Fisher-FM190-tun-sm维修电路原理图.pdf

Service Manual THEFISHER THEFISHER -6 0 o: CT Ej,0, 0, ro,() :=. lRe.e BALANCE . 11I1111l I- FM-190X-190 RadioFans.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 TOOLSNEEDED The following are needed to completelytest and align modern high-fidelityinstruments such as amplifiers, tuners and receivers. Miscellaneous Adjustable-line-VoltageTransformeror line-voltageregulator Load Resistors (2) -8-ohm,50-watt (or higher) Stereo source (Turntablewith stereo cartridge or Tape Deck) Speakers (2) Full-range, for listeningtests Soldering iron (with small-diametertip). Fullyinsulated from power line. TestInstruments Vacuum-Tube VoltohmmeterDC VTVM Audio (AC) Vacuum-Tube Voltmeter(AC VTVM) Oscilloscope(Flat to lOOkcminimum) Audio(Sine-wave) Generator Intermodu lat ion AnaIyzer Sweep (FM) Generator (88 to 108 mc) Marker Generator MultiplexGenerator(preferablywithRF output- FISHER Model 300 or equal). Many of theitemsbelow are includedjustas a re- minder-they are normalprocedures, for experienced technicians.Shortcutscanbe takenbutoftenthey cause additionaldamage -to transistors,circuitcom- ponents or the printed-circuitboard. Soldering-Awell-tinned,hot, clean solderingiron tip willmake it easier to solderwithoutdamage to the printed-circuitboard or themany many circuitcom- ponentsmountedon it.It is not the wattage of the iron that counts -it is the heat availableat the tip. Low-wattage solderingirpns willoften take too long to heat a connection -pigtailleads will get too hot and damage the part. Too much heat, applied too long, will damage the printed-circuitboard. Some 50-wattirons reachtemperaturesof1,000 F-otherswillhardly meltsolder.Smalldiametertipsshouldbe used for singlesolder connections -largerpyramidand chisel tips are needed for larger areas. When removing defectiveresistors,capacitors,etc., theleads shouldbe cut as close to the body of the circuitcomponent as possible. (If the part is not being returnedfor in-warranty factory replacementit maybe cutinhalf -withdiagonal-cuttingpliers -tomake removal easier.) Specialde-solderingtipletsare made for unsolder- ingmultiple-terminalunitslikeIF transformersand electrolyticcapacitors.By unsolderingall terminalsat thesame timethepartcan be, removed withlittle chance of breakingthe printed-circuitboard. Always disconnectthe chassis from the power line when soldering.Turningthe power switchOFF is not enough. Power-line leakage paths, through the heating element,can destroy transistors. Transistors-Neverattempttodo any workon the transistoramplifierswithoutfirstdisconnectingthe - AC-power linecord -wait untilthe power supply filter- capacitorshave discharged. Guard againstshorts -it takes only an instantfor a base-to-collectorshort to destroy that transistorand possiblyothersdirect-coupledtoit.Inthe timeit takesfora droppedmachinescrew, washer or even the screwdriverrtoglance off a pair of socket terminals (or between a terminaland the chassis)a transistor can 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 be higher than the base-emitterbreakdown voltage of the transistor. OutputStage andDriver-Replacementsforoutput and driver transistors,if necessary, must be made from thesame beta group as the originaltype.The beta groupis indicatedby a colored dot on the mounting flangeof the transistor.Be sure toincludethisin- formation,when orderingreplacementtransistors. If one outputtransistorburns out (open or shorts), always remove all outputtransistorsin thatchannel and check the bias adjustment,the controland other parts in the network with an ohmmeter beforeinsert- ing a new transistor.Alloutputtransistorsinone channelwillbe destroyedif the base-biasingcircuit is open on the emitterend. When mountinga replacementpower transistorbe sure the bottom of the flange, the mica insulatorand the surface of the heat sink are free of foreign matter. Dust and gritcanprelentperfectcontact.Thisre- duces heat transferto the heat sink. Metallicparticles can puncturethe insulatorand cause shorts -ruining the transistor. Siliconegrease must be used between the transist- or and the mica insulatorand between the mica and theheat sinkforbest heat conduction.Heat is the grea,test enemy of electronicequipment.It can shorten thelifeof transistors,capacitorsand resistors.(Use Dow-Corning DC-3 or C20194 or equivalentcompounds made for power transistorheat conduction.) Use care when making connectionsto speakers and outputterminals.Any frayedwireendscancause shorts that may burn out the output transistors -they are direct-coupledto the speakers. There is no output transformer -nothing to limit current through the tran- sistors except the fuses. To reduce the possibilityof shortsat the speakers,lugs shouldbe used on the exposed ends -at lea,st the ends of the stranded wires shouldbe tinnedtopreventfrayedwireends.The currentin the speakers and outputcircuitry:is quite high. Any poor contactor small-sizewire,:,n cause power losses in the speaker system. Use 14 ojl16AWG for long runs of speaker-connectingwiring. DC-VoltageMeasurements-Thesebasic tests of the transistorcircuitryare made withoutthe signal gener- ator. Withoutany signal input measure the circuitvolt- ages -asindicatedontheschematic.The voltage differencebetween thebase and theemittershould be inthemi llivoltrange -a sensitiveDC meteris needed for these readings. A low-voltage range of 1volt, fullscale -or lower -is needed. Audio-Voltage(gain)Measurements-Theschematic andprinted-circuitboardlayout diagramsareused. Input signals are injectedat the proper points -found mostquicklyby usinglayoutoftheprinted-circuit board instead of the schematic.An AUDIO (AC) VTVM connectedto the test pointsshouldindicatevoltages close to those values shown in the boxes on the sche- matic.Many ot the signallevels in theinputstages are only a few millivolts-theycan not be read on the AC ranges suppliedon most Vacuum-Tube AC/DC Volt ohml!eters(VTVMs).Even with a l-voltrange a signal level of 100 millivolts(.1 volt)willbe the first1/10 of 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 of the springover the bottom eor in the frontnd drive-drum(with the drum rotatedto its extreme counterclockwiseposition). Stretchthe tensionspringuntil the loop on the free end sticksout of the s lot in the edge of the drive-drum.Now Insert a lengthof stiffwire, aboutl-inchlong(0pieceof straightened-outpaper clip will do nicely)throughthe loop .to keep the springstretchedwhilestringingthe dial cord. Placethe pieceof stiffwire in the outer groove of the drive-drumibridgingthe slotin the drivedrum. Tie a small,non-slip,loop in the end of the dial cord. iThreadthe loop in the dial cord throughthe openingin the driveo/lrum slot,under the spring,and hook the loop over 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 around the top guidepulley. Stretchthe dial cord to the left end of the dial,around th.nwoguide pulleysand then back to the fly-wheeldrive shaft. Wind 3 full turnsof dial cord aroundthe.driveshaft(as shown in the upper detaildrawing). While keepingth dial cord taut rotatethe drive-drumto TOINNEA GROOVE o TO OUTER GROOVE its extremeclockwiseposi tion and fit the clioI corcl into the remainingpulley. Set the dial cord in the outer grooveof the front-enddrive- drum and threadit throughthe loop in the end of the tension spring.(See detaildrawing.otlower right.) Pull all slackdial cord through the loop in the tension spring Check allpulleysfor proper threadingof the dial cord. Tie a smallknot in the dial cord to secureitto the loop in the tensionspring.(Use a tweezerwith a smalltip to help tie the knot.)Keep dial cord as tout as possiblewhile tying the knot. Apply a drop of quick-dryingcementto the knot to prevent it from slippingor becomingundone. After the cementhas dried completelypull out the piece of stiff wire and gentlylet the springcontractt9Q.pplytension to 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 place with a drop or two of quick.dryin,llcement. If replacement parts are out of stock, locally, they may be obtained directly from the Parts Department of FIStlER Radio Corporation. They will be shipped best way, either prepaid or C.O.D. unless otherwise specified. For instrument-operation information and technical assistance write Richard Hamilton, Customer Service Department,FISHERRadio Corporation,LongIsland City, NewYork 11101. RadioFans.CN 收音机爱 好者资料库 TROUBLESHOOTINGGUIDE When0defectoccursin On electroniccircuitthe first componentsuspectedis usuallythe vacuum tube. Many of the inexpensivetube testerswill not indicateall the possible internalfaultsin a voeuum tube - sli ght defectsoften sneak past thesetesters.It is better to substituteanothertube of the same type. Sometimesjt is possi ble to swi tch (transpose)tubesfrom one circuitto another.This .method of testingis most suitable when testinganindividualstereochannel.When a good tube is switchedwith0defectiveOne of the SOme type the symptom will beransferredfrom one stereochannelto the other. When substitutingtubesit is absolutelynecessaryto be certainthe tube beinginsertedis good - a new tube, from a fresh Iy openedcarton,is not necessariIy a perfecttube.De- fects ,an occur from shippingand handling. If you have any doubtsabout the qualityof a tube try it in an identicaleircuitthat is operatingproperly.For example, a tube with heoter-eathodeleakagemay operatenormallyin a circuitwith its cathodegrounded;transpOSe(switch)it with One in a circuitthat has a cathode-biasresistorand it will causea 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 the record player. Distortion Hum, Weak or No oudio 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. DistortIon Hum, Weak or No Cudia output (LEFTehonnelonly) SELECTORIn PHONO nod FM positions. Remove plug from Ll;FTRCRDR OUT jock,if used. Test(filamentleakagefor hum) Or substituteVI,V4,VS. Hum or No audio output (RIGHT channelonly) SELECTORin PHONO and FM positions. Remove plug from RIGHT RCRDR OUT jock,if used. Test(filamentleokagefor hum) or substituteVI,V4,V5. Hum orSELECTORin PHONO positionsonly No audio output J3, J7, J9 and theirplugs and interconnectingcablesto the recordplayer. Clean and tightenoil ground connections. ReverseAC line-cardplug in wall outlet ReverseAC line-eordplug from recordplayerin J18 (on chassis)if used. Hum or No audio output SELECTORin FM positiononly. Try other stations ReverseAC line.cordplug in wall outlet. Check:Antennaconnectionsand antenna(outdoor) Test(filamentleakagefor hum) or substituteVll,V12, V13, V14. Hum- No audio output DistortionCheck:Balancedmodulator0401and C409,C410; C407,C412iL401,L402. Test(filamentleakagefor hum) or substituteV401, V402. IS. V402, C406, R433,R434, R43S, CR402,CR401. Ali9nmentof Z421. RadioFans.CN 收音机爱 好者资料库 11131-2MULTIPLEXePRINTED CIRCUIT IT IR -, C412 470 (JJ 12KMPX GENERATOR. 180 1 r- I _J IA IALIGNMENTINSTRUCTIONSeMULTIPLEXSECTIONI ALTERNATEALIGNMENTPROCEDURE Formultiplex generator. without an RFoutput The pr.f.rredaHgnmentprocedure,in table1 below,ua multiplexSlen.ratorwith,an RF output,lik.the FISHERModel 300.Optiml:lmperformancewillb.obtainedonlywhenthe multiplexdecoderI.connectedto theFM detectorwithwhichitwillb.used.CheckIF alignmentirst-pooralignmentcanpreventpropermulti- plexdecoderoperation. Whenulingthisalignmentprocedure,iti.nec.uaryto disconnecttheratiodetectorfrom the multiplexdecoder ot the point where theoeneratori.connected.Unsold.rpoint1T carefully.The generatorinput mustb.through a simpl.low-passf1l r-o12 K resistorbetweenthemultipl.generatorand theMPX inputwithG180 pF.capa. citorfrom theMPX inputend of the r istorto ground(Figure2, on schematic). TESTEQUIPMENTREQUIRED:MULTIPLEXGENERATOR,AUDIO(AC)VTVM,100 kCOSCILLOSCOPEWITHEX. TERNALSWEEPJACKS,ALIGNMENTTOOL. TAILI Z TESTEQUIPMENTREQUIRED:MULTIPLEXGENERATOR,AUDIO<AC) VTVM.100 kCOSCILLOSCOPEWITH EX TERNALSWEEPJACKS,ALIGNMENTTOOL. TAIU 1 GENIIATOR INDICATOR ALIGNMENT IUPS CONN_CTIONAUDIO UVIL TVAND ADJUSTINDICATION CONNICTION CompOSite outputof 19 kc pilot100mV RMS 1 MPX generatorto AC,VTVM 21 top Qd bottomMaximumreadingon VTVM dem:cfvITfr ti1nt1) only(2S0MV poP)toTP0421 19 kc outptJtof o:ctlu:snro:-bgto 2 generatorto 01c1l10- Oscilloscopevertkol Scope horizontalInputl - Input to TP 422 ZZ38 kc. llSioloulpatternsee figurelJ generatornot etlnnected shouldbe as slow- toMPXsettlon movingas polble. AC VfVM andoscilloscope 3 SaM.01StepI 1000cps on0.7 V RMSvertlc:olInput to left ZItop Maximumreodingon VTVMl clean left dlannelonly13.92 V pPl:nonneloutputlug 1000 cps linewaveon os,IUoSope f.rmlnalJill 4 Sam.a. StepI 1000cps on0.7 V MS Some a$ Step 3 MPX leparatlon MlnlulatJn3b0bedbe right ehann.1only (3.92V PPl<:ontrol (R4. obtainedIn Step 3 VTVM (llid oscillos,op. Some VTVM readingQobtaln.din 5 Sameal Step1Sameal Step 4 0.7 V RMS. rticell Inputto rlahl 13.92 VpoP)ehonnaloutputlug- Step 3:!:2db; clean1000 cps sine terminallSI way.on (ncilioitope 6 JOOOcps on 0.7 V RMS MPX separation M:iul3n1bedSameas StepI I.ft chonnelonly (3.92V pP) Sam.e 05 Step 5 control(R41. ifneceualY-obtaInedin Step 5. GENEIATORINDICATORALIGNMENT ITIPS IFTYAND CONN.etIONMODULAtiON DIVIATIONCONHleTlON ADJUSTINDICATION 1 MUIrl:t=r:tor 19rvlfot 7.5kcVTVM to TP 21 21 top and MaximumreadIng:on VTVM onte.nnaterminal, bottom 19 kc outJIutof Verti<:Qllnputof osc!lIo- 0:c11:a;u:sndC:Zr:.!II;gto 2 generatorte osdllo KOPhorizontalInpvtl - scopetoA.22;set oscillo-ZZ38 kc. lInaiouspattern(see figure11 generotornot c:ollll.cf,dscopefor ell:ternol Iweepshouldbe as slow to MPX I.dlonmoving! en possible. Compo1teMPX, VTVM andosdllolcope oJ:n.r:C:eO:no3 verticalinput to righT Saas StepI1000r;pl on 75kc . channelOIJlput lug ZItop left r;hann.1only termlnal1RI 4 CompositeMPXr Same as Step 3 MPX separationMlnl:;U;:a03dJIt 0beZrnudbe Some as Step11000 cps on7Skr; control(R-4 right channelonlyobtainedIn Step3 VTVM andOIcilloteope Same VlVMreadingat obtainedIn 5