Realistic-STA21-rec-sm 维修电路原理图.pdf

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1、STA.21AM /FM STEREO RECETVERCatalog Number : 31 -2071cusT0M MANUFACTURED FOR RAD|0 SHACK ln DMS|0N 0F TANDY C0RP0RAT|0NJRadioFans.CN 收音机爱 好者资料库(1 ELECTRICAL PERFORMANCE SPECIFICATIONS . 3 -(2 DISASSEMBLY INSTRUCTIONS .(3) BLOCK DIAGRAM(4) ALIGNMENT INSTRUCTIONS .,. 7 -(5) TROUBLE SHOOTING . . , 12 -

2、(6) DIAL STRINGING DIAGRAM(7) IC & TRANSISTOR LEAD IDENTIFICATION .(8) AM/FM TUNER, IF & MPX ASSEMBLED BOARD(TOP & BOTTOM VIEWS)(9) PRE & TONE AMP ASSEMBLED BOARD(TOP & BOTTOM VIEWS)(10) MAIN AMP & POWER SUPPLY ASSEMBLED BOARD(TOP & BOTTOM V|EWS) . 18(11) JACK ASSEMBLED BOARD(TOP & BOTTOM VTEWS) . 1

3、9(12) ELECTRICAL PARTS LIST . , . ,. 19 - 27(13) EXPLODED VIEW PARTS LIST . 28 - 30(14) IC INTERNAL DIAGRAM . 31(15) SCHEMATIC DIAGRAM . 32 - 33(16) EXPLODED VIEW 34 - 3545b111415151617-2-RadioFans.CN 收音机爱 好者资料库1. ELECTRICAL PERFORMANCE SPECIFICATIONSAM BANDRangeIFAntenna Sensitivity for S/N 20 dBat

4、 600 kHzat 1000 kHzat 1400 kHzTerminal Sensitivity (20 dB S/N)ACA at S/N 6 dB sensitivity at 1000 kHzAGC Distortion at 1000 kHz, 100 mV/m, 80% Mod.AGC Figure of MeritlF Rejection at 600 kHzlmage Rejection at 1400 kHzDistortion at 5 mV/m 30% Mod.Tapeout Level at 5 mV/m 30o/o Mod. 400 HzFidelity 5 mV/

5、m lnput, -6 dB Down (1 kHz:0 dB)Whistle Modulation of 2nd and 3rd Harmonicatland5mV/mCalibration Accuracy at 600 kHzat 1400 kHzFM BANDRange (For UL and C.S.A. Models)Range (For European and Australian Models)IFIHF Sensitivity at 90, 98 and 106 MHzFM S/N Ratio at 98 MHz, 1 mV lnputFM Limiting -3 dBlF

6、 Rejection at 90 MHzlmage Rejection at 106 MHzCapture RatioACA + 400 kHz at 100 pVAudio THD 400 H2,75 kHz Dev.Audio THD 400 H2,22.5 kHz Dev.Calibration Accuracy at 90 MHzat 106 MHzAFC Holding Range with 1 mV SignalAM SuppressionMaximum Signal Handling CapacityTapeout Level 1 mV 75 kHz Dev. 400 Hz Mo

7、d.All Sets must meet the Requirements of the FCC.UNIT(kHz)(kHz)I pV /ml( zV)(dB)(o/ol(dB)(dB)(dB)l/ol(mV)(Hz) 50(o/ol(kHz)(kHz)UNIT(MHz)(l.VlHz)(MHz)( pYl(dB)( pV)(dB)(dB)(dB)(dB)lo/ol(o/ol(kHz)(kHz)(kHz)(dB)(v)(mV)NOM INAL510 - 1650455200200200102844532451.5250- 2500LIMIT520 - 1620500500s00NOMINAL

8、LIMIT86.5 - 108.5 88 - 10887.5 - 108.5 87.5 - 10810.72.8603.280503450.50.3+ 200380.275020103827353.520010t25+50;:;557.170456301.00.8t 500+ 500300 - 800300.1750 + 2.5 dB:Frequency Response must meet the 75 1-usec.De-emphasis for UL and C.S.A. Approved Models(50 p sec.De-emphasis for European and Aust

9、ralian Models).-3-FM MPXStereo lndicator ON PointSeparation at 1 mV 100 Hz1 kHz10 kHzStereo Distortion 1 mV 1 kHz38 kHz RejectionSCA RejectionAUDIO SECTIONlnput lmpedance PHONO MAG.AUXOutput Power at THD 1% 8 ohmsBoth Channels Driven at 1 kHzPower BandwiEooIo;ooododo$o;or2zzzzZzFz-O-O6HHdoOFE)z!d1AO

10、IriOF-zzoou=!2orHrl=EoL=Eu=o22tUFF=!2?3uF:5=*Lo9_c-6-4. ALIGNMENT INSTRUCTIONSMAIN AMPLIFIER AND RESET CIRCUIT ADJUSTMENT/CHECKNOTE o Maintain line voltage at 120 volts. (UL, C.S.A.) (Use 220/240 VAC For European & Australian Models.)o Set SELECTOR Switch to AUX. Set MODE Switch to STEREO.o See P.C.

11、B. illustrations for alignment points/adjustments.MAIN AMPL!FIER ADJUSTMENTSTEPADJUSTMENTEOUIPMENTCONNECTIONAUDIO FREO.LEVELADJUSTMENT1Check DC Balanceby measuringDC voltageacross Outputof L andR channel.DC Volt MeterSee Fig. 1No signalDCvoltageshould beless than30 mV.Select of8305(L channel)R306(R

12、channel)2ldling currentadjustmentDC Volt MeterSee Fig,2No signalAdjust voltageacross Emitterresistors R321and R322to 10 mV.(8 0 Load)R329R3300-30 mVMain AmpFigure 1 (-30 mV to +30 mV)Reset Lamp8 ohm loadSpeaker OutputOscilloscope(When protector circuit is activated)EOscilloscopeOscHz)Adjust Volt Met

13、er for 10 mVMain AmPFigure 2RESET CI RCU IT ADJ USTM ENTSTEPADJUSTMENTEOUIPMENTCONNECTIONAUDIO FREO.SETTINGLEVELADJUSTMENT1Turn trimmer resistor R 332 counterclockwise (minimum value).2Audio Osc.V.T.V.M.Figure 31000 HzVOLUME: MaxBASS, TREBLE& BALANCE:CenterAdjust input toAUX 1 to getoutput levelof a

14、bout 3 Volts(8 ohm load)3Reset circuitadjustmentAudio Osc.V.T.V.M.Figure 41000 HzSame asaboveAdjust R 332 sooutput drops to zero(RESET comes on)when output speakerterminals are shorted:DO NOT ADJUSTPAST THIS POINT.R 332Figure 3-7 -AC V.T.V.M. (3V)Figure 4l-o oou(TC 1O3)FM OSC, TRIMMERmAN_r%3i*,ta_El

15、f- FM lsr lF rr rolrALIGNMENTSignal generator output should be no higher than necessary to obtain an output reading.Maintain line voltage at 120 volts. UL, C.S.A. (Use 220/240 VAC For European & Australian Models.)Set SELECTOR Switch to AM.See P.C.B. illustrations for alignment points/adjustments.AM

16、 ALIGNMENT SET-UPAM INTERNAL BAR ANTENNAScopeFigure 5-8-EOUIPMENT REOUIRED1. AM Signal Generator2. AC Voltmeter3. OscilloscopeAM IF&NOTES:TUNER COILrrc 101) (rc 104FM ANT AM ANTTRIMMER TRIMMER& TRIMMER LOCATIONS(TC 102) (TC 1O5)FM RF AM O$,TRIMMER TRIMMERRFaoaaSTEPSIGNAL GENERATORCOUPLINGSIGNAL GENE

17、RATORFREOUENCYDIAL SETTINGINDICATORADJUSTMENTREMARKS1Connect standardloop ANTENNA toSignal Generatorand radiate signalinto the AM Ferriteantenna. See Fig. 5.455 kHz(4ob Hz,30% MoD)Point of non-interference(near 600 kHz)AC VoltmetertO TAPE OUTJACKT 1061 107T 108T 109Adjust formaximumreading.2Same as

18、above600 kHz (400 Hz,30o/o MOD)600 kHzSame as aboveT 105 (OSC Coil)L 106 (AM ANTCoil)Adjust formaximumreading.3Same as above1400 kHz (400 Hz,30o/o MOD)1400 kHzSame as aboveTC 105(OSC Trimmer)TC 104(ANT Trimmer)Adjust formaximumreading.4Repeat steps 2 and 3 urrtil no further change is noticed.5Same a

19、s step l1000 kHz (400 Hz,30% MOD)Output levelto 100 mV,/mPoint of non-interferenceand no signalAM StrengthMeterSelectvalue ofR 160Meter Pointeron Receivershould indicatebetween 80o/oand 90% onthe Meter.AM SIGNAL GENERATOR2(60cm)-tlr)rACVOLTMETE RCf)B-.=-rE!-=STA-21TAPE OUT (L or R)FM RF & IF ALIGNME

20、NTEOUIPMENT REOUIRED 3. AC Vottmeter1. FM signal Generator output Level: 1 mV 4. oscilloscope2. Sweep Generator S. Distortion MeterNOTE o Signal Generator output should be no higher than necessary to obtain an output reading. Set SELECTOR Switch to FM.o Maintain Line voltage at 12Q volts. (UL, C.S.A

21、.) 1220/240 VAC For European & Australian Models.)a Refer to P.C.B. illustrations for test points,/adjustments.STEPGENERATORCOUPLINGGENERATORFREOUENCYRADIO DIALSETTINGINDICATORADJUSTMENTREMARKS1Sweep Generator toFM ANT terminalon FM Front endboard10.7 MHz(1400 kHzSweep)Any dial settingwhere no noise

22、or interferenceexistsScope to TP 7at R 151MPX input)AM/FMIMPXBoardT 101, 102103, 104(Primary)FM IFTAdjust for maximumamplitude andproper linearitybetween + 150 kHzmarkers.Refer to Fig. 7.2Sweep Generator toFM AntennaTerminal thru FMDummy antenna(300 ohm)T101, 102FM IFT3Same as aboveT 104 FM IFT.(Pri

23、mary andSecondary)Ajust for symmetri-cal S curve asshown in Fig.6.4Signal Generator toFM AntennaTerminal thru FMDummy antenna(300 ohm)98 MHz(400 Hz, 100o/oMODTune forMaximumreading onmeterDistortionMeter to TAPEOUT JackT 104FM Discrim.(Secondary)Adjust for minimumdistortion.5Same as above*86.5 MHzSe

24、e Notein step 7Tuning gangfully closedAC Voltmeterand Scope toTAPE OUTJackL 105(FM OSCAdjust for maximumreading on meter.6Same as above108.5 MHzTuning gangfully openedTC 103 (FMOSC Trimmer)7Repeat STEPs (5) and (6) until Tuning Range Covers exactly from 86.5 MHz to 108.5 MHz.(*European models must n

25、ot be able to tune below 87.8 MHz.)8Signal Generator toFM Dummyantenna (300 ohm)90 MHz90 MHzTune toSignalAC Voltmeterand Scope toTAPE OUTJackL 101(FM ANT Coil)L 103 (FM BFCoil; stretchor squeeze)Adjust for maximumreading on meter.9Same as above106 MHz106 MHzTune toSignalTC 101 (FMANT Trimmer)TC 102

26、(FMRF Trimmer)10Repeat STEPs (8) and (9) until no further improvement is noticed.11Same as STEP (8)ANT. input: 1 mV98 MHz98 MHz Tune toSignalT110Adjust for maximumreading on meter.12Same as STEP (8)ANT. input: 100 mVVR1OlAdjust so the MeterPointer on Receiveris full scale.-9-FM SIGNAL GENERATORFM AL

27、IGNMENT SET-UP3OOO DUMMY FM ANTSweep Gen-FM STEREO ALIGNMENTEquipment Required1. Stereo Modulator . . . .2. FM Signal Generator . .3. Audio Generator4. AC Voltmeter5. Oscilloscope6. Distortion Meter7. Frequency CounterNote: See P.C.B. illustration for alignment/test points.PreliminariesSet SELECTOR

28、switch to FM STEREO.MULTIPLEX & SEPARATION ALIGNMENTTAPE OUT(L or B)AC V.T.V-M-DISTOBTION METERtLrpTatRlsl(470)Figure 7Connect Stereo Modulator to EXT. Mod. terminal FM signal generator.Modulation Level of 19 ktz Pilot Signal .8 - 10 %Output Level . 1 mVFrequency . Approximately 98 MHzDeviation .75

29、kHz 100 % modulation of composite signalSTEPSIGNAL GENERATORCOUPLINGSTEREOMODULATIONINDICATORADJUSTMENTREMARKS1Connect to FM Antennaterminal thru FMdummy antenna(30O 0 )Mono. 1 kHz1000 Hz, No Mod)lnput 1 mVCounter connectedto TP 14 at Pin No 12of lCVR 103Adjust for 19 kHz+50 Hz on Counter.Refer to F

30、ig. 8.2Same as aboveComposite MPXSignal 1 kHz onLeft channel ONLYAC Voltmeterconnected forTAPE OUTjack of RightchannelVR 102(Separation)Adjust for mini-mum reading.Refer to Fig. 9.3Same as aboveComposite MPXSignal 1 kHz onRight channel ONLYAC Voltmeterconnected forTAPE OUTjack of leftchannelSame as

31、aboveSame as above4Repeat STEPs 2 and 3 until AC Voltmeter reading is at least -33 dB re same channel output (i.e.33 dB separation).5Same as step 1CompositeSignal 1 kHzAC Voltmeterconnected toTAPE OUTjackWith 10 pVantenna input signal,stereo indicatorlamp should come on.- 10-TP 14161514131211109rc 1

32、01 LA 33501 23 4 5 6 7 AFM STEREO ALIGNMENT SET-UPFM ANTTERMINALTAPE OUTJACKFigure 8Figure 9BRIEF DESCRIPTION OF PROTECTIVE CIRCUITlf speaker terminals are shorted, or Load impedance of one channel (Left or Right) comes lessthan 4 ohms, excessively high current flows from Emitter to Collector of TR

33、313 (or TR 314) anda high voltage appears across R 323 (or R3241.This high voltage goes to Gate of SCR D315 after being rectified by D 308 (or D 309). When thevoltage between Cathode and Gate increases to about 0.7 V, SCR D315 will be turned on.Voltageat Pin No. 15on PowerSupply Board goesto -1 V to

34、 0V, PRE AMP and TONE circuitswill stop functioning and thus protect MAIN Amp.lf this should occur, the amplifier will automatically shut down and output will drop to zero. Turnthe receiver off to reset the protective circuit.When the problem is corrected, turn the receiver on again.TR 3II(TR 3t2)R

35、321( R 322)R 333R 332 C 3t9POWER SUPPLY CIRCUITPRE & TONE B+D3o8 ; a(D3oe) I itIOUT PUTLor RMAIN AMP CIRCUIT- 11-5. TROUBLE SHOOT!NGSymptomCause/Remedy1) No output.1) Faulty AC power cord. Replace the cord.2) Defective power switch.x Replace the switch.3) Broken wire in the power transformer.* Repla

36、ce the transformer.2) Pilot lamp does not light.1) Broken lamp.x Replace the lamp.2) Open in the power transformer tertiary winding. Replace the power transformer.3) Pilot lamp lights but no speaker ouptut.1) Defective capacitor C326or C327.* Replace the defective capacitors).2) Defective diode D 30

37、1, 302, 303 or 304.x Replace the defective diode(s).3) Defect in the power transformer secondary winding.* Beplace the power transformer.4) Blows fuse.1) Defective doide D 301-304 in the rectifier circuit.x Replace the defective diode(s).2) Short-circuit in the rectifier circuit.x Remove the short.3

38、) Short-circuit in power transistor circuitry TR 311-314.* Repair circuit and,/or Replace the defective transistor.5-1) No output one channel with VOLUMEat maximum and BALANCE at center,when a test signal is appliedto the terminal of non-operatingchannel of the BALANCEcontrol R 249.1) Defective tran

39、sistor TR 205, 206 or TR 301-314.x Replace the defective transistor(s).2) Defective resistor or capacitor of TONE or MAIN AMP circuit.* Replace the defective part(s).5-2) No output when a test signal is appliedto the input terminals.1) Defective transistor, resistor or capacitor of PRE AMP circuit.*

40、 Replace the defective part(s).2) Defective MONO/STEBEO or TAPE MONITOR switch.x Replace or repair the switch(es).3) Defective Selector switch,* Replace the Selector switch.6) Speaker works normally but headphonedoes not work.1) Defective R zl01 (left) or R 4O2 (right).x Change it.7) All the inputs

41、work normally exceptAUX input.1) Poor contact in AUX input jack.x Replace or repair it.2) Defective resistor R 501, 502, 503 or 5(X.* Replace it.3) Poor contact in selector switch.* Repair or replace the switch.8) PHONO input no operative.1) Poor contact in PHONO input jack.x Repair or replace it.2)

42、 Faulty selector switch.x Repair or replace the switch.- 12-SymptomCause/Remedy9) TAPE OUT inoperative.1) Poor contact in TAPE OUT ouput jack.*. Repair or replace it.10) No AM or FM.(TUNER B + voltage is not l1-12 V).1) Broken tertiary winding in the power transformer.* Replace the transformer.2) De

43、fective diode D 305,306 or D314.* Change the defective diode(s).3) Faulty capacitor C 3n,324, or 325.x Change it.4) Defective resistor R 337.* Replace the resistor.5l Zener diode D 314 defective.* Replace the diode.6) Short circuit in TUNER B + circuit.* Remove the short.7) Poor contact in selector

44、switch.* Repair or replace it.11) No FM.1) Poor contact in selector switch.x Repair or replace it.2) Defective resistor or capacitor of FM Tuner circuit.* Replace the defective part(s).3) Transistor, diode, lFT, resistor or capacitor ofFM Tuner & lF board defective.* Replace the defective part(s).4)

45、 Faulty FM Antenna lead-in/circuitry.* Repair or replace the Antenna lead-in,/circuitry.12) No AM.1) Poor contact in selector switch. Repair or replace the switch.2) Transistor, diode, lFT, resistor or capacitor of AM lF defective.* Replace the defective part(s).3) Bar-Antenna coil defective.* Repai

46、r or replace it.13) No MPX separation.1 ) lmproper adjustment.x Readjust it.2) lC of MPX board defective.x Replace the lC.3) VR 102 or 103 (Trimmer resistor) defective.x Replace it.14) No stereo light.1) STEREO Lamp burned out.* Replace the lamp.2) Defective lC of MPX board. Change the defective lC.

47、15) FM STEREO does not works.1) Defective lC (LA 3350).x Replace it.2) Defective VR 102 or 103.x Replace it.3) Defective transistor, resistor, capacitor or diode ofFM MPX circuit.x Replace the defective part(s).4) Defective STEREO lamp PL 5.x Replace it.- 13-SymptomCause/Remedy16) LOUDNESS has no ef

48、fect.1) Defective LOUDNESS switch.x Replace the switch.2) Defective C 219, 220, 221, )r?, R 245 or R 246.x Replace the defective part(s).17) BASS has no effect.1) R 251 (100K BASS control) defective.x Replace it.2) Def ective R 237, 238, 239, 240, 241, 242, C 235, 236, 231 or238 of Tone Control Boar

49、d.x Replace the defective part(s).18) TREBLE has no effect.1) Faulty R 250 (100K TREBLE control).* Replace it.2) Defective C 231,232,233,234, R 2(l or 24 ot Tonecontrol Board.* Replace the defective part(s).19) TAPE lN inoperative.1) Poor contact in TAPE lN input jack.x Repair or replace it.2) Fault

50、y TAPE MONITOR switch.x Repair or replace the faulty switch.20) Overload protector circuit does notwork.1) Defective SCR D 315.x Replace the defective SCR.2) Defective resistor R 331 or 333.x Replace the defective resistor(s).3) Defective capacitor C 319.x Replace the defective capacitor.4) Defectiv