon.Thesetubesaresuppliedwithunregulated dcheatervoltage.IfVIorV2isremovedwiththe amplifieroperating,theheatervoltage on there- mainingtube willrisesharplyandpossiblydamageit. 00001-1 4-4.EQUIPMENTREQUIREDFOR MAINTENAN

41、CE. 4-5.Generaltroubleshootingrequiresanelectronic multimetersuchastheHewlett-PackardModel 410B. Othermultimeterscanbeusediftheyhave20,000 ohm/voltsensitivityorgreater.Tocalibratethegain oftheamplifierrequiresanacsignalsourceandan accurateacvoltmeteroftherequiredfrequencyrange, suchastheHewlett-Pack

42、ardModel 650AOscillator and4000Voltmeter.Othertestinstrumentscanbe usediftheyprovidethenecessaryfrequencyrange andaccuracy.Tomeasuredistortionfromtheampli- fierrequiresasignalsourceproducingasignalwith 3-1 4-1 SectionIV Paragraphs4-6to4-14 Model 450A 4-12.TESTING POWER SUPPLY OPERATION. 4-13.Theampl

43、ifieremploysanelectronically-regu- latedpowersupply withverylowline-frequencyripple. Totestoperationofthesupply,proceedasfollows: circuit,powertransformerwindings,orin thetrans- formerprimarycircuit.Theresistanceofeachtrans- formerwindingisasfollows: 8ohms 8ohms RESISTANCECOLOR Black-Black/yellow Bl

44、ack/red-Black/green Brown-Brown0.14 ohm Yellow-Yellow0.06 ohm Green-White0.18 ohm Green-Red0.12 ohm Red-Yellow105ohms Yellow-Red105ohms *Fil.#4partof windingforFil.#3. WINDING Pri.#1 Pri.#Z Fil.#l(6.3v) Fil.#2(5 v) Fil.#3(9v) *Fil.#4(6.3 v) H.V.#1 H.V.#2 lessthan 0.5%distortionand adistortionmetersu

45、ch astheHewlett-PackardModel 202COscillatorand 330BDistortionAnalyzer.Thefrequencyrangeof the330Bisconsideredadequateforthisapplication. Measurementofdistortionathigherandlowerfre- quenciesrequiresrejectionfiltersnotreadilyavail- able.Avariablelinetransformerisrequiredto producelinevoltagesfrom100to

46、130volts. 4-6.TROUBLESHOOTING. 4-7.Thefirststepinservicingadefectiveamplifier istoinspectforanysignofoverheating,physical damage,orwear.Thesecondstepistoattemptoper- ationtoseeifthefuseblows,pilotlamplights,and iftheamplifiercanbeoperatedwithoutdamage. Therearetwosetsofoperationaltests:powersupply c

47、hecks(seeparagraphs4-10,4-12and4-18)and amplifierchecks(seeparagraphs4-15,4-20and 4-22).Suspectelectrontubefailurefirst,thenas- sociatedcircuitry.Lookforintermittentandmargi- nalmalfunctions.Thesetypesoffailurescansome- timesbefound whiletroubleshooting,byphysical shockand by applying low and highli

48、nevoltages whilemakingthetests. 4-1.TUBEREPLACEMENT. 4-9.Thebestwaytotesta tubeistoreplaceitwith a new one, noting anychangeinamplifierperform- ancewhilemeasuringnoiseanddistortionintheamp- lifieroutput.Ifthereplacementtubedoesnotim- proveperformance,returnoriginaltubetosocketto avoidcomplicatingthe

49、troubleshootingprocedure. Makethetestatlow and highlinevoltagetoseeif malfunctionismarginal.Ifa tubetesterisusedto checktubes,consideritsindicationsemi-finalifit showsgood,finalifitshowsbad.Tubetesters donotmeasuresecondordereffectssuchasexces- sivechangeintransconductance,platecurrentand gridcurrentwithchangesinheatervoltage,noise, microphonics,heater-cathodeleakage,etc,which maybeimportantincertaincircuits.Remember thatmosttubefailuresoccurduringthefirsthundred hoursofoperation.Afterthisperiodtubesageslowly andshouldnot be