Scott-440A-Service-Manual 电路图 维修手册.pdf

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1、Price $6.00 Service Manual Integrated Stereo Amplifier 440A ffiSCOTL T1o lJ.-no 1-6 lc.on n RadioFans.CN 收音机爱 好者资料库 CONTENTS Specifications Block Diagram Level Diagram Circuit Description . . Adjustment . . Exploded View . . Schematic Diagram . Parts Location Diagram . . Replacement Parts List . . C

2、AUTION NOTICE 2 3 3 4 5 6 7 8 9 The following safety precautions must be followed to assure continued reliability and safety against fire and shock hazard: 1. Replacement parts used during servicing of this appliance must have identical characteristics as those offered and recommended by H. H. Scott

3、, Inc. 2. A dielectric test is to be performed on each appliance following the re-assembly and before returning the unit to the custmer. 3. The dielectric test to be performed on H. H. Scott, Inc. electric components serviced in the United States and Canada for use in these countries shall consist o

4、f not less than the following:* 1) A dielectric tester designed to supply not less than 1100 volts at 60 Hz and employing leakage current indi- cator(s), is to be used. 2) The tester is to be connected per the instructions en- closed with the instrument, or as follows: a. The tester is connected to

5、the power line receptacle and the power switch is turned on. b. Sufficient time is allowed for the tester supply to stabilize and then the output voltage is adjusted for 1080V. c. Leads of the tester, usually marked GND and HV, are connected between chassis ground and both blades of the male plug of

6、 the power cord. d. Switch tester to test and observe leakage indicator. Leakage current must not exceed 5. 0 mA. * Dielectric tests made by service personnel in countries other than USA and Canada must use test equipment and pro- cedures specified by the safety agency serving that country. SPECIFIC

7、ATIONS Minimum Continuous RMS Output Power per chan- nel both channels driven into 8 Ohms from 20 Hz - 20 kHz with no more than rated THO 55 watts Total Harmonic Distortion 78 IHF rated, at 20 Hz -20 kHz 0.05% Intermodulation Distortion at rated output, 60:7000 Hz; 4: 1 0.08% Frequency Response at 1

8、 watt output, 0.5 dB 20 Hz to 20 kHz Power Bandwidth at -3 dB 10 Hz to 30 kHz Damping Factor at I kHz, for 8 Ohm load 100 Input Sensitivity for rated output Phono: 2.5 mV Aux, Tuner: 150 mV Tapeland2: 150mV Tape 2 DIN Input: 150 mV Maximum Input Voltage Phono: 180 mV Aux, Tuner: l0V Tape 1 and 2: lO

9、V Tape 2 DIN Input: lOV Signal-to-Noise Ratio shorted input, IHF A network Phono, Ref. 10 mV: 85 dB Aux, Tuner: 90 dB Tapeland2: 90dB Tape 2 DIN Input: 90 dB Tone.Control Range Bass (100 Hz): 10 dB Mid (1 kHz): 6 dB Treble (10 kHz): 10 dB High Filter Attenuation 6 dB/oct. 8 kHz: -6 dB Loudness Conto

10、ur Volume Control set to -30 dB 100 Hz: +7 dB 10 kHz: +3.5 dB Crosstalk 1 kHz: 80 dB Channel Balance maximum Volume Control 0.5 dB RIAA Tolerance 78 RIAA rated, 20 Hz to 20 kHz 0.5 dB Channel Separation 78 IHF rated Phono 1 and 2 (1 kHz): 60 dB Aux, Tuner, Accessory Input, Tape 1 and 2, Tape 2 DIN I

11、nput (1 kHz): 70 dB Tape Recording Output Level at rated input sensitivity level Tape 1 Rec: 150 mV Tape 2 Rec: 150 mV Tape 2 DIN Output: 30 mV AC Power Requirement 117V AC 60 Hz (USA/Canada version) 100V/117V/220V /240V, switchable AC 50/60 Hz (European version) Power Consumption 160 Watts (USA/Can

12、ada), 430 Watts (Europe) Dimensions 17W, 5-1/4H, ll-3/4D 430W, 132H, 330D (mm) Net Weight 23.5 lbs. (10.6 kg) RadioFans.CN 收音机爱 好者资料库 BLOCK DIAGRAM P!IONO fUNER UX REC APE 1 PLAY REC APE2 PLAY RIGHT CHANNEL (SAME AS LEFT CHANNEL) LEVEL DIAGRAM +50 +40 +30 +20 -22,2V 0 dB (lV) -10 AUX,TUNER,TAPEPLAY

13、,- ll -20 150 mV I VOL AMP - rfR_fo.HLF:-7 -,.,_,- 1MJ1 1,BAI L _ J RELAY CIRCUIT TONE AMPLIFIER -. I POWER ./ AMPLIFIER /voLiME AMPLIFIER TONE +20 dB -CONTROL 0 dB I -30 I I PHONO EQUALIZER +35.5 dB -40 -50 PHONO I l -60 2.5 mV 21V +23 dB SPEAKERS A SPEAKERS B R AC POWER RECEPTACLE POWER METERS R T

14、OTAL=78.5 dB 3 RadioFans.CN 收音机爱 好者资料库 CIRCUIT DESCRIPTION Phono Preamplifier This is a negative feedback type RIAA equalizer. It consists of 3 low noise transistors per channel. Open loop gain of the circuit is 83 dB. Negative feedback consists of Rl, R2, Cl, and C2 is applied from the emitter of Q

15、3 to the emitter of Ql giving gain of 35.5 dB 1 kHz and correcting the response to the RIAA equalization standard (+12.9 dB 100 Hz, -13.7 dB 10 kHz). An additional rolloff below 30 Hz is pro- vided by C3. The circuit is powered by split supply of 22V, providing an overload capability of greater than

16、 180 mV at 1 kHz. R3 C3 -+-r INo-H. -22.2VO Volume Amplifier +22.2V RI R2 CI C2 The signal from the Volume control, VR2, is amplified 20 dB by the directly connected amplifier stage consisting of Ql and Q3 (refer to the Block Diagram). Gain is set by the ratio of R17 to R15. Tone Control The tone co

17、ntrol is a negative feedback type which utilizes common emitter amplifier Q5 and emitter follower Q7 as the active elements. That is, the gain of Q5 is controlled by the tone control circuitry. R3 VRI R4 VR3 Mid Tone Control: At 1 kHz, other two tone controls have little effect on the gain, as C4 im

18、pedance is high, removing VRl from thi: circuit, and C7, CS impedances are low, effec- tively short circuiting VR3. Thus at midrange frequencies near 1 kHz, the gain is mainly determined by the position of VR2. Bass Tone Control: As the frequency decreases below 1 kHz, the impedance of C7, CS increa

19、ses proportionately. At very low frequencies, C4 and CS are effectively open, removing VRl and VR2 from the circuit. Thus at low frequencies, the 4 gain is mainly determined by the position of the Bass tone control VR3. Rotating VR3 toward Rl0 will boost the low frequencies, while turning it towards

20、 Rll will cut the bass. Treble Tone Control: At high frequencies, as at 10 kHz, VR2 and VR3 are effectively short circuited. At these frequencies, however, C4 impedance decreases, so that VRl becomes the main control of the circuit gain. Rotating VRl towards R3 will boost the treble, while turning i

21、t towards R4 cuts the treble response. Power Amplifier This circuit is an OCL, fully complementry amplifier. The input stage consists of a differential amplifier (Q4 +5) and a voltage amplifier (Q7). The voltage amplifier provides voltage swing to nearly full plus and minus supply. Current gain is t

22、hen provided by the fully complementary Darlington pairs of Q12 and Q13 for the positive swing, Q14 and Q15 for the negative swing. The output stage bias is set by the quadruple diode Dl and RVl. The output stage is protected from short circuit and overload by transistors QB thru Qll, which short ou

23、t the driving signal when current through the output transistors reaches an ex- cessive level. ANOTHER CH DRIVER QI2 QI3 +B OUT IN -B Relay Protection Circuit The circuit protects the speakers from the possibility of DC potential at the amplifier outputs, as well as eliminating transients during tur

24、n on or turn off. Tum On/Off: When the unit is first switched on, Q2 quickly turns on, holding Q3 off. Charging time of Cl through R6, Q2 turns off, thus turning on Q3 and activating the relay which connects the audio output to the speakers. At turn off, Q4 immediately turns on, which turns Q2 on an

25、d Q3 off in- stantly opening the speaker relay. Center Point Potential Detect: This circuit, composed primari- ly of Ql, D1 and D2, protects the loudspeakers from DC at the amplifier output. When excessive plus or minus DC ap- pears at Rl or R2, Ql turns on, which activates Q2 and opens the speaker

26、relay. At the same time, LDl, the front panel pro- tection indicator, is activated. ADJUSTMENT Equipment Required Audio Signal Generator. DC Voltmeter. Speaker load resistors, 8 ohm, 100 watt (noninductive). Digital voltmeter or DC milliammeter. The following adjustments are the same for both the le

27、ft and the right channels. Bias Adjustment 1) Connect 8 ohm resistors to the Speaker A terminals, and set the Speaker Mode switch to A position. 2) Turn the Volume control fully counterclockwise. 3) Turn RVl fully counterclockwise. 4) Depending on available equipment, use A or B: A. Set digital volt

28、meter to most sensitive range. Connect probes across R3 7 and R39 (Voltmeter bias test points, left channel). Turn unit on. Let it idle for at least one minute. Adjust RVl for 40 mV across the resistors. B. With unit off, remove jumper between PC board termi- nals E and E, and connect ammeter, set t

29、o 100 mA range. Adjustment Locations Volt Meter Bias Test Point (Right Ch.) Bias Adjust (Right Ch.) Bias Adjust (Left Ch.) Volt Meter Bias Test Point (Left Ch.) Power Supply (Refer to Block Diagram) The main power supply (48V) consists of a full wave bridge rectifier and two 8,200 F capacitors. The

30、B+ and B-regu- lators (Q9 and QlO) supply 22V for the low level circuitry. Turn unit on and let it idle for at least one minute. Adjust RVl for 40 mA. 5) Perform the same procedure for the right channel, except measure voltage across R38 and R40 (Voltmeter bias test points, right channel) or replace

31、 jumper from D to D with ammeter. Adjustment is made with RV2. 6) Leave the amplifier on for about 30 minutes, then recheck measurement. A tolerance of 25% is acceptable. Readjust if necessary. Power Meter Calibration 1) Connect the audio signal generator to the amplifier and apply 1 kHz signal to A

32、ux input, left channel. 2) Connect voltmeter across the left channel load resistor. 3) Turn power on. 4) Adjust the signal generator output so as to obtain 2.83 volts on the voltmeter. 5) Check that the left channel meter indicates 1 watt. If not, adjust RV3. 6) Perform above steps on the right chan

33、nel, adjusting RV4 if necessary. Meter Adjustment (Right Ch.) (Left Ch.) 5 UJ 5 0 UJ 0 9 a. X w : ., . I f, - ., q) -0 i -, ., ,1, - -,t I . = ( lfaf(t ., . . - . .,;, -: . 6 SCHEMATIC DIAGRAM 1 I TUNER TAPE I REC I R41 2.2K R43 390K R46 IOOK R44 3901( AUX R TUNER R JI PH ONO AUX TUNER J2 TAPE I IRE

34、C .PLAr) J3 TAPE 2 l REC , PLAY J J4 TAPE 2tOIN SOKET) PHONO I I ,s, I I R9 130 7 R35 121( l/2W OOBBtNG S2 01 RD22 02 R022 QI 2 Q3,4,5,6 2SA97o (GR,BL) 2SC2240 (GR.SL) 4.3 -c:;t- STEREClNO BALANCE S3 VR I R36 R33 1/2W o ,w R38 I K L _ l - C4 1/50 R2 l 82tJ,. 220P I SELfCTOR fr: eHo,o i u_ g :ER - L_

35、 PSPA039 COX Q9 2S0526 to,YI QIO 2S8596(0,YI LOUDNESS S4 VOLUME VR2 C3 .12 R3 6K C4 i R: 5.61( RS 22K R I 150K IOOP C35 + 1/ioo R6 22K l/Lf0/1 CkT, 1 H Is SH Ol( L o B t; r/0/JEJ) To TIIF /=OIL n-1c ; )i 01= Ee B (9 05.6 2SC2240 C GR.BU 07.8 2SCl81 CY.GR) HIGH FJL S5 II)if, ,. ,: , . m I :- _ B l ,:

36、t1) ll , -/. :W,! j ii;: /11/ I/ :;Ii ll ,I;,.:. I I , / / r.rw q, .:-s; = , , , _-=: :;16-, -, o: ,t PSTC028AOX PSPA039COX PSLD013COX 0 ,- . :; :t : =-a :ccc:e wO : m :2 PSPW033COX PSMA030COX 8 REPLACEMENT PARTS LIST Symbol No. Descrpiton Part Code PSMA030COX CS,6 Ceramic capacitor, 2p*, sov CCCB02

37、0COM C7,8 3p, sov CCCB030DOM C9, 10 Sp, sov CCCB0S0COM C39,40 l00p, sov CCCB101KOM C19-22 220p, sov CCCB221KOM C3, 4 330p, sov CCCB331KOM Cl, 2 Elyt capacitor, 2.2, sov CEAG2R2ZMN C31 22, sov CEAG220AMN C23-26, 35, 41, 42 1, 100V CEAK0l0ALX Cll, 12, 29, 30 100, 10V CEEC101ALX C13, 14 10, 16V CEEDl00

38、ALX ClS-18 Ceramic capacitor, 330p, sov CKCB331KBM C33, 34 Mylar capacitor, 0.022, sov CQMB223KEH C32 0.047, sov CQMB473KEH C27,28 Ceramic capacitor, 0.056, sov CQMC563KEH Ll, 2 2.5 H, AF out, w/R47, 48 LA3QH1323B D11, 15-18 Silicon diode, RA-lZ QDSRAlZXXD D5-10 1S1553 QDSS1553XT D1-4 1S1555 QDSS155

39、5XT ICl IC, TA7318P-2 QQM07318AT Q9, 10 Transistor, 2SA720 QTA0720XBN Ql, 2 2SA798 QTA0798XEE QS, 6 2SA912 QTA0912XAN Q19, 20 2SA968 QTA0968XBT Q25 2SA970 QTA0970XBT Q15, 16 2SA1015 QTA1015XAT Qll, 12 2SC1318 QTC1318XDN Q13, 14 2SC1815 (R, S) QTC1815XAT Q26,27 2SC1815 (GR) QTC1815XBT Q7, 8 2SC1885 Q

40、TC1885XAN Q17, 18 2SC2238 QTC2238XBT D13, 14 TR-diode, 4-gang, STV-4H QVFSTV4HXD R58 Metal-oxide-film resistor, 100*, 1/2W RGHANJ101N R25-28 150, 1/2W RGHANJ151N R15, 16 15k, 1/2W RGHANJ153N R59, 60 2.2k, l/4W RG1ANJ222N R56 3.3k, lW RG1ANJ332N R57 470, lW RG1ANJ471N * Capacitors are rated in F (micro-Farad) unless otherwise specified as p (pico-Farad). * * Resistors are rated in ohm. 9