PIONEER - SPEC-4 - Stereo Power Amplifier - Service Manual 电路图 维修手册.pdf

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1、STEREO POWER AMPLIFIER flD PIONEER SERVICE MANUAL RadioFans.CN 收音机爱 好者资料库 SPEC-4 MODEL SPEC-4 COMES IN TWO VERSIONS DISTINGUISHED AS FOLLOWS: Type Voltage Remarks KU 120V only U. S. A. model S 110V, 120V, 220V and 240V (Switchablel General export model This service manual is applicable to KU(p2p40)

2、and S(p41p48) types. For servicing of S type please refer to KU type with the exception of descriptions in the Additional Service Manual (P41-p48). CONTENTS 1. SPECIFICATIONS 2 2. FRONT PANEL FACILITIES 3 3. CONNECTION DIAGRAM 4 4. BLOCK DIAGRAM 5 5. CIRCUIT DESCRIPTION 5.1 Power Amplifier 6 5.2 Met

3、er Amplifier 6 5.3 Protection Circuit 7 5.4 Power Supply Circuit 9 5.5 Others 9 6. DISASSEMBLY 10 7. PARTS LOCATION 11 8. ADJUSTMENTS 8.1 Power Amplifier 14 8.2 Meter Amplifier 15 9. EXPLODED VIEWS 9.1 External Part 17 9.2 Internal Part 19 10. SCHEMATIC DIAGRAMS, P.C. BOARD PATTERNS AND PARTS LIST 1

4、0.1 Schematic Diagram and Miscellaneous Parts 22 10.2 Meter Amplifier Assembly (AWM-113 25 10.3 Power Amplifier Assembly (AWH-065) 31 10.4 Fuse Assembly (AWR-143) 36 10.5 Power Supply Assembly (AWR-139) 38 10.6 Power Supply Assembly (AWR-140) 39 1 11. PACKING 40 Additional Service Manual 1. CONTRAST

5、 OF MISCELLANEOUS PARTS 42 2. EXPLODED VIEW 43 3. SCHEMATIC DIAGRAMS, P.C. BOARD PATTERN AND PARTS LIST 3.1 . Schematic Diagram and Miscellaneous Parts 45 3.2 Fuse Assembly (AWR-144) 48 1. SPECIFICATIONS Semiconductors ICs 2 Transistors 61 Diodes 62 Power Amplifier Circuitry Current mirror loaded di

6、fferential Amplifier, 3-stage darlington parallel push-pull, direct-coupled OCL. Continuous Power Output from 20 Hertz to 20,000 Hertz (Both channels d r i v e n ) . . . 180 watts per channel (4 ohms) 150 watts per channel (8 ohms) Total Harmonic Distortion (20 Hertz to 20,000 Hertz, 8 ohms) Continu

7、ous rated power output 0.01 % 75 watts per channel power output 0.01% 1 watt per channel power output 0.01% Intermodulation Distortion (50 Hertz: 7,000 Hertz=4:l, 8 ohms) Continuous rated power output 0.01% 75 watts per channel power output 0.005% 1 watt per channel power output 0.005% Frequency Res

8、ponse . . . . 5 Hertz to 100,000 Hertz ? dB Input (Sensitivity/Impedance) 1V/50kohms Output Speaker 4 ohms to 16 ohms Damping Factor (20 Hertz to 20,000 Hertz, 8 ohms) 100 Hum and Noise (IHF, short-circuited, A network) 115dB Miscellaneous Power Requirements AC 120V 60 Hertz Power Consumption 760 wa

9、tts (UL) Dimensions 480(W) x 187(H) x 445(D) mm 18-7/8x7-3/8x17-7/16 in Weight: Without Package 24.5kg; 531b 14oz Furnished Parts Connection Cord with Pin Plugs 1 Operating Instructions 1 NOTE: Downloaded from www.hifienginc.coin Specifications and the design subject to possible modification without

10、 notice due to improvements. 8PEC-4 2, FRONT PANEL FACILITIES POWER SWITCH Set to ON position to energize SPEC-4. After setting to ON, there is a brief delay before sound is obtained. This is due to the operation of the muting circuit which prevents noise when the POWER is switched. This func tion d

11、oes not indicate difficulty and normal operating condition is attained in a several seconds. -PEAK LEVEL METERS When speaker systems of 8ohm nominal impedance are connected, these provide direct readout of the peak out put power in Watts. NOTE: Speaker system impedance varies according to frequency.

12、 To obtain a precise measurement of the output power, remove speaker connections and connect Bohm dummy loads across the SPEAKER terminals. METER ZERO POINT ADJUSTMENT INPUT LEVEL CONTROLS (LEFT the time constant of the low range of the NFB circuit has been eliminated, and amplification is pefrormed

13、 up to the DC stage. This improves the low range phase characteristics and tonal quality. Moreover, the low range frequency response is determined by the time constant of the input coupling section. The first stage is a PNP dual transistor differential amplifier with a current mirror circuit, which

14、enables stable operation and provides high gain from the DC to the ultrahigh frequency range. The second stage (predrivex stage) is a Class A amplifier. High voltage gain is obtained by inserting a constant current circuit for the load (voltage gain is necessary at this stage because the voltage gai

15、n of the power stage is zero). The power stage is a 3-stage Darlington connection and the final stage is a parallel SEPP. A power limiter circuit protects the power stage. Di, D 2 , D3 and D4, Ds, D6 are drive voltage limiters which prevent overdriving of the power stage. D3, De shift the DC level o

16、f the signal and Dt, D2, D4, Ds conduct the overdrive voltage to prevent the power stage being overdriven. NOTE: Since the power supply voltage of the power stage is lower than that of the drive stage at high outputs, Dit D2 and D4,D$ conduct the overdrive voltage. The power limiter is a current-det

17、ection type. This limiter detects the current forced thru the power transistor by the voltage generated by the emitter resistance of the power transistors. When the output has exceeded 180W at a load of 4 ohms or less, Q 1 3 Q 1 6 operate to limit the drive voltage. This prevents the output from inc

18、reasing even if an input greater than this is applied. 5.2 METER AMPLIFIER A peak output meter is provided which permits direct reading of an 8 ohms load output from 0.01W to 300W. The meter amplifier consists of the logarithmic compression circuit, absolute value detection circuit, peak hold circui

19、t, and meter drive circuit shown in Fig. 2. Constant current load circuit -Positive drive voltage limiter Input o Fig. 1 Power amplifier circuit 6 Current mirror circuit Negative power iimiter Negative drive voltage Iimiter Output To overload detector -Positive power Iimiter The input signal is divi

20、ded by Ri, R2 and sent to the logarithmic compression -circuit. The loga rithmic compression circuit is an audio IC (TA7136P2) and utilizes the rise characteristic of diodes Di, D2 in the NFB loop to reduce the dynamic range of the signal. This creates an input/output characteristic which attenuates

21、 low level inputs very little and high level inputs sub stantially. The characteristic is compensated by inserting R4 in parallel with Di, D2 and the circuit is temperature compensated with a thermistor so that the meter scale is almost logarithmically graduated from 0.01W to 300W. The compressed si

22、gnal is applied to the absolute value detector. This circuit produces a reverse phase signal by means of Q2 and extracts and combines the positive half cycle by means of Q3 and Qa. This signal charges Ci up to the peak value and drives the meter by means of Qs, Qe. The charge across Ci is discharged

23、 at the time constant of Ci and Rs to determine the fall time of the peak indication of the meter. The frequency response of the peak meter is given in Fig. 3. Logarithmic compression circuit Absolute value detector SPEC-4 5.3 PROTECTION CIRCUIT This circuit protects the power transistors in case of

24、 overload, the speakers in case of power amplifier malfunction, and also performs a muting function when the power supply is turned ON or OFF. The protection circuit is composed of three sections (Fig. 4). 1. Relay Driver Circuit (Fig. 5) The relay which connects the output circuits is driven by thi

25、s circuit. It also performs a muting function to prevent unpleasant noise during ON- OFF operation of the power supply as well as opening the output circuit on command from the detettor circuits. Power amolifier Overload Detector Center point Potential Detector Relay Drive Fig. 4 Block diagram of pr

26、otection circuit Q) Peak meter Fig. 2 Meter amplifier circuit V Relay Input Peak hold circuit Meter drive circuit Fig. 3 Frequency response of the peak meter Muting Operation When the power supply is turned ON, Q M base is reverse biased through D2 and R22 turning Q n OFF Qi2 base potential rises as

27、 Ci charges through Ri & R2, and Q12 & Q 1 3 turn ON several seconds later. The collector current of Q13 then flows through the relay coil, operating the relay to turn on the power amplifier output circuit. The reverse bias of Qn base from D2 & R22 disappears when the power supply is set from ON to

28、OFF. Q n remains ON however, due to the residual power supply voltage. Ci very rapidly discharges, Q12 base potential drops and Q12 & Q 1 3 turn OFF. The relay releases and the power amplifier output circuit turns OFF. NOTE: Ql 0 is normally OFF due to base bias and does not participate in the mutin

29、g operation. Fig. 5 Relay drive circuit Operation by Detector Circuit Command Command from the detector circuits pass through one of D3, D4 or D s and are applied in the form of a current flow. Qi 0 is normally reverse biased through Rs, but when a large current flows through on of these diodes, Qi

30、0 base potential declines according to the voltage drop at Rs- Q 1 0 then turns ON, Qn base potential rises and Qn turns ON. Ci rapidly discharges and Q 1 2 base potential drops, turning Q J 2 & Q 1 3 OFF. The relay releases and the power amplifier output circuit becomes cut off. 2. Overload Detecto

31、r Circuit Shorting of the power amplifier load or a load impedance below the specified value causes a command to be sent to the relay drive circuit. This is illustrated in Fig. 6. With the output stage in class B operation, when Qa is operating in the positive half cycle, Qb becomes cut off and the

32、signal current flows as indicated by the solid arrows in Fig. 6. Point D potential at this time is the point A potential divided by R49 and R 5. Also, point C potential is the point A potential divided by Rd and RL (load). Point D is connected to Q12 base and point C to Q i 2 emitter through R4 8 an

33、d Re2. When RL is extremely small, the point C potential becomes considerably lower than point D. This potential difference forward biases Q ! 2. Q12 turns ON and current flows in D3. Qb operates in the negative half cycle and Qa becomes cut off. The signal flows is indicated by the broken line arro

34、ws in the center of Fig. 6. Q12 is biased by the potential difference between point C and point E. If RL is extremely small, the point C potential becomes considerably higher than that of point E. Qj 2 turns ON and current flows in D3. If large current flows in Qa and Qb, Q12 becomes ON due to the R

35、ei and Re2 voltage drops, and current flows in D3. C24 prevents faulty operation due to external noise. Fig. 6 Overload detector 3. Center Point Potential Detector Circuit If a DC potential is produced at the junction point of the power amplifier, a command is sent to the relay drive circuit. Fig. 7

36、 shows this operating principle. Q8 and Q9 compose a differential amplifier. When the same input is applied to both input terminals (Q8 and Q 9 bases), no output is present. However, if there is a difference between the terminal inputs, the difference is amplified and becomes the output between the

37、two collectors. During normal opera tion, an AC signal only is present at the junction point. As C3, C4 reactance is sufficiently low, the same signal is applied to Q 8 and Q9 bases, resulting in an absence of output at the collector sides. When a DC potential is produced at the junction point, it b

38、ecomes the input of Q 9 only. If the voltage is negative, Q 9 collector current declines. s SPEC-4 and at Qs the collector current increases and the potential drops, causing current to flow through D5. If the DC voltage is positive, Q 9 collector current increases and the potential drops, while at Q

39、8 the collector current decreases and the potential rises. Current therefore flows through D. Fig. 7 Center point potential detector Fig. 8 5,5 OTHERS The electrolytic capacitor ground connection is a 20mm x 2mm copper plate. A cord (inner conductor 2.030, 0.2540 x 41 stands) having a DC resistance

40、of about 1/4 that of com mon elecrric wire is used in the power supply, output, and ground circuits. The input attenuator covers the 0 to -20dB range in 22 steps. The final position is 5.3 POWER SUPPLY CIRCUIT Two power transformers are used. The left channel and right channel power stage power supp

41、lies are independent. Power is supplied to each channel by a bridge rectifier and two 22,000/iF high capacity capacitors. The power supply before the predriver and for the main amplifier, protection circuit, etc. is supplied to each part thru a bridge rectifier and minus and plus voltage regulators

42、by connecting the windings (different from that of the power stage) of the two power transformers in series. Surge Current Counter measures When the power of an amplifier having two high capacity power supplies such as this unit is turned ON, an extremely large rush current flows. The time the left

43、and right power transformers are powered is staggered somewhat in this amplifier to reduce this rush current to a minimum. When the power switch is turned ON, T2 (right channel power transformer) is immediately power ed, but since the relay contacts are open, Ti (left channel power transformer) is n

44、ot powered. When current flows in the coil of the relay, the relay contacts are closed and Ti is powered. The rush current is reduced by one half during this 79msec delay. 9 6. DISASSEMBLY Top cover Remove the 12 screws(A) to detach the top cover. Front panel Loosen the set screws of the 2 LEVEL kno

45、bs with an hexagonal wrench and remove all the knobs. Remove the 8 screws(B) and 2 nuts(D) to detach the front panel. Bottom plate Remove the 17 screws(C) at the bottom plate and lift off the bottom plate. Fig. 9 1 D SPEC-4 7. PARTS LOCATION Front Panel View Handle ANK-084 Knob (RIGHT LEVEL) AAB-153

46、 Knob (LEFT LEVEL) AAB-153 Peak meter (RIGHT) AAW-068 Lever knob assembly (POWER) AAD-109 Handle ANK-084 Peak meter (LEFT) AAW-068 Front panel assembly AN B- 508 Front View with Panel Removed Variable resistor 100k2 LEFT (LEVEL) ACV-021 Lamp (bar type) 8V ( 300mA AEL-077 Lamp (bar type) 8V ( 300mA A

47、EL-077 Lever switch (POWER) ASK-080 Peak meter (LEFT) AAW-068 Peak meter (RIGHT) AAW-068 _ Variable resistor 100k2( RIGHT LEVEL) ACV-021 1 1 Power amplifier assembly AWH-065 Power amplifier assembly AWH-065 Heat sink Heat sink Electrolytic capacitor 22,000/iF/80V ACH-056 Electrolytic capacitor 22,00

48、0/iF/80V ACH-056 Power transformer (LEFT) ATT-416 Power transformer (RIGHT) ATT-417 Top View 1 2 SPEC-4 Bottom View 5P housing AKX-017 6P housing AKX-018 Fuse 6A AEK-109 Fuse 1.5A AEK-104 Fuse 1 A AEK-106 Power supply assembly AWR-140 Meter amplifier assembly AWM-113 5P housing A K X - 0 1 7 6P hous

49、ing A K X - 0 1 8 Ceramic capacitor 0 . 0 1 a i F / 2 5 0 V ACG-001 Fuse assembly AWR-143 Power supply assembly AWR-139 Ceramic capacitor 0 . 0 1 m F / 2 5 0 V ACG-001 Rear Panel View 2 P terminal (INPUT) AKB-034 Terminal (GND) AKE-019 Spacer AEC-379 Spacer AEC-379 AC socket (AC OUTLET) AKP-002 Terminal (OUTPUT) A K E - 0 3 7 AC power cord ADG-013 13 8. ADJUSTMENTS 8.1 POWER AMPL