Fisher-FM190-tun-sm维修电路原理图.pdf

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1、Service ManualTHEFISHERTHEFISHER-60o:CTEj,0,0,ro,():=.lRe.eBALANCE.11I1111lI-FM-190X-190RadioFans.CN 收音机爱 好者资料库CAUT ION:This is a FISH ER precision high-fidelityin-strument.It should be serviced only by qualifiedpersonnel -trainedin therepair of transistorequipmentand printedcircuitry.EQUIPMENTAND T

2、OOLSNEEDEDThe following are needed to completelytest and align modern high-fidelityinstrumentssuch as amplifiers, tuners and receivers.MiscellaneousAdjustable-line-VoltageTransformerorline-voltageregulatorLoad Resistors (2) -8-ohm,50-watt (or higher)Stereo source (Turntablewith stereo cartridgeor Ta

3、pe Deck)Speakers (2) Full-range, for listeningtestsSoldering iron (with small-diametertip).Fullyinsulated from power line.TestInstrumentsVacuum-Tube VoltohmmeterDC VTVMAudio (AC) Vacuum-Tube Voltmeter(AC VTVM)Oscilloscope(Flat to lOOkcminimum)Audio(Sine-wave) GeneratorIntermodu lat ion AnaIyzerSweep

4、 (FM) Generator (88 to 108 mc)Marker GeneratorMultiplexGenerator(preferablywithRF output-FISHER Model 300 or equal).Many of theitemsbelow are includedjustas a re-minder-they are normalprocedures, for experiencedtechnicians.Shortcutscanbe takenbutoftentheycause additionaldamage -to transistors,circui

5、tcom-ponents or the printed-circuitboard.Soldering-Awell-tinned,hot, clean solderingiron tipwillmake it easier to solderwithoutdamage to theprinted-circuitboard or themany many circuitcom-ponentsmountedon it.It is not the wattage of theiron that counts -it is the heat availableat the tip.Low-wattage

6、 solderingirpns willoften take too long toheat a connection -pigtailleads will get too hot anddamage the part. Too much heat, applied too long, willdamage the printed-circuitboard. Some 50-wattironsreachtemperaturesof1,000 F-otherswillhardlymeltsolder.Smalldiametertipsshouldbe used forsinglesolder c

7、onnections -largerpyramidand chiseltips are needed for larger areas.When removing defectiveresistors,capacitors,etc.,theleads shouldbe cut as close to the body of thecircuitcomponent as possible. (If the part is not beingreturnedfor in-warranty factory replacementit maybecutinhalf -withdiagonal-cutt

8、ingpliers -tomakeremoval easier.)Specialde-solderingtipletsare made for unsolder-ingmultiple-terminalunitslikeIF transformersandelectrolyticcapacitors.By unsolderingall terminalsatthesame timethepartcan be, removed withlittlechance of breakingthe printed-circuitboard.Always disconnectthe chassis fro

9、m the power linewhen soldering.Turningthe power switchOFF is notenough. Power-line leakage paths, through the heatingelement,can destroy transistors.Transistors-Neverattempttodo any workon thetransistoramplifierswithoutfirstdisconnectingthe- AC-power linecord -wait untilthe power supply filter-capac

10、itorshave discharged.Guard againstshorts -it takes only an instantfora base-to-collectorshort to destroy that transistorandpossiblyothersdirect-coupledtoit.Inthe timeittakesfora droppedmachinescrew, washer or eventhe screwdriverrtoglance off a pair of socket terminals(or between a terminaland the ch

11、assis)a transistorcan be rllined.DO NOT bias the base of any transistorto, or near,the same voltage appl ied to its collector.DO NOT use an ohmmeterfor testi ng transistors.The voltageappliedthroughthe testprobes may behigher than the base-emitterbreakdown voltage of thetransistor.OutputStage andDri

12、ver-Replacementsforoutputand driver transistors,if necessary, must be made fromthesame beta group as the originaltype.The betagroupis indicatedby a colored dot on the mountingflangeof the transistor.Be sure toincludethisin-formation,when orderingreplacementtransistors.If one outputtransistorburns ou

13、t (open or shorts),always remove all outputtransistorsin thatchanneland check the bias adjustment,the controland otherparts in the network with an ohmmeter beforeinsert-ing a new transistor.Alloutputtransistorsinonechannelwillbe destroyedif the base-biasingcircuitis open on the emitterend.When mount

14、inga replacementpower transistorbesure the bottom of the flange, the mica insulatorandthe surface of the heat sink are free of foreign matter.Dust and gritcanprelentperfectcontact.Thisre-duces heat transferto the heat sink. Metallicparticlescan puncturethe insulatorand cause shorts -ruiningthe trans

15、istor.Siliconegrease must be used between the transist-or and the mica insulatorand between the mica andtheheat sinkforbest heat conduction.Heat is thegrea,test enemy of electronicequipment.It can shortenthelifeof transistors,capacitorsand resistors.(UseDow-Corning DC-3 or C20194 or equivalentcompou

16、ndsmade for power transistorheat conduction.)Use care when making connectionsto speakers andoutputterminals.Any frayedwireendscancauseshorts that may burn out the output transistors -theyare direct-coupledto the speakers. There is no outputtransformer -nothing to limit current through the tran-sisto

17、rs except the fuses. To reduce the possibilityofshortsat the speakers,lugs shouldbe used on theexposed ends -at lea,st the ends of the stranded wiresshouldbe tinnedtopreventfrayedwireends.Thecurrentin the speakers and outputcircuitry:is quitehigh. Any poor contactor small-sizewire,:,n causepower los

18、ses in the speaker system. Use 14 ojl16AWGfor long runs of speaker-connectingwiring.DC-VoltageMeasurements-Thesebasic tests of thetransistorcircuitryare made withoutthe signal gener-ator. Withoutany signal input measure the circuitvolt-ages -asindicatedontheschematic.The voltagedifferencebetween the

19、base and theemittershouldbe inthemi llivoltrange -a sensitiveDC meterisneeded for these readings. A low-voltage range of 1volt,fullscale -or lower -is needed.Audio-Voltage(gain)Measurements-Theschematicandprinted-circuitboardlayout diagramsareused.Input signals are injectedat the proper points -foun

20、dmostquicklyby usinglayoutoftheprinted-circuitboard instead of the schematic.An AUDIO (AC) VTVMconnectedto the test pointsshouldindicatevoltagesclose to those values shown in the boxes on the sche-matic.Many ot the signallevels in theinputstagesare only a few millivolts-theycan not be read on theAC

21、ranges suppliedon most Vacuum-Tube AC/DC Voltohml!eters(VTVMs).Even with a l-voltrange a signallevel of 100 millivolts(.1 volt)willbe the first1/10of the meter scale. A reading of 1 millivolt(.001 volt)willhardly even move the meter needle.RadioFans.CN 收音机爱 好者资料库DIAL STRINGINGPROCEDURE Hook one end

22、of the springover the bottom eor in thefrontnd drive-drum(with the drum rotatedto its extremecounterclockwiseposition).Stretchthe tensionspringuntil the loop on the free endsticksout of the s lot in the edge of the drive-drum.NowInsert a lengthof stiffwire, aboutl-inchlong(0pieceofstraightened-outpa

23、per clip will do nicely)throughthe loop.to keep the springstretchedwhilestringingthe dial cord.Placethe pieceof stiffwire in the outer groove of thedrive-drumibridgingthe slotin the drivedrum.Tie a small,non-slip,loop in the end of the dial cord.iThreadthe loop in the dial cord throughthe openingint

24、he driveo/lrum slot,under the spring,and hook the loopover the top ear insidethe drive drum. Wrap the dial cord around the clrive-drum(counterclock-wise)about*of a turn,in the innergroove,ond then aroundthe top guidepulley. Stretchthe dial cord to the left end of the dial,aroundth.nwoguide pulleysan

25、d then back to the fly-wheeldriveshaft.Wind 3 full turnsof dial cord aroundthe.driveshaft(asshown in the upper detaildrawing). While keepingth dial cord taut rotatethe drive-drumtoTOINNEAGROOVEoTO OUTERGROOVEits extremeclockwiseposi tion and fit the clioI corcl intothe remainingpulley.Set the dial c

26、ord in the outer grooveof the front-enddrive-drum and threadit throughthe loop in the end of the tensionspring.(See detaildrawing.otlower right.)Pull all slackdial cord through the loop in the tensionspring Check allpulleysfor proper threadingof the dial cord.Tie a smallknot in the dial cord to secu

27、reitto the loopin the tensionspring.(Use a tweezerwith a smalltip tohelp tie the knot.)Keep dial cord as tout as possiblewhiletying the knot.Apply a drop of quick-dryingcementto the knot to preventit from slippingor becomingundone.After the cementhas dried completelypull out the pieceof stiff wire a

28、nd gentlylet the springcontractt9Q.pplytensionto the dial cord.:.:.Rotat.the frontenddrive-drumta its extremetbunter-clockwiseposition.Settheclial pointerto the zero (0) calibrationon the log-ging sealeof the s Iide. uIe cliol.Attach.thepointerto the dial cord and cementit in placewith a drop or two

29、 of quick.dryin,llcement.If replacement parts are out of stock, locally, they may be obtaineddirectly from the Parts Department of FIStlER Radio Corporation.They will be shipped best way, either prepaid or C.O.D. unlessotherwise specified.For instrument-operation information and technical assistance

30、 writeRichard Hamilton, Customer Service Department,FISHERRadioCorporation,LongIsland City, NewYork 11101.TROUBLESHOOTINGGUIDEWhen0defectoccursin On electroniccircuitthe firstcomponentsuspectedis usuallythe vacuum tube. Many ofthe inexpensivetube testerswill not indicateall the possible internalfaul

31、tsin a voeuum tube - sli ght defectsoften sneakpast thesetesters.It is better to substituteanothertube ofthe same type.Sometimesjt is possi ble to swi tch (transpose)tubesfromone circuitto another.This .method of testingis most suitablewhen testinganindividualstereochannel.When a good tubeis switche

32、dwith0defectiveOne of the SOme type the symptomwill beransferredfrom one stereochannelto the other.When substitutingtubesit is absolutelynecessaryto becertainthe tube beinginsertedis good - a new tube, from afresh Iy openedcarton,is not necessariIy a perfecttube.De-fects ,an occur from shippingand h

33、andling.If you have any doubtsabout the qualityof a tube try itin an identicaleircuitthat is operatingproperly.For example,a tube with heoter-eathodeleakagemay operatenormallyin acircuitwith its cathodegrounded;transpOSe(switch)it withOne in a circuitthat has a cathode-biasresistorand it willcausea

34、lot of hum.AC-interloekplugand,.,eket,power cord and plug. walloutlet.Automaticshutffswitch51 (part of SELECTORswitch)Power switch54.Automaticshut-offswitch51 (part of SELECTORswitch). J9 and its plug and the interconnectingcableand the turntableswitchon therecord player.DistortionHum, Weak orNo oud

35、io outputCheck: SPKR switchpositionand its operation.Testor.substituteVI.Testfor proper DC voltagesat: CR2, C2, R3; R3, R6, C3B; R6, R7, C3C;R7, C3D.Settingof HUM ADJUST CONTROL(R2).29S-voltDC power supplyfi Iter (C3A,B, C, 0 ),Bios supply(CR3 and C4) for AC ripple.DistortIonHum, Weak orNo Cudia out

36、put(LEFTehonnelonly) SELECTORIn PHONO nod FM positions.Remove plug from Ll;FTRCRDR OUT jock,if used.Test(filamentleakagefor hum) Or substituteVI,V4,VS.Hum orNo audio output(RIGHT channelonly) SELECTORin PHONO and FM positions.Remove plug from RIGHT RCRDR OUT jock,if used.Test(filamentleokagefor hum)

37、 or substituteVI,V4,V5.Hum orSELECTORin PHONO positionsonlyNo audio outputJ3, J7, J9 and theirplugs and interconnectingcablesto the recordplayer.Clean and tightenoil ground connections.ReverseAC line-cardplug in wall outletReverseAC line-eordplug from recordplayerin J18 (on chassis)if used.Hum orNo

38、audio outputSELECTORin FM positiononly.Try other stationsReverseAC line.cordplug in wall outlet.Check:Antennaconnectionsand antenna(outdoor)Test(filamentleakagefor hum) or substituteVll,V12, V13, V14.Hum-No audio outputDistortionCheck:Balancedmodulator0401and C409,C410; C407,C412iL401,L402.Test(fila

39、mentleakagefor hum) or substituteV401, V402.IS. V402, C406, R433,R434, R43S, CR402,CR401. Ali9nmentof Z421.11131-2MULTIPLEXePRINTED CIRCUITITIR-,C412470(JJ12KMPXGENERATOR.1801r-I_JIAIALIGNMENTINSTRUCTIONSeMULTIPLEXSECTIONIALTERNATEALIGNMENTPROCEDUREFormultiplex generator. without an RFoutputThe pr.f

40、.rredaHgnmentprocedure,in table1 below,ua multiplexSlen.ratorwith,an RF output,lik.theFISHERModel 300.Optiml:lmperformancewillb.obtainedonlywhenthe multiplexdecoderI.connectedtotheFM detectorwithwhichitwillb.used.CheckIF alignmentirst-pooralignmentcanpreventpropermulti-plexdecoderoperation.Whenuling

41、thisalignmentprocedure,iti.nec.uaryto disconnecttheratiodetectorfrom the multiplexdecoderot the point where theoeneratori.connected.Unsold.rpoint1T carefully.The generatorinput mustb.througha simpl.low-passf1l r-o12 K resistorbetweenthemultipl.generatorand theMPX inputwithG180 pF.capa.citorfrom theM

42、PX inputend of the r istorto ground(Figure2, on schematic).TESTEQUIPMENTREQUIRED:MULTIPLEXGENERATOR,AUDIO(AC)VTVM,100 kCOSCILLOSCOPEWITHEX.TERNALSWEEPJACKS,ALIGNMENTTOOL.TAILI ZTESTEQUIPMENTREQUIRED:MULTIPLEXGENERATOR,AUDIOAC) VTVM.100 kCOSCILLOSCOPEWITH EXTERNALSWEEPJACKS,ALIGNMENTTOOL.TAIU 1GENIIA

43、TORINDICATORALIGNMENTIUPSCONN_CTIONAUDIOUVILTVANDADJUSTINDICATIONCONNICTIONCompOSite outputof19 kc pilot100mV RMS1MPX generatortoAC,VTVM21 top Qd bottomMaximumreadingon VTVMdem:cfvITfr ti1nt1)only(2S0MV poP)toTP042119 kc outptJtofo:ctlu:snro:-bgto2generatorto 01c1l10-OscilloscopevertkolScope horizon

44、talInputl-Input to TP 422ZZ38 kc. llSioloulpatternsee figurelJgeneratornot etlnnectedshouldbe as slow-toMPXsettlonmovingas polble.AC VfVM andoscilloscope3SaM.01StepI1000cps on0.7 V RMSvertlc:olInput to leftZItopMaximumreodingon VTVMl cleanleft dlannelonly13.92 V pPl:nonneloutputlug1000 cps linewaveo

45、n os,IUoSopef.rmlnalJill4Sam.a. StepI1000cps on0.7 V MSSome a$ Step 3MPX leparatlonMlnlulatJn3b0bedberight ehann.1only(3.92V PPl:ontrol (R4.obtainedIn Step 3VTVM (llid oscillos,op.Some VTVM readingQobtaln.din5Sameal Step1Sameal Step 40.7 V RMS. rticell Inputto rlahl13.92 VpoP)ehonnaloutputlug-Step 3

46、:!:2db; clean1000 cps sineterminallSIway.on (ncilioitope6JOOOcps on0.7 V RMSMPX separationM:iul3n1bedSameas StepII.ft chonnelonly(3.92V pP)Sam.e 05 Step 5control(R41.ifneceualY-obtaInedin Step 5.GENEIATORINDICATORALIGNMENTITIPSIFTYANDCONN.etIONMODULAtiONDIVIATIONCONHleTlONADJUSTINDICATION1MUIrl:t=r:

47、tor19rvlfot7.5kcVTVM to TP 2121 top andMaximumreadIng:on VTVMonte.nnaterminal,bottom19 kc outJIutofVerti:Qllnputof osc!lIo-0:c11:a;u:sndC:Zr:.!II;gto2generatorte osdlloKOPhorizontalInpvtl-scopetoA.22;set oscillo-ZZ38 kc. lInaiouspattern(see figure11generotornot c:ollll.cf,dscopefor ell:ternol Iweeps

48、houldbe as slowto MPX I.dlonmoving! en possible.Compo1teMPX,VTVM andosdllolcopeoJ:n.r:C:eO:no3verticalinput to righTSaas StepI1000r;pl on75kc. channelOIJlput lugZItopleft r;hann.1onlytermlnal1RI4CompositeMPXrSame as Step 3MPX separationMlnl:;U;:a03dJIt 0beZrnudbeSome as Step11000 cps on7Skr;control(

49、R-4right channelonlyobtainedIn Step3VTVM andOIcilloteopeSame VlVMreadingat obtainedIn5Same as Stp1Same as Step 475kcverticalinputtolrlght-Step 3 :2dblclean1000 cps sin.channeloutputlugwaveon oscilloscope(terminalIS)6CompositeMPX;MPX separationM:I;U;:a(ltJ3bbefndSame as Step 11000 cps on75kcSame01 St

50、ep 5controlR41.left dlaMelonlyif nec.nary-obtainedIn Steps.,IlOOk.IIIL_-81 SELECTORSWITCHIOFF-SHOWNINFM MONOMSTEREOFlI STEREOF1LTEIt.I. 10111 ALl.VOLTAt!MID(:UMINTMtASUltEM!NT InL.IM!VOLTAGIT01l1VAC.t.DC VOLTEMIAIUftitlWITHDC lTVTO eI!SltITHNO atONALINPUT.lIl.lCTOfl ITCK INMMONOOIITION.TUIlt1l,OWlRC