Realistic-STA78-rec-sm 维修电路原理图.pdf
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1、ruLtsfiCSerulceSTA.78AM /FM STEREOCatalog Number :RECEIVER31-2077cusToM MANUFACTURED FoB RADIo sHACK In DMSIoN 0F TANDv conponAloNRadioFans.CN 收音机爱 好者资料库(1)(21(3)(4)(5)(6)(71(B)(e)( 10)(11)(121( 13)(141( 15)( 16)(171( 1B)( 1e)(20)(211CONTENTSELECTRICAL PERFORMANCE SPECI FICATIONSDISASSEMBLY INSTRUCT
2、IONS .PAGE3-5BLOCK DIAGRAMDIAL STRINGINGLEVEL DIAGRAMALIGNMENT INSTRUCTIONSTROUBLESHOOTI NGBRIEF DESCRIPTION OF PROTECTOR CIRCUITIC & TRANSISTOR LEAD IDENTIFICATIONSAM/FM TUNER, IF & MPX P.C.B. (TOP & BOTTOM VIEWS) .18PHONO EOUALIZER AMP P.C,B. (TOP & BOTTOM VIEWS) .19TONE CONTROL P.C. B. (TOP & BOT
3、TOM VIEWS) . . .2OMAIN AMP P.C.B. (TOP & BOTTOM VIEWS) ,.,.21swrTCH P. C. B. (TOP & BOTTOM VTEWS) .22NOISE MUTING P.C.B. (TOP & BOTTOM VIEWS) ,.23POWER SUPPLY P.C.B.(TOP & BOTTOM VIEWS) ,.,23ELECTRICAL PARTS LISTEXPLODED VIEW PARTSIC INTERNAL DIAGRAM561712161617DIAGRAM8-13-33-3536-3738-39tISCHEMATIC
4、 DIAGRAMEXPLODED VIEW-2-RadioFans.CN 收音机爱 好者资料库i1. ELECTRICAL PERFORMANCE SPECIFICATIONSAM BANDFrequency CoverageIFUsable Sensitivity for S/N 20 dB at 600 kHzat 1000 kHzat 1400 kHzS/N Ratio at 5 mV/m input 1000 kHzSelectivity at 1000 kHz a. 10 kHzinput = S/N 6 dB Sens. inputAGC Distortion at 1000 kH
5、z, 80% mod. 100 mV/m inputAGC Figure of MeritlF Rejection Ratio at 600 kHzlmage Rejection Ratio at 1400 kHzBandwidth at 6 dB downDistortion at 5 mV/m input, 30% mod.Tape out Level at 5 mV/m input (RCA)Tape out Level at 5 mV/m input (DlN)Fidelity Bandwidth at 5 mV/m input (1 kHz = 0 dB)Whistle Modula
6、tion of 2nd and 3rd harmonic, at 1 mV/m,5 mV/m and 100 mV/m inputDial Calibration at 600 kHzat 1400 kHzOverload: With a radiated signal of 1Ylm, the signal shallbreakup.FM BANDFrequency CoverageIFIHF Sensitivity at 90 MHzat 98 MHzat 106 MHzNew IHFS/N 50 dB Ouiting Sensitivity at 90, 98 and 106 MHzS/
7、N Ratio at l mV input3 dB Limiting SensitivitylF Rejection Ratio at 90 MHzlmage Rejection Ratio at 106 MHzSpurious Response and Cross ModulationCapture RatioAlternate Channel Selectivity 100 pV inputDistortion at 1 mV inputDial Calibration at 90 MHzAFC Holding Range at 1 mV inputTemperature Range fo
8、r Satisfactory operationAM SuppressionMaximum Signal Handling CapacityTape out Level at 1 mV input (RCA)Tape out Level at 1 mV input (DlN)UNITkHzkHzpV lmpV lmpY lmdBdBo/odBdBdBkHzo/omVmVHz%38kHz 0 r,25kHz 0 4.50tunable without undue distortion or32 254850 4235 2845 386 4.5-90.8 2200 200 *.2.5 dB15 1
9、5 r 2.5 dB50-2200 B0-1800NOMINAL510-165045520020020045LIMIT520-162050050050040beUNITMHzMHzpVpVpVdBfpVdBfdBpVdBdBdBdBdBo/okHzkHzCdBmVmVmVNOMINAL86.5-10910.71.91.91.910.82.814.2651.8855B801.5600.1a.250LIMIT88- 1 0B3.83.83.816.84.518.2553.57048654480.51 250t250 +. 1000-4542100750 .t. 2.5 dB15 a.2.5 dB5
10、020075015-3-Muting SensitivityF requency R esponse ( De-emphasis)75 pS (UL & C.S.A.)50 pS (Australian)25 pS (for FM Dolby)All sets must meet the requirements of the FCC, FTZ.FM STEREO BANDStereo I ndicator SensitivityStereo Separation at 1 mV inputStereo Distortion at l mV, 1 kHzPilot and Sub-carrie
11、r LeakageAUDIO SECTIONat 100 Hzat 1 kHzat 10 kHzinputlnput lmpedance PHONO MAG.AUXTAPE INOutput Power, TH D 0.5% from 20 Hz to 20 kHz,I ohms Both Channel DrivenOutput Power, THD 0.5% at 1 kHz Both Channel DrivenDistortion at 5 W from 20 Hz to 20 kHzSensitivity for Rated Power (22WPHONO MAG.AUXTAPE I
12、NFrequency Response at AUX from 20 Hz to 20 kHz input,1 W outputBass Action at 100 HzTreble Action at 10 kHzMin. Volume Hum & NoiseSignal to Noise Ratio PHONO MAG. (lnput shorted)AUX (lnput 10 Kohm terminated)TAPE lN (lnput 10 K ohm terminated)Cross Talk at 1 kHz AUX PositionLoudness contour ch. at
13、100 Hz -30 dB Vol. positionLoudness contour ch. at 10 kHz -30 dB Vol. positionChannel Balance at AUX, Vol. = Max.TAPE OUT Level PHONO MAG. (RCA)AUX, (RCA)PHONO MAG. Equalizer Response at 100 Hzat 10 kHzPHONO MAG. Over Load (THD = 0.5%)DC BalanceUNITpVdBdBdBNOMINAL5.5UNITpVdBdBdBo/odBUNITK ohmK ohmK
14、ohmNOMINAL5.53B48350.550NOMINAL50505025270.152.2160160F lata.10i.10165757555+9+4150150+ 13.1 1-13.751200LIMIT3.5-9.0*1ae_J*1 oa_J1l anLIMIT3.5-9.02833281.545LIMIT22240.32.2t3dB160f3dB160r3dB*-2a.10 L 2.5r_10 i.2.5355656545+9 i 2.5+4 r.2.5r-2150 r 3 dB150 i.3 dB*.2 dBr_2 dB90*.30WWo/omVmVmVdBdBdBmVdB
15、dBdBdBdBdBdBmVmVdBdBmVmV-4-Note:The supply voltage is 120 volts AC (for UL & C.S.A.) and 24O volts AC for Australian models,from a regulated power supply.The power source must be insulated from other equipment connected antenna or output. The roomtemperature is 25 degrees C.Nominal Specs represent t
16、he design specs; all units should be able to approximate these - some willexceed and some may drop slightly below these specs.Limit Specs represent the absolute worst condition which still might be considered acceptable; inno case should a unit perform to less than within any Limit Spec.2. DISASSEMB
17、LY INSTRUCTIONS1) To remove Chassis f rom wooden cabinet.Turn the cabinet upside down and re-move the six screws from the bottomcabinet. (Figure A)2) Removal of Front Panel.a) Remove the chassis from woodenb) Pull out the Main Chassis.c) Remove the two screws from the topd) Remove knobs and pull off
18、 panel.FigureAcabinet as described in 1).and three screws from the bottom of(F igure B1 , B2lthe Front Panel.3)To remove Rear Panel from chassis.Remove the four screws from the RearPanel. (F igure C)Figure B1Figure 82-5-aEUYUIIa.Iri-;- 1E59t!i-NIIO_.1auaEo=ooidooll93 e-d LF,E;-o?50 iij*i:33or;l -oEE
19、 i ooz!E;I=Pg66=N=E=oEE=EF3. BLOCK DIAGRAM-6-4. DIAL STRINGING DIAGRAM*START WITH CAPACITOR SET AT MINIMUM.PLATES FULLY OPEN (UNMESHED).*Pointer Position : HIGH END5. LEVEL DIAGRAMFIAUDIO FREQIJENCY. lkHz-7-6.ALIGNMENT INSTRUCTIONSAUDIO CIRCUIT ADJUSTMENT,/CHECKEOUIPMENT REOUIRED1. DC Voltmeter2. Au
20、dio Oscillator3. Oscilloscope4. AC VoltmeterNote: Maintain voltage at 12O volts AC, 60 Hz (UL, CSA)(240 volts, 50 Hz AC for Australian models).*Set SELECTOR Switch to AUX.*Set MODE Switch to STEREO.See P.C.B. illustration for alignment points/adjustments.For location of connection points and trimmer
21、 resistors, see P.C.B. view.(-25mV to+25mV)Figure 6Oscilloscoge (Shorled OutpuiCondition)(Normol Condiiion)Figure 5MAIN AMP ADJUSTMENTSTEPADJUSTMENTEOUIPMENT CONNECTIONAUDIO FBEO.LEVELADJUSTMENT1Check Balance bymeasuring DC voltageacross Output Termi-nal of L and R chan-nel.DC VoltMeterSee Figure 1N
22、o signalDC voltage shouldbe less than 25 mV2ldling current adjust-mentDC VoltMeterSee Figure 2.No signalAdjust so voltageacross Emitterresistors R633 ancR634 is 5 mV(8 ohm load).VR601VR602FigureCHECKING LIMITER CIRCUITSTEPADJUSTMENTEOUIPMENTCONNECTIONAUDIO FREOSETTINGLEVEL1Audio Osc.V.T.V.M.Oscillos
23、copeSee Figure 3.1000 HzVOLUME: Max.BASS, TREBLEBALANCE:centerAdjust input toAUX to get out-put level at justthe clipping point(4 ohm load)Figure 4.2Check the limiterci rcu i t.Audio Osc.V.T.V.M.OscilloscopeSee Figures 3,5.1000 HzSame as aboveCheck that outputdropt to a squarewave across R633(R634)
24、when out-put speaker termi-nals are shorted.See Figure 6.4ohm L.od,A-.-(yoc -+)AUDIO Osc. AUX SrA-79( rooHz)Figure 3Oscilloscope1J-8-AM RF & IF ALIGNMENTEOUIPMENT REOUIRED1. AM Signal Generator2. AC Voltmeter3. Oscilloscope4. Distortion MeterFigure 7Note: *Signal generator output should be no higher
25、 than necessary to obtain an output reading.*Maintain line voltage at 12O volts, 60 Hz AC (UL & CSA) (240 volts, 50 Hz AC for Australianmodels).Set SELECTOR Switch to AM.*See P.C.B. illustrations for alignment points/adjustments and Figure 7.osclLloscoPE DtsToRTloNAC VOLTMETER METERTAPE OUT(LorR)Fig
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