HP-3450A-Mods-TS 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 J I : . .-)- 34501 1ultiful1ctieJllJ),I1 TROUI3LESIIOOTLGGCIDE TableofContents Secion Introduction

2、. SilnplifiedBlockDiagraln TroubleshootingTree. Troubleshooti.sInforrl1ation. TIleQuickFi. . . . . . :vIasterTilnin;BlockDiag-ran1 . . RangeBlockDiagran1. CurrentSer-iceLiterature. 1 2 3 4-2 . 2;)-2) 30 . . 3J -4C RadioFans.CN 收音机爱 好者资料库 , J , .- . , .f .! I I I -Y T, t .-; O. ., fonl UAtILC)tlrJl C

3、) A7 SAMPLE PfRIOD I. Rotw A 7L. TIMING RES(1,;A6, R,STERTIMING91NAIlIES f-cDL_A-._ t ,/.1, .n;: -t,tc., .0 H,j. 4 ., 1 .6,.:., .!_! . -1L_R_E_A_D_OU_Tr-,. FlEDBLOCKDIAGRAM3450ASIMPLI -_ ./ 1;-1 H1- Gf-.-1 .A:;,AII, -:.,F_EX t.BLE F E / (. tHl.0 , l (Ii,/ ABc D GOOD BAD L- TroubleshootingTree 3 Trou

4、bleshooting. , A.ChpckPowerSupplies.The3450Apowersupplysystel11isdiidedintotwo sections:1)theinguardsupplieswhichusetheing-uardgroundasa IeferelHC; and2)theoutguardsupplieswhichusethechassisasareference.Thereis nothingreallyuniqueaboutthepowersupplycircuitsthatwouldrequireanyspc(jll troubleshootinte

5、chniques.Troubleshootingislargelyanlateroffindingtheright circuitboardandknowingwherelhevarioussupplieslr(uspc.l.Table1giv11oIl th(nextpagewillproid(tiltbasiclayoutofthepowcrsuppl,systpnllSv(llas inforn13tioncnncerningtillocationaneluSPofeachsupply.Tilc()p(rahllgll1cl Crice1anualproid(s th( adjustl1

6、H.nt proc(clur(10r the outguarei; 4. 4()It .11ppl)andthe:17 oltinguaIdsupply. B.Ren10veAllOptionBoards.The3450Aisbasicallya 10 otDM:theohrns andACsectionsareusedtoconverttheirinputsignalsto DC l(,(s.Theother optionscontrolorprocessthedigitized111,asuren1ent.Sincetheseoptionboards canberemoedconvenie

7、ntly,aproblenlcanbeisolatedtoanyoftheoptionsor themainfran1e. RemovecircuitboardsA3,A24, A25,theOhn1sCoverter,andtheACConverter. Providea 10oItDCsignaltothe34,50A.Iftheinstru111cntwillnowfunction, re-installeachoptiononeatati111e.Aftereachoptionhasbeeninstnlled,nleasure the10 VDCsig-nalagain.Thispro

8、ceurcwilllocatetheoptionthatismalfunctioning. Troubles.hootinginfollnationfortheACConverteriscontainedintheIl078AOperating- andService1anual.Ohn1sconvertertroubleshooting-inlornlationiscontainedin ,thisguide. IftheinstrunlentdoesnotoperatewithnIloptionsre111o,(d.continuetotheJ1(xt paragraph. C,Thel1

9、asterTimingLoop.Thesecircuitsprovidea11ofthetilninsig-naIsls ellastheactualdatacountsandrendout.AInalfunctioninthissectionilllikely beapparentfron1thefrontpanel.Thesan1pleratelightandrateconlrol potentiometervillnotbefunctioningproperly.Eitherthesampleratelightwillbe flashingatsorneoddfrequencyorthe

10、light111aynotflashatall.Also,therate controlpotentiolneterInaynothaveanysampIeratecontrol. TheSa111plePeriodflip-flopoutputisavailableatA7TPI.Trigg-eranoscillos(opCat A6TP6onthepositiveslopeandobservethesarnpIeperiodvaeforn1.Thisdisplayisson1et difficulttoobtain.IfthesampleratecontrolpotentionHterwi

11、llld.iustthesanlpl(. ratethendecreasethesan1plerate.(SeeFiure1)Iftheratepotentioll1ctlrhasno eff(,(t seeFigure2.Ifthesanlplerateisbeingeneratedbuttheratelightisnot blinking,thefaultnlaybeonAll,A12ortheratelight.Ifthesanlpleperiodisnot presentatA7TPIcontinuetoparagraphL. 4 - BLOCKDIAGRAMOFPOWER SUPPL

12、Y SYSTEM .,:.1 f,: _.J.,iI.-,.,()1 If!)fJpI!. A,Afi A,)3,46,A57,A59,A60,A72 -.- A59(OHMSRtfERfCr) Ar.4!,?:.!25_ +17V!20m 6.5!IVA/4 t2!V +SO.SVAS,:J,:60,Ab I-+-.-.- - 1-_-+-_-_5.-t-:.:.-:-5_.!:.6. I 1-_.;-i_t.5_._A_:.!-._._._ 453,A5 1-+-+- -9;!.A5 -+-_._- -.- -_._.- .-_.- - - 414 I- AS4A)S,A,)6,A57 L

13、-J-i-t- S E C a N D A R I E S -1 I A59 DIODES T2-_. S AI5 DIODES E C a N 0 A R I E S TI POWER TRANSFORMER PRIMARY _J I,UAC _,.r,r.AA47,!l.8,A .4V 7., , TABLE1. 5 I -380ms- I :.-/00ms-i Fil1r(1.SllnpIePeriodwithnorate(ontr()l. -380ms-1 t7 lOOms-.j Figure2.SanlplePeriodvithratecontrol. D.Detern1inethe

14、Typeof Malfunctio.n.Trytodeternlinet1(g-eneralaraofthe trouble.Refertothetreeforth0varioustroubleshootinsections.Asan ex,lInpIc,ifthefrontpanelisindicating-overload,proceedtoparagTlphE. E.Overload.Ifthefrontpanelindicatesovcrlold,shortA6TP2toA6TP3.This willf!:enerateafalsezero-detect.Iftheproblenlis

15、associatedwiththeanalog- portionoftheinstrument,thefrontpanelreadoutwillbeapproxinl:1tely45000tu 50000counts.Ifnot,proceedtoparagraphLorparagraphF. ThepurposeoftheanalogsectionoftheinstrU111cntistog-eneratet110zero-detect signalandtransmitthatsignalthroughthepulsetransforn1ertothetirnigecion. Ifthis

16、signalisnotreceived,theDataCounterswillcontinuetocountun.il-erloadis reached.Ifshortingthesetwotestpoints,A6TP2andA6TP3.doesprc.n-idea zero-detectsignal,theneitherazero-detcctisnotbeingreneratedoriisnot beingtransnlittedfron1theanalogsection.Shortingthesehvot0stpointspro-idpsa falsezero:detecttothet

17、iminsection.Thissignalisat7 5 andi.g(neri.t.(dbyA6ICG. .AMPLIFIERCHECK The3450Aanalogall1plifiersInustbezeroed.Checkthean1pIHierZ0f(JSusinthe 3450AOperatingandServiceManualpae5-8.Ifthesezerosareallokaycheck theanlplifiervaveforms.SeeFigures3and4.Thefibruresshowthevarious vaveformsforbothapositiveand

18、negativeinput.If3nyanlplifi(rwillnotzero, isolatethatamplifierandprovideazeroinput.Forexan1plc,itthePoarity Alnplifierwillnotzero,renl0eA55andtheorangeleadtoth(Percent.-Il1plifier. ShorttheinputofthePolarityAnlplifiertoinguardground.IfthePolariyAnlplificr outputvillsvingfrom+to-,thenchecktheInputAmp

19、lifierandp(0nt Anplifier.If 6 I-.-. t 3 t4t7 III II Z.D. I II I -17.7V 1 totI f.-looms I I I I .-_.-_.-_.- T A57TPI INTEGRATOROUTPUT +IOV A55TPI INPUTAMP I -17.7V r -IOV 1 +17.7V I I I I I I-. I _.r.0- I I I I I 1- I I I I I I I I I I I .- 7 I -+-1-_._-. . I I I I I I I I L-,-.J-l-L Figure3.Amplifie

20、rWaveformswithpositive10voltinput. A56 POLOUTPUT I . r-.IOOms-1 1 A57TPII INTEGRATOROUTPUT - 7 ! i 17.7Y . I I I I !t . A55TPI I I INPUTAMP I -lOY I I I I, I I - )-r- I II +IOY A56 I I POLARITYOUTPUT I I II I -IOV II I II t- _. .- II I II - +-4 II I II II + .7Y I II I I A56 1 0/0OUTPUTrII I ! t I I

21、I I - 17.7Y I I I -. I I._1_. _. Figure4.AmplifierWaveformswithnegative10voltinput. 8 ) PolarityAlnplifierwillnotzero,itisunbalanciquestiontobell1sw(ncI nowis,AietheFETsokay?Ifso.thercpairwillprocc:,dfastlncteasy. Truuhl(sh()otinforeachAlllplificris(ontailHd in th fulluwing-parag-raphs. Input/nlplif

22、icr - Theinputalllplifierusesanauto-zerocircuitto ()J)lp(,IlSatpforsrn111anlouillsof an1plificroffet.Thiscircuitisoperatedbythl(l,(drelays.K7.KHiJldK!).If Kgrelayisnotworking,theinstrun1ent111ihtreadoClload.Tochcc:kthisl(ay, elect_ AIEXTa11dshortA55TP1totheKgsideofAuto-Zerocapacitor,A70Cl. Triggerth

23、einstrumentandifthefrontpanelindicationisno long-PIoverload,lhe problemisthatK9isnotclosing.Ifth(instrunlcntdoesnot COlnpoutof0erloacl, therelayisprobablyokayandtheproblen1isinthearnplifier. Thenextstepistobreakthefeedbackloopandoperatethean1plifi(r ThisisdonebyremovinRcircuitboardA2.ReI1H)Vetheshor

24、truInA70C1 toAS5TP1 andconnectashortfrol11thetopA70C1toinguardgroundandron1thetop()fAGGCl toinguardround.Connctan-hp-Model419AtoA55TP1anding-uarc1ground. AdjustingA55R14,InputAnlplifierZeroadjust,thean1plifiershouldswingfl()n1 positivetoneativesaturation. Ifthisisnotthecase,checktheen1ittcr-basevolt

25、agesoftransistorsA55Ql,Q2, Q3,Q4andQ5:-When111akingthesevoltagchecksleavetheA2Assen1blyout. 1thesetransistorsalllookgood,theproblen1n1aybethattheinputFETISare bad. ChecksforA55Q2 - Q8 Abasicin-circuitcheckforanytransistorconsistsofanseringthreequestions aboutthetransistor:1)IsthetransistorshortedB-E

26、?,2)Isthetransistor openB-E?and3)Doesthetransistorvorklikeatransistor?(i.e.doeslhe base-en1ittervoltagecontrolthecollectorvoltage.)111(3450Ashouldbein1/EXT. 1)I3ase-EI11itterShort Connectan-hp-Model412Aacrossth(base-c111ittcl,iuncti-)n.Ifthisv()ltag. forwardbiased.iszero,thentransistorcouldl(gitinll

27、tclybeturn(dntT.Jft1H- c111itterbasevoltageiszero,trytoforwardbiasthe.Inittcr-bas0junction.AsIn (xanlple,iftheen1itter-basejunctionof A55Q2 ll1CaSUl(,szero,shorttheClnitter tobaseofA55Q1A.ThisvillturnoffA55QIAtherl)byraisingQIAscollector oltage.IfthereisstillnochangeinA55Q2en1itter-baseoltagethenthe

28、transistor isshorted. 2)Base-En1itterOpen Connectan-hp-Model412Aacrosstheemitter-basejunction.Iftheforward 9 biasedYoltageexceedsavaluegreaterthan0.5to1.0volts,thcelllitttr-base junctionisopen.Again,thetransistornlaybelgitilllatelyturnedoff(i. enlitte-basevoltageiszero).Therefore.thebasevoltaeshould

29、l)( va1i(d,nd fcon1paredagainwiththeelnittervoltage.If,however,thereeverexistsan Clnitter-baseforwardbiasedvoltageofgreaterthan1volt,thetransistorisfaulty. r ) T1C1C2rcothertransi.stolfailurespossible.Acoupleofthescare: 1)OpenfrolHcollectortoelllitteland2)Shortfro!ncolI(torto(Jllilt(,l. I Fnctineihe

30、rof th0, efailuresisquitesilnilr.IftlH(olIcctot volagis i.:;cni1hC tooase-(IllitlervoltageandrenlainseJll1ewhereclosttotIHOV(,l :-=lJPPy-.henthefaultisaeollector-enlittcropen.H,inthesal11e(ase.the colecturoltageisconsiderablybelowthepowersupply,thenthefaultisa collector-en1ittershort. Ifall0:thesetr

31、ansistorscheck-outthentheproblenlis1110stlikelytheinputFETs. ThereareacoupleofwaystochecktheFETs,butprobablythefastestwayisto ren10ethesecondstage.InthecaseoftheInputAnlplifier,renl0VC A55QIA13. Connectan-hp-Model419Aacrossthedrainsof A71QIA/B.Thatis,connect the419AvherethebasesofA55QIA/Bwereconnect

32、ed.UsingA55R14 shouldbemadetoreadzeroandholdzeroplusornlinusa fewhundredInicrovolts.Ifthis isnothecase,theFETsarebad.ThisvilllneanthatA71,thepeltierchanlbcr willha-etobereplaced.Thecoolerdrivecircuitshould.becheckedtoseethatit isoperatingproperly.SeeparagraphM. ThePolarity,Ratio-Percent,andIntegrato

33、rAn1plifiersshouldbecheckedout usinthesaIneprocedureaswasusedwiththeInputAlnplifier.Ofcourse,only theInputAn1plifierusesanAuto-Zerocircuit.Therefore,starttroubleshootingthese an1pliiiersbyopeningtheirfeedbackloops.InthecaseofthePolarityArnplificrby shortingthejunctionofAI00R4andA69R8totheinguardgrou

34、nd.FortheRaUo-Percent An1plifiershortthejunctionofA56R20andA56R37toing-uardground.Forthe Integrator,shortA57Q5Agatetoinguardground,andtapeoffA57pin 5.Besureto leaethe3450AonMAN/EXT. Ifthesean1plifiersaregood,thezeroadjustpotentiorneterwillsvinthernplifi(lr ronlpositivetonegativesaturation.Refertothe

35、discussionoftheInput All1plifi(r forthE-renlainderoftrouble$hootingthesean1plifi(rs. CheckforZeroDetect/PolarityDetectSignI Ifalltheamplifierscheckoutokay,supplythe3450A vith anegative10vultsDC. ConnectonechannelofanoscilloscopetoA7TPl,thesampleperiodflip-flop. Connecttheotherchanneltotheyellowleado

36、ntheupperrightsideofthepule transfornler.ThisisthebaseofA66Ql.Thepulsetransfornlersarelocatedjust behindandtotherightoftheNixietube.TriggerthescopeatA6TP6.Thewac- forn1shoninFigure5villbeobservedonlyifthesanlpleperiodrep-ratecan1) sloweddovn.Thisvouldbedoneviththefrontpanel.sampIeratep()tentiornctr.

37、 10 ThewaveformsshowninFigure6willbeobservedifthesampleperiodrep-rate isnotadjustable.ThetopwaveisthesampleperiodandtheloverwaV(istllf polarity-detect/zero-detectsignal.Thenegativestepisthencgativepolarity-detCctand Vthepositivestepisthezero-detect.Thiswavefornlwillonlybeseenwitha negativeinput.This

38、isbecausethepolarity-detectsignal(neatiestep)only occursforanegativeinput.Forapositiveinputa2Isecpulscvilloccuratthe sametilneasthepositivestep.Sincethiszero-detcctisfastandoccursata slovrcp-rateitwouldbc1110redifficulttoscc.IJthesevavefornlsareprescnt. thentheproblellliseitherthepulsetransforrncror

39、perhapslhezero-c1etcct flip-flop.A6IC20.Ifthesinalisnotpresent,checklIHcircuitb(lw(nlhe. intcratoroutputanelthepulsetranSfOrIllcr.This(JTlsistsJllOStly(Jfthrc(Ie analoarnplificls. -1.5V r- +3.5V -_l_ L,ooms-1 380ms I . I I tot3t7 J II I lJ II II II. II Z.D. 51 II I- NEG.POLARITY DETECT Figure5.Polar

40、ity/ZeroDetectsignalswithrate(ontrol. 380ms to t 3 t7 Ir-IOOms-iI III +3.5V III -.- _. T-.- - r- I I Z.O. II Ir-: I I 1= , )III -1.5V Figure6.Polarity/ZeroDetectsignalswithnoratecontrol. 11 Tocheckthezero-detect.flip-flop,usealogicprobeoroscill(I(IJ)(ndnbs1( thepulsesontheoutputA6IC20pin 2.Thereshou

41、ldbeapuls(herforeach arnple.Ifnot,checktheinputtothisICandtheoutputfrUIHtllpulsetrln.f(lnller. Anothercheckforthepulsetransfornleroutputistoe-hcckthepo1:1rityflip-f1op .,;SIC11pin14shouldlternntcwithancativcinputandrcn1ailllowalwaysrtl!a IsitiCoutput. theanpIHi(.rsallcllC(kout,theonlyoUHrsignalstohe

42、c!H(lCdar(thp1(,(.1 :(ladries,pipe-tronicswitchandth(.polaritystro)(l. ReedRclys -:-.ereedrelaysthatarerequiredtooperateonDC,non-ratioarCgivenintable2. T;1etin1einteralsthataregivenarethetin1eperiodsthattherplaysareclosed. -:-1ereareotherrelaysthatareclosedoropendurintheentiresan1pleperiod, )utthese

43、relaysarenotincludedinthistable. RELAY K4orK5 K7 K8 K9 KIO,KII,orKI2 K14,K15 K17(WITH+POLARITY) K29 TABLE2. hisonlychecksthecoiland,ofcourse,thereedInaynotactuallybeclosin!:.A continuitycheckwilldetern1inethestateoftherelay.TheclosureofthesereIn.s 2retirnedwiththechargingcurve.Thebestwaytoseethatthe

44、relaydrivesarc .:ccurring-atthepropertinleistouseonetraceofanoscilloscopeontheIntegrator utputandtheothertraceonthe-reedrelay.Refcrtopage7-5intheOpcratin andServiceManual.ThevarioustilllinpointsontheIntegratorwaveformar ;:-ien.Also,thechartbelowtheInteratorWaveforn1ivesthetirningofallthe eedrelays.

45、ElectronicSwitch TheElectronicSvitchsignaliscoupledthroughthepulsetransfornlertotheA60 (inguardlogicboard.ThesignaloriginatesontheA6boardandattheinl)uttntlie 12 , II I, r r r f f Ir II I I I -,- - AGOboarditis0.511SCCpulse.Thispulseisus(dtotoletheGbinlri.s.(;J lIldG1areusedtocontroIdrivertransistors

46、A60Q1/Q2.TheoutputfrotHi(jO(1/Q2 urn,onandofftheFETswitchonA57circuitboard.Thebestwyto(Iu(kout thisircuitstostartattheoutputofA60Ql/Q2andke()ch0ekinghackuntiltl1( LIlltisfound.Alo.d(probewouldworkveryni(ly.ote,theO.5IJSC(pl1l(is Prydifficuittosecon:1nos(illoscope.Turning-up1I1(,intensitywillilllp. P

47、olarityStrou( T1Polar,Strobesinali.generatedinaln10stexactlythesamc111anncr th:tttl1. L.()ctronicSitchsignalisgenerated.Theonlydiffer(nceisthatthePularHy . t!obu_e _theG2igna1.Again,troubIeshooting- (ouldstartattheoutputoftile .GOcircuitboard,A60Q31,andproceedbacktothefault. F.:Raning.Therangingofyo

48、urinstrunlentcanbeconsideredintVOscctions u!111ude.First,andleastCOInplicated,isthenon-ratiornocte.Theothcr,1110r( (o111plicated111ode,isratiooperation.Ratioisnl0reconlplictfclbcc;luse.the rangechangesthreetinlesinoneratiosanlpleperiod:thefirst1ange(haneisto 111easureY,thesecondrangechangeistonleasurcX,andthefin;lchangehackto yrane. Tobegintroubleshootingtherangingcircuitsofthe3450A.setthefunctionsto HOLD,DC,andplaceashortacrosstheinput.Thefirstcheckwillbeofthe Prilnar y RangeBinares;PI,P2andP4onABIC2. ABIC3,