ADC-SoundShaperThree-eq-sm维修电路原理图.pdf

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1、ServiceManual STEE() FE()UEN(YE()UALllEfl Audio Dynamics Corporation RadioFans.CN 收音机爱 好者资料库 -CONTENTS- PAGE ELECTRICALPERFORMANCESPECIFICATIONS3 CI RCUITDESCRiPTION,4-9 SWITCHFUNCTIONS0-12 DISASSEMBLYINSTRUCTIONS2 BLOCKDIAGRAM. ADJUSTMENTPROCEDURES- CALIBRATORSCHEMATIC. . . . .- TROUBLESHOOTING- SY

2、MPTOM CAUSE/REMEDYi7- : AMP P. C. B. (TOP (2) When 0801is barely conductinga small amountof feedback exists. Therefore,the gain of the amplifieris very high. Lessthan one millivolt willcause the outputto change by a volt or more. Operationis as follows:Anegative input causes a positive-goingchange i

3、n the amplifieroutput.Since the gain is high until0801 conducts fully,the amplifieroutputjumps to 0.2 Voltslong before the inputreaches a millivolt(in a very short time). Atthispoint0801is fullyconducting,has a low impedance compared to RF(n), and exhibitsa 0.2 V dropacross it. The rectifieroutputis

4、 now -85mV DC. Since the feedback loop (RF)has been completedby 0801any furtherdecrease in input voltage is amplifiedby the ratio of RR.(n) which is approximatelyequal to 5 for this circuit.In A positiveinputcauses the outputto decrease in a manner similarto just described except the feedbackis thro

5、ugh0803and RF (p). The amplifieroutputis blockedfromappearing at the rectifieroutputby 0801(0801is reverse biased withrespect to the followingstages which are returned to the 0 V DC line). In this manner, appearing at 0801 cathode are negative half-wave pulses whose amplitudeis directly proportional

6、to the input signal level. The followingrefers to the complete schematic: The negative pulses at 0801 cathode are filteredinto an average DC voltage by R809 and C807, and this voltage servesas input to the LED meter comparator. R803 and 0803serve to maintainpositive feedback aroundRC4709 during the

7、positive half-wave excursions of the input signal. As the amplifiersoutputis positive during this time, 0803 is forward biased (0201is off)and the feedback path now consists of R803 and 0803. The amplifieris thus kept out of saturationand free from oscillationsthroughoutthe full input cycle. Bias ci

8、rcuituses splitpower supplywhichprovides +15.4 V DC at Pin No. 14 and -15V DC at Pin NO.7on IC801. r-_R_F-/V(Ny-e_g_.)- - - - .- - 0RECT IFIE R OUTPUT 0801 RF(Pos.)0803 (AMP OUTPUT) BASIC OP. AMP.RECTIFIER-AMPLIFIERCIRCUIT Figure C COMPARATORCIRCUITFOR LED LEVEL METER DESCRIPTION Comparatorcircuitop

9、eration Comparatorcircuitconsts of 13 ICs MJM-4588DM. Comparatoroperates by comparingthe (-)input level to (+) input level, in which outputvoltage is changed from minus to plus Voltage. Thus DC currents flows to each LED. - 6 - Withno signal, (-)inputlevel No.2(L) or No.6(R)1is kept to 0 V DC. (+)in

10、putlevelPinNO.3(L)or PinNo.5(R)lofIC814is keptto minusDC voltage(about -45mV)by half-waverectifiersthroughVR801(L)VR802(R)land VR805(L)VR806mn Thus,theoutputvoltageofIC814PinNo.1(L)or No.7(R)1is keptwithminusDC voltage. When minusDC voltageis appliedto (-)input,and causes the (-)inputvoltageto be gr

11、eater (or equal) to the (+) inputvoltage,the outputappears as plus DC voltage.(V3:s.V2) ThusLEDD925(L)and D926(R) are lit at -12dB points.ButD901throughD924are notlit because the inputvoltageis too low. Each LEDconductswitha (-)inputlevel whichis determinedby VR801(L), VR802(R) (IC802), R813 (L),R81

12、4 (R) (IC803),R817 (L).R818 (R) (IC804),R821 (L),R822(R)(IC805),R825(L), R826(R)(IC806),R829 (L),R830 (R) (IC807),R833 (L),R834 (R) (IC808),VR803(L), VR804 (R)(IC809),R839(L),R840(R)(IC810),R843(L),R844(R)(IC811),R847(L),R848(R) (IC812),R851 (L),R852 (R) (IC813),R855 (L),R856(R) (IC814). Withan incr

13、ease in minusDC voltage,providedto the (-)input,each LEDis lit in sequence from D923,D924 to D901,D902. CIRCUITDESCRIPTION FREQUENCY EQUALIZATION Theinputsignal is fed intoTR101base. TR101,an emitterfollower,providesthe highinputim- pedancerequiredby thesignalsource.Thelow outputimpedanceof TR101is

14、requiredto drive a voltagedividerformedby R111 and the sectionsof the frequencycontrolpotsbetweenthe cut end ofeach controlandits wiper.Thewiperof each controleffectivelyqroundsonlythose free quenciesresonatedby the series traps(coil,capacitorand resistorfromwiperto common).Thus, the voltagedivision

15、whichoccurs can be differentfor each frequencyand depends on the frequency controlsettings. TR103,TR105and TR107are connectedso thatthe voltageat TR105base alwaysfollowsthe voltageat T R103 base. For example:An increase in voltageat TR 103 base causes the conductionof TR 103 and TR 107 to increase,

16、and feedbackbase driveof TR 105 to increase, untilthe voltageat TR105base is equaltothatat TR103base. Conductioncannotincrease beyondthispointsince the emittervoltagesuppliedby TR105thentends to make TR103conductless. Conversely,a de- crease in voltageat T R 103 base causes a correspondingchange at

17、T R105 base. Theoutputvoltageis takenfromTR107collectorand is also fed back to TR105base throughthe voltagedividerformedbyR115 and the sectionsof the frequencycontrolpots betweenthe boost end of each controland its wiper. Foreach frequency,movingthecontrolpotoffcentertowardsboostcauses an increasein

18、 the amplitudeof the signal presentedto TR103base and a decrease in the negative feedbackto TR105 base. The gain is thusincreased.Since the signal amplitudesat the bases of T R103 and T R105 are alwaysequal,the outputsignal dividedby the feedbackattenuation(R 115 and boostsections)is approximatelyeq

19、ualtotheinputsignalamplitudedividedby theinputattenuation(R 111 and CUTsections).By followinga similarline of thought,it willbe seen that when the controlsare centeredthe gain is unity;and when the controlsare towardscut, the gain is less than one. Theresistorsin series withthe series resonantcircu

20、its are used to increase the bandwidthor lower theQ,ofeach circuitso thattheeffectof controlsof adjacentfrequenciesoverlap,thuspro- vidinga smoothoverallresponse.Theresistorsare ofdifferentvaluesso thatthetotalseries resistanceof each circuit(coiland resistor)is approximatelythe same. The ratioof th

21、e totalseries resistance of the resonantcircuitto the base resistorof TR 103 and TR 105 determinesthe maximum boost or cut obtainable. -7 - SIGNAL GAIN CONTROL CIRCUIT Signal Gain Controlcircuitconsists of T R109, 111, 113 and 115 (L ch) and TR 110, 112, 114 and 116(Rch). This circuitconfigurationis

22、 identicalto theFrequencyEqualizationcircuit.For operating,see FrequencyEqualizationdescriptionsection. The input signal is fed into TR 109 base. TR111,TR113and TRl15are connectedso thatthe voltage at TR105base always followsthe voltage at T R111 base. Totalgain can vary fromnegative feedback value

23、which consists of R135, VR101and R143 (L ch) R136,VR102and R144 (R ch). When basevoltage of T R111 is equal to base voltage of TR 113, the gain is unity. COMPARATORCIRCUITFOR SIGNALGAIN CONTROLINDICATOR(LED Comparatorcircuitconsists of three ICs NJM 4558DM. ComparatoroperatesbycomparingtheINPUTsigna

24、ltooutputofTR 115. These signals are suppliedtoPin 6 and Pin 2 ofIC201(Lch)or IC202(Rch) . Bothinputlevels are doubledto outputterminals(Pin 6 to Pin 7 and Pin 2 to Pin 1). Outputof Pin 7 is positive, half-wave rectifiedby D203 and filteredinto an average plus DC voltage by C207 and R221, and this v

25、oltage is applied to(+)input at pin 3 of IC203. In the same manner, the outputof pin 1 is positive,half-wave rectifiedby D201 and filteredinto an average plus DC voltage by C205 and R233, and this voltage is applied to the (-)input at pin 2 of IC203. Thus, the differencelevel between Pin 2 to Pin 3

26、appears at Pin 1 of IC203. This voltage at Pin 1 serves as input to the Signal Gain ControlindicatorLED. For example,when theinputlevel at Pin 2 is small comparedwithPin 3, the outputat Pin 1 appears as positive voltage (approx.13.6 V DC). Thus, LED D1003 willlight but D1002 will not. When the input

27、level at Pin 2 is greater comparedwithPin 3, the outputat Pin 1 appears as a negative voltage (approx. -12.3V DC). Thus, LED D1002 willlight but D1003 will not. When the inputlevel at Pin 2 is equal to Pin 3 input level, the outputwill appear as zero, and thus both LEDs D1002 and D1003 willlight. In

28、 this case, the gain is unity.(Figure D) OSCILLOSCOPE SS-3 ,- - -f-o c:= oMH0illiMMIIlII1 o0o-+-:BBBBBBBBBBBB BBBB88BBB888c:;- fPo INPUTOUTPUT AUDIOOSC.FREQUENCYAC V.TV.M. (20. 20KHz)EQUALIZER I- I- :;):;) Q.Q. Z02090210 0100201003 Figure D -8- IIoff. POPPINGNOISEPROTECTIVECIRCUIT This circuit elimi

29、nates the popping noise in the speakers when the power switch isturned onor This circuit consists of TR201, TR202, TR203 and a Reed Relay. When power is switched on,-0.5VDC is provided to the baseof TR201 through R238. TR201 will turn off. Afterabout 6 seconds, TR202, TR203 will turn on. Thus the Re

30、ed Relay will restore connections to the OUTPUT Terminals. When the power switch is off,1.7 VDC is provided to the baseof TR201 through R237. TR201 willturnon, TR202and TR203willturnoff. And thus the Reed Relay will disconnect the OUTPUT. LED METEROPERATINGCHART AC INPUT AT VR301RECTIFIEDDC VLED MET

31、ERLED METERVOLTAGEACROSS (Max. CW)AT C807 (-)INDICATIONCURRENTEACH LED mV RMS1 KHz(mA)DC VOLTS SeeNOTE1.SeeNOTE 2.SeeNOTE 3. 12 mV-53mV DC-12dB2.63 mA1.84 V DC 15 mV-76mV DC-10dB2.63 mA1.84 V DC 19 mV-102mV DC-8dB2.63 mA1.84 V DC 24 mV-132mV DC-6 dB2.63 mA1.84 V DC 29 mV-166mV DC-4dB2.63 mA1.84 V DC

32、 35mV-205mV DC-2dB2.63 mA1.84 V DC 46 mV-278mV DCOdB2.63 mA1.84 V DC 65 mV-395mV DC+2 dB2.63 mA1.84 V DC 74 mV-453mV DC+4 dB2.63 mA1.84 V DC 100 mV-618mV DC+6 dB2.63 mA1.84 V DC 120 mV-740mV DC+8dB2.63 mA1.84 V DC 150 mV-940mV DC+10 dB2.63 mA1.84 V DC 190 mV-1.18V DC+12 dB2.63 mA1.84 V DC -9 - Recti

33、fied DC V and LED Meter data for actual levels used for LED Meter indication.(LED ON condition) NOTE: 1.AC signal applied to INPUT jacks of Equalizer. BY-PASS/EO switch to EO, METER switch to IN, LINE/REC to REC and MONITOR to OUT. 2.Rectified DC voltages measuredfrom C807 (-). 3.Indicatedvoltages a

34、cross each LEDindicatorare obtained withLED Meters calibratedas specified in the CALIBRATORPROCEDURE section of this manual. 4.All DC voltages are within10%, measured with ACVTVM and DC Voltmeter(over 10 Kn/V). l SWITCHFUNCTIONS (Applicable to LEFT or RIGHT CHANNEL) LlNE-REC and MONITORSWITCHES IN L

35、lNE-REC 2120 BY-PASS 89 BY-PASS 1211 MaN 1617 INPUT p IN lOUT - - - -.-41 - - - - - - - -_/ EQUALIZER/SIGNALGAIN CONTROL CIRCUITL- AAA_J TR101,103,10S,107,109,111,113,11Sand CONTROLS MaN Figure 1 LINE-REC SWITCH IN LlNE-RECBY-PASS 21208-9 BY-PASS 1211 2423 OUTPUT INPUT MaN INOUT EQUALIZATION/SIGNAL

36、GAIN CONTROL CIRCUIT Figure 2 LINE-REC, MON ITO R and BY-PASS SWITCH ES OUT MaN 2423 BY-PASS 89 BY-PASS 1211 INPUT r7i OUTPUT LlNE-REC INOUT EQUALIZATION/SIGNAL GAIN CONTROL CIRCUIT 2 LlNE-REC TAPE OUT Figure 3 MONITOR SWITCH IN LlNE-REC 2 MaN 2223 LlNE-REC 1514 PUT., OUTPUT 11 BY- PASS 12 INOUT EQU

37、ALIZATION/SIGNAL GAIN CONTROL CIRCUIT Figure 4 -10- Figure 8 WHEN BY-PASS SWITCH IS IN,LED METERS INDICATEAT 0 dB POINTS ONLY, REGARD- LESS OF OUTPUT SIGNAL. NOTE: RIGHTCHANNELLED METERINDICATESOUTPUTOF SOUNDLEVELMETER WHEN CONNECTED TO SLM JACK. (METER SWITCH IN EITHER POSITION) - 11 - BY-PASS SWIT

38、CH IN MON 2423 BY-PASS 87 BY-PASS 1011 MON 1817 INPUT L1NEREC INOUT EQUALIZATION/SIGNAL GAIN CONTROL CIRCUIT Figure 5 BY-PASS and MONITORSWITCHES INMON MONBY-PASSBY-PASSL1NE-REC 22238710111514 INPUTOUTPUT LINE-REC INOUT EQUALIZATION/SIGNAL GAIN CONTROL CIRCUIT Figure 6 METER SWITCH IN BY-PASS/EO SWI

39、TCH TO BY-PASS OUTPUT 27 26BY- PASS - B line (- 5.6 V) Figure 7 BY-29 PASS30 R145 (R146) Comparator LED METER INDICATESSIGNALAT OUTPUT JACK WHEN METER SWITCH IS IN. METER: LED METER METER SWITCH IN BY-PASS/EO SWITCH TO EO OUTPUT HALF-WAVE RECTIFIER AND COMPARATOR CIRCUIT METER SWITCH IN BY-PASS/EO S

40、WITCH TO EO INPUT BY-PASS r-, II -+, - - !,- - - - - i I, , , , ,I J SIGNALGAINCONTROL COMPARATOR EQUALIZER L.-.-+-!aSIGNALGAIN CONTROLCIRCUIT 01003 (01005) 01002 (01004) SIGNALGAIN LED Figure 9 WHEN BY-PASS SWITCH IS INAND METER SWITCH IS OUT,SIGNAL GAIN CONTROL LED DOES NOT INDICATEREGARDLESS OF I

41、NPUT SIGNAL. DISASSEMBLYINSTRUCTIONS 1) To remove chassisfrom metal cabinet a)Remove four screws- two from each side of cabinet asshown in Figure A. b)Remove five screwsthat fasten the rear panel to the metal cabinet. (SeeFigure B.) 2)Removal of Front Panel a)Remove chassisfrom metal cabinet asdescr

42、ibed in 1). b)Remove the four screwsfrom the top (Figure C) and four screwsfrom the bottom (Figure D) of the Front Panel. c)Remove knobs and pull panel off. NOTE: If required, remove one screw (painted red) from the top of the Front Panel as shown in Figure E. Figure A Figure C Figure E Figure B Fig

43、ure D -12- LCHANNELJ rr:QUE-NCY-E-aAiIZATIONAMP-mm-:-:-u-SIGNAL-GAIN-C-ONTROC-AMP-uuu:! IIII :EMITTERDIFFERENTIALFLAT:EMITTERDIFFERENTIALFLAT: TAPE OUTFOLLOWERAMPAMP!FOLLOWERAMPAMPf-t-, ,AMPIAMP, INPUTILn TR nTR.= _ ,:.njLu:_ :_nTR :- -n_:-:J TAP.EMON0 f sLM JACK VR301 LED METER CONTROL - - y VRIOOI

44、 SIGNAL GAIN CONTROL w I I:-METER AMPa COMPARATOR HALF-WAVE L-O-lRECTIFIER aAMP IC801 o (/, i10OUTPUT , , I I, I , , , 1-1 I I fPOPPINGNOISEI IPROTECTOR, I :L IFRQUENCYEQUALIZERGAINCONTROL-viRSUPPLY z- I I et:ZW.J o-z-c:0. I I-:380Il:z hl.Ji= t-5:Jt5tallJ.J sQ:8:Jo:f 0.(i)t-Il:a;14.o.t- g8128 ,-., f

45、SiGNACGAIN CoNTROL AMP- !- _aC,OMPARATOR COMPARATOR IC 203 IL_ _ SIGNALGAIN CONTROLLED METER I SWITCHING TR201,202 ,203 _ =_J OUT +B-8 T 01001 , , :1I._j I, :I ,:, II ,I ,I ,0702I ,-_jI FREQUENCYSELECTOR - - - - / m r- o n c - :a s: ADJUSTMENTPROCEDURES (1)SIGNALGAINCONTROLADJUSTMENT EOUIPMENTREOUIR

46、EO(See Figure10) 1. AudioOscillator 2. AC Voltmeter 3. Calibrator(dB Attenuator) 4. Oscilloscope NOTE: Maintainvoltageat 120 V AC (UL,C.S.A. and PX) (220/240V AC forEuropeanmodels). Input-INPUTJack Output- OUTPUTJack Set TAPEMONITORSwitchto OUT. Set BY-PASS/EOSwitchto EO. Set SIGNALGAINControlon Fro

47、ntPanel at center position. SIGNALGAINLEDPROCEDURE(See Figure11) (2)LEDMETERCALIBRATIONPROCEDURE ConnectLEDMetercalibrationset-up as shownin Figure10. CALIBRATOR:OFF AC VOLTMETER:0.3 V Range AUDIOOSCILLATOR:Frequency-1 KHz OUTPUT-1.5 V min.into ext. 600rlload. INT/EXTLOADSWITCH(if any) - EXT.(Calibr

48、atorbox to provide approximately600rlload to generator). FREOUENCYEQUALIZER:FrequencyControl- Flat position CenterFrequencySelectorswitch- Center position METERswitch-IN BY-PASS/EO- EO TAPEMONITOR- OUT LlNE/REC-REC Left(VR301)- Max. counterclockwise Right (VR401)- Max. clockwise Step1. Step2. Step 3

49、. AdjustAudioOscillatoroutputfor1 V at 1 KHz as read on AC Voltmeter. Set Calibratorat 0 dB. AdjustVR 101 (left)for1 Voltreading on outputAC Voltmeter and VR 102 (right)for1 Voltreading on outputAC Voltmeter. AdjustVR201(left)forbothLEDs(01002and 01003)to lightwithequalintensity and VR202(right)for bothLEDs(01004and 01005)to light withequal intensity. METERCONTROL: Ste