Pioneer A-60 Service Manual
  1. Manuals
  2. Brands
  3. Pioneer Manuals
  4. Amplifier
  5. A-60
  6. Service manual
Pioneer A-60 Service Manual

Pioneer A-60 Service Manual

Troubleshooting, supplement to tuning fork
Hide thumbs Also See for A-60:
Table of Contents

Advertisement

Quick Links

Download this manual
Service Guide
Troubleshooting Power Amplifiers
Supplement to Tuning Fork

Advertisement

Table of Contents
loading
Need help?

Need help?

Do you have a question about the A-60 and is the answer not in the manual?

Questions and answers

Related Manuals for Pioneer A-60

Summary of Contents for Pioneer A-60

  • Page 1 Service Guide Troubleshooting Power Amplifiers Supplement to Tuning Fork...
  • Page 2 The basic principle and troubleshooting are the same among the models of the same series such as A-5, A-6, A-7, A-8, A-9, SX-7, SX-8 and SX-9, and A-60, A-70, A-80 and A-90. We hope this guide is informative to you and helpful to your service, and ultimately, to your sales activities.

  • Page 3: Table Of Contents

    CONTENTS OF TROUBLESHOOTING POWER AMPLIFIERS I. Operation of Circuits 1. Development of Power Amplifiers a) Single-Ended Push-Pull (SEPP) Amplifier b) All-Stage Direct-Coupled S E P P Amplifier c) All-Stage Direct-Coupled S E P P D C Amplifier d) Non-Switching Amplifier (NSA) e) Non-Switching Amplifier (with a DC-servo circuit) 2.
  • Page 4 MEASURING EQUIPMENT & DEVICES TO BE PREPARED Multimeter A u d b Generator mV Meter * Oscilloscope Dummy Resistor 180 5 0 W - 1 0 0 W ) 2PCS (Clip type) (Stick type) Multimeter leads...

  • Page 5: Operation Of Circuits

    I. Operation of Circuits 1. Development of Power Amplifiers In 1960, a transistorized amplifier was developed by TEC in U . S . A . In the more t h a n twenty years since then, elec­ tronic technology has greatly been advanced and the per­ formance of amplifiers has been incomparably improv­...
  • Page 6 Fig. 3 All-Stage Direct-Coupled SEPP Amplifier Fig. 4 All-Stage Direct-Coupled SEPP DC Amplifier...
  • Page 7 Tone Control Circuit Fig. 5 Non-Switching Amplifier Fig. 6 Non-Switching Amplifier (with DC servo circuit)
  • Page 8 a) Single-Ended Push-Pull (SEPP) Amplifier Fig. 7 is the circuitry of the S E P P amplifier. The S E P P (2) Phase inversion is made by the combination of P N P - amplifier has comparatively good performance in spite N P N transistors.
  • Page 9 b) All-Stage Direct-Coupled SEPP Amplifier Fig. 8 is the circuitry of the All-Stage Direct-Coupled distortion. The gain, however, becomes nul in the D C S E P P Amplifier. To solve the above problems, All-Stage and extremely low range. The remaining problem is the Direct-Coupled S E P P Amplifier has been developed.
  • Page 10 c) All-Stage Direct-Coupled SEPP DC Amplifier Fig. 10 shows the circuitry of the All-Stage Direct-Coupl­ signal. Although this circuit amplifies the D C signal, D C ed S E P P D C Amplifier. This improved circuit superseded components are blocked by a high-pass filter ( H P F ) at the bootstrap circuit which had long been used in the amplifier's input.
  • Page 11 N o n - S w i t c h i n g Amplifier ( N S A ) — T r a d e m a r k of Pioneer The circuit consisting of Q 4 1 1 , Q 4 1 3 , Q 4 1 5 , Q 4 1 7 , R 4 2 5 in Fig.

  • Page 12: E) Non-Switching Amplifier (With A Dc-Servo Circuit)

    e) Non-Switching Amplifier (with a DC-servo circuit) This amplifier has an operational amplifier (op amp) in voltage and stabilizes the amplifier's operation. As a addition to the above. Q33 amplifies only D C and ex­ result, the D C gain becomes lower t h a n 0 dB (smaller than tremely low frequency components, feeds it back 1 ) .

  • Page 13: Operation Of N S A H

    2, Operation of NSA Because of the demerits of class A amplifier explained a) Operation of Class-A and Class-B amplifiers above, most of the amplifiers produced today are class-B. W h e n the bias current of a transistor is adjusted to make However, in class-B operation, o u t p u t transistors are the average collector current half of its maximum, the driven in the range including the non-linear range, and...

  • Page 14: B) Switching Distortion

    b) Switching distortion In case of transistors which handle large a m o u n t of cur­ signal variation in the high frequency range and stagnates at the base. A n d the corrector current distorts as shown r e n t , such as o u t p u t t r a n s i s t o r s ,...

  • Page 15: C) Biasing Nsa

    d) Circuit of NSA (A-7) c) Biasing NSA Non-switching amplifier has voltage detectors which sense Switching distortion is inevitable as long as an amplifier the voltage exceeding 0.6V, increase bias voltage ( V is driven in class-B m o d e . To avoid it, NSA has been ) in proportion to the increase of the emitter voltage developed.
  • Page 16 Fig. 2 2 Potential with no input Fig. 2 3 Momentary potential at positive peak, 7 0 W output...
  • Page 17 (2) In Fig. 26, (1) has been simplified. This has been employed in A - 5 , A-6, SX-5, SX-6, SX-7, etc. (3) In Fig. 27, power is supplied from voltage-regulated power source. This has been employed in A-60, A-70, A-80, A-90, etc. constant current circuit Fig.
  • Page 18 -Constant voltage HF phase 2nd stage HF phase HF phase NSA bias & decoupling compensation Decoupling compensation compensation Pre-drive circuit Decoupling Output Q 3 ' s Impedance Q5 & Q7 bias — conversion Protection setting HF phase compensation HF phase Input compensation Overload...

  • Page 19: F) Operation Of D C Servo Circuit • 1

    f) Operation of DC servo circuit g) Operation of A - 7 Fig. 29 shows the basic structure of an amplifier with a The servo circuit of A-7 consists of Q33 and its surround­ D C servo circuit which is added to the ordinary D C power ing components.
  • Page 20 The gain of the amplifier in Fig. 32 is determined by (Ri + R2)/Ri. In Fig. 33, t h e reactance of C2 becomes in­ finite when the signal frequency decreases t o 0Hz (DC). Then the gain of Q33 becomes lOOdB (open gain of Q33) and t h e output becomes almost equal t o V ( + or - 14V).

  • Page 21: Circuits Of Special Function 1

    3. Circuits of Special Function a) Differential amplifier Fig. 35 shows a typical differential amplifier composed Thus in a differential amplifier, Qi a n d Q work as a see­ of two transistors of equal characteristics and three saw and even a very small level difference between the resistors.

  • Page 22: B) Cascode Amplifier

    b) Cascode amplifier Further, by connecting as shown in Fig. 39, the distor­ tion caused by D C voltage fluctuation between collector and emitter ( V c e ) can be minimized, and the V e of Qi can be adjusted by varying V c e of Q 2 . This connection makes it possible to use transistors of low withstanding- voltage and good characteristics.
  • Page 23 In Fig. 41 (a), when the base potential is made constant with Ri and D , a constant current flows in the transistor. If the constant current circuit is used as the load for a transistor, the characteristic of Fig. 41 (b) can be obtain­ ed.

  • Page 24: D) Bootstrap Circuit

    A n d Q2 s actual load impedance (R i2') is: R:o (hies + hfe-hie Rio + (hie3 + hfe-hie constant-current following stage circuit because the combined impedance of Q and Q 5 is - j - ^ - y If h i e : 2500 h i e...

  • Page 25: E) Darlington And Complementary Connections

    Zie3 Rie3 = hie3 + hfe-hie5 = hie3 + hfe-hie5 + hfe RI2' = BI2- = + hfe^-RL R 1 1 Z i e 3 R 1 0 + Rie3 R11 + Zie3 Fig. 4 8 Load of Q2 with bootstrap circuit Fig.

  • Page 26: F) Current Mirror Circuit

    R b i should be made lower t h a n R b 2 (about Ikfi) to keep f) Current mirror circuit the balance of base potential. T h e input impedance of The current mirror circuit, consisting of four transistors a transistor itself is low because it allows base current to and three resistors, is shown in Fig.

  • Page 27: G) Parallel Push-Pull Circuit

    g) Parallel push-pull circuit transistors of equal characteristics in parallel to the or­ To increase the power of an amplifier is to increase the dinary S E P P circuit as shown in Fig. 54 (b), the current current in power transistors and speakers. The parallel in the load can be divided into t w o and the current in push-pull circuit has been developed to increase the power each transistor can be made half of that in the load.
  • Page 28 push connection a n d feeding half of the load current t o Generally, the characteristics of hfe and f (transition fre­ a power transistor. When the current is divided into t w o , quency) versus collector current are not linear as shown the current variation per transistor becomes half, and the in Fig.
  • Page 29 Drive stage Input stage Output stage Pre-drive stage Standard SEPP amplifier All-stage direct-coupled SEPP amplifier All-stage direct-coupled SEPP DC amplifier N o n - S w i t c h i n g amplifier...

  • Page 30: Troubleshooting Guide

    II. Troubleshooting Guide 2. How do Troubles Occur? Checking circuits or components at r a n d o m on com­ plicated circuit boards is inefficient and time wasting. a) How are transistors damaged? With an N S A in particular, replacing only one faulty As seen above, in power amplifiers, transistors, especially component while neglecting to check others will not solve power transistors, are most likely to be damaged.
  • Page 31 With aluminum heat sink Ideal heat sink without heat sink Ambient temperature Area of heat sink (cm Fig. 6 1 Area of heat sink versus collector dissipation Fig. 6 0 Ambient temperature versus allowable collector dissipation (Pc) Thermal resistance is the resistance of a material to the conductivity of heat.
  • Page 32 The power transistors in a class-B amplifier are also heated by t h e storage effect of electrons, a n d wear o u t IC MAX (Pulse) fast when the operating frequency becomes high (20kHz single pulse — 100kHz). Refer to Fig. 6 3 . TC = 25°C IC MAX (continuous) Derating...

  • Page 33: B) The Mechanism Of Defects - H O W Are Amplifiers Damaged

    inductive reactance and capacitive reactance, and the Fig. 6 5 shows irreversible lc when V c e is increased and speaker load curve for a transistor makes a half ellipse. then decreased. Fig. 6 6 indicates that the higher the V c e and the longer the driving time, the smaller the A S O .
  • Page 34 C o m p o n e n t s i n t h i s a r e a b e c o m e C o m p o n e n t s i n t h i s a r e a a r e d a m a g e d d e f e c t i v e a c c i d e n t a l l y m a i n l y d u e t o e x t e r n a l c a u s e s .
  • Page 35 If this is C-E short-circuited at first Fig. 71 Process of damage The other causes of output transistor damage and fuse f. Q 2 5 , Q 2 7 , R51, R53, R45 a n d / o r R47: Open blow-out a r e : When Q 2 5 opens for example, Q 2 i ' s base potential becomes equal to that of...
  • Page 36 Auto Output...

  • Page 37: Troubleshooting Knowhow

    3* Troubleshooting Knowhow D C potential and continuity of circuits a n d components The means of troubleshooting power amplifiers are: with a multimeter. a. Measuring D C voltage with Multimeter (digital Audio generator and oscilloscope are for observing symp­ voltmeter).
  • Page 38 Applying audio signal Checking primary current Applying audio signal (after the faulty components have Checking primary current is a very effective way of been replaced) is normally performed to confirm whether avoiding further damage when confirming defect before the amplifier has been properly repaired. repairing, and when checking the amplifiers's condition after faulty components have been replaced.
  • Page 39 It must be noted that the same symptom may appear circuit, is faulty. when other block(s), such as power supply or protection Fig. 77 and Fig. 78 show examples. Power amplifier Power supply Power transformer Anyone of these can blow fuse w h e n faulty Fig.
  • Page 40 If the reading is still 0 0 , the power amplifier block is faul­ T o find out which block is faulty, check the continuity ty. In this case, there is a possibility that the power supply between the collectors of the output transistors ( + B and block is also faulty.
  • Page 41 Power amplifier Protection Ass'y Power amplifier L ch- Power amplifier R ch L ch output R ch output To power supply circuit Fig. 8 0 Finding faulty block — No sound POWER ON ' + B : + 4 7 . 5 V - B : - 4 7 .
  • Page 42 value before the voltage reaches 10% of the rated voltage. Gonfirming symptom with a Voltage Regulator If so, it automatically means that there is a defect in the As mentioned, confirming the symptom is essential before amplifier that may damage other normal components. starting repairs.

  • Page 43: Troubleshooting Power Amplifier

    4. Troubleshooting Power Amplifier in the input and the next two stages theoretically and prac­ tically as shown in Fig. 83. Troubleshooting the power amplifier is started after Therefore, t o save time, it is i m p o r t a n t to narrow down power supply and protection circuit are confirmed to be the area to be checked by confirming the symptom as OK.
  • Page 44 Amplifier Faulty Primary current Primary current normal but no excessive sound Disconnect secondary wind-" Power transformer Center voltage: Check Qn or pro­ ing of transformer. faulty (layer- O V ? tection circuit Current still shorted) excessive? Reconnect secondary winding Check voltage at every point in Disconnect ±...

  • Page 45: A) Primary Fuse Blows Out

    a) Primary fuse blows out. Possible causes; Output stage Both transistors short-circuited. Driver stage C-E shorted o n both channels. Pre-driver stage Q i s a n d C-E Shorted. Biasing circuit Q17 a n d / o r Q 1 9 Opened Q 2 1 a n d / o r Q 2 3 C-E Opened...
  • Page 46 Steps As mentioned, although the driver and power transistors Another thing to be noted is that there might be secon­ are most likely to be damaged, do not turn the power dary damage, namely, some other components might on right after replacing them. They could be the secon­ have been damaged by the excessive current.
  • Page 47 Inspection after replacing components do not get hot. Then, connect a load to the amplifier and After replacing faulty components, check and confirm confirm that n o distortion nor oscillation appears at the the potential at the points indicated in the circuit diagram, rated output.

  • Page 48: B) Fuse Is All Right, But No Sound

    b) Fuse is all right, but no sound. Possible causes: Suspected components: D C offset voltage appears on the center line, pro­ In this case, unlike in the case of blowing fuse, one of tection circuit works and protection relay stays off. the differential amplifiers from input to pre-driver stage ii) Although D C offset voltage o n the center line is OV, might be out of balance.
  • Page 49 Steps (1) Since diagnosis of this fault is performed mainly by (2) Then measure the D C voltage on the center line. checking voltages on the various points in the circuit, The next step to be performed depends on the value the DC-supply voltages must be first confirmed to or polarity (Refer to Fig.
  • Page 50 (1) When D C offset voltage is positive: shorted shorted open open shorted open shorted Auto Output open Fig. 9 0 Suspected components in the case DC offset voltage is positive. Fig. 90 shows the suspected components in the case D C Center line offset voltage is positive.
  • Page 51 (2) When D C offset voltage is negative; open. open .shorted open open shorted shorted Autoc 3 Output -47.5V Fig. 9 2 Suspected components in case DC offset v o l t a g e is negative Fig. 92 shows the suspected components when D C off­ set voltage is negative.
  • Page 52 (3) N o sound although the voltage on the center line is almost OV and protection relay turns o n . Auto Output Fig. 9 3 Suspected components of " N o sound although Protection Relay turns o n . " The cause of this trouble is Q n C-E open as shown in off.
  • Page 53 In case of A - 9 C h e c k components in this area Check components in this area when trouble is "No sound" when trouble is "Blowing fuse"...

  • Page 54: C) Other Troubles

    c) Other troubles Points to be checked: We have discussed how to trouble shoot the typical causes If distortion is easily audible, check bias voltage on of " F u s e blows o u t . " and " N o s o u n d " of N S A . Here, every stage.
  • Page 55 * 1 cause of shorted. Auto Output shorted cause of * 2 cause of Fig. 9 6 Suspected components in the case output distorts DISTORTION Vary signal level. Distorts at low signal Distorts at high signal level. level. Distortion depends on signal level? Distorts at every signal level.
  • Page 56 Oscilloscope Millivolt meter Distortion waveform Oscilloscope Distortion meter Power amp O U T Audio generator resistor Fig. 9 8 Confirming output Note After replacing transistors and other faulty components in bias or driving stage, be sure to adjust idle current to prevent crossover distortion or overheating of transistors.

  • Page 57: Noise

    2) Noise Troubleshooting: Causes: W o r n out 1st stage transistor. Normally, when transistors are w o r n out, their heat ap­ Faulty electrolytic capacitor. pear to be corroded in black. iii) Nearly shorted or opened component or pattern, In this case, the corrosion may have penetrated inside, poor soldering, or p o o r contact of switch.

  • Page 58: Intermittent Sound When Sound Level Is Low

    Fig. 1 0 0 Protection circuit 4) Click noise when powered o n / o f f 3) Intermittent sound when sound level is low Cause: Causes: Faulty muting circuit P o o r contact(s) of relay. ii) Nearly opened switch, leads or wires. The delay time of protection circuit is normally 5 - 1 0 seconds.

  • Page 59: Amplifier Becomes Hot Even When The Sound Level Is Low

    5) Amplifier becomes hot even when the sound level is low. In m a n y cases when power transistors become hot, Causes: power transformer also becomes hot. I m p r o p e r adjustment of idle current iii) Class-A amplifiers normally become hot irrespective ii) Faulty idle current circuit of the sound volume.
  • Page 60 Auto Output Fig. 1 0 3 S u s p e c t e d components in t h e case amplifier becomes hot...
  • Page 61 Dynamic Power Supply...
  • Page 62 CONTENTS OF DYNAMIC POWER SUPPLY E F F I C I E N T A M P L I F I E R 1. Why Is a Powerful Amplifier Required? 2. General Description 3. Calculating Dissipation II C I R C U I T P R I N C I P L E 1.

  • Page 63: Efficient Amplifier

    The performance of many other component parts should also be high. dynamic range. Pioneer has answered the requirement for more powerful With conventional amplifiers, we are still unable to have and energy saving amplifiers by developing the Dynamic the feeling of "presence"...

  • Page 64: General Description

    2 . General Description Conventional low-powered amplifiers can perform satisfac­ time and it becomes large only for a very short period, a torily if you d o not expect the reproduction of powerful few percent of the total period, a n d high-powered amplifi­ pulsive sound because music sound stays small most of the ers lose power idly in the other period.
  • Page 65 Fig. 3 shows the output waveforms of the voltage or cur­ The waveforms of output voltage (Vo) and the supply vol­ rent of Class-A and Class-B amplifiers. The collector dis­ tage (Va) of the D P S amplifier are shown in Fig. 4. sipation of Class A and Class B amplifiers will be discussed later.

  • Page 66: Calculating Dissipation

    To obtain the value of the whole dissipation in the output 3. Calculating Dissipation stage, the above result should be doubled because it relates only to the positive side of the push-pull circuit. In D P S Let's see how to calculate the dissipation under various con­ amplifiers, another dissipation in the power regulating tran­...

  • Page 67: Circuit Principle

    CIRCUIT PRINCIPLE Fig. 6 shows another simplified diagram of DPS. The sup­ ply voltage to the power stage (Va) is compared with the Power amp output voltage (Vo) and is controlled by the Differential Differential amp Detector. With an additional offset voltage, Va is main­ tained higher than Vo when the input and output signals are high.

  • Page 68: A) When No Input Signal Is Applied

    and Q5. The circuit responds in real time having no capa­ Vd is determined by the 6.2 V zener voltage and the ratio citor in the loop. Q19's V B quickly follows the variation of R49 to R44. R106 of 47fl is negligible. Vd has been set of Q21's V B .
  • Page 69 b) When DPS starts working with 8Q speaker (load) • connected Q 2 1 ' s VB rises and Q 2 1 turns on when the output voltage shows the voltage and current readings in the circuit and reaches a threshold level. Q 2 1 ' s Vc drops, and Q 1 0 1 and Q 5 the waveforms of Vo and Va at the moment Q 1 0 1 and Q 5 are turned on because their VBES are increased.

  • Page 70: C) When Speakers Are Disconnected

    c) When speakers are disconnected. V L becomes 59.6 V when the speaker circuits are opened the speakers are disconnected. The DPS amplifier, however, because no current flows in R105. Fig. 11 shows the vol­ works when the input signal is increased and Va rises even tage and current readings in the circuit at the time when if the load is disconnected.
  • Page 71 Fig. 12-a Voltage and current reading when producing 1 5 0 W signals Fig. 12-b Output and power supply voltage waveforms...

  • Page 72: E) When The Output Power Is 120W (80 Load)

    e) When the output power is 120W(8tt l o a d ) . The voltage and current become as shown in Fig. 13. The combined hfe of Q5 and Q101 is 7,260. Fig. 13-a Voltage and current readings when output is 1 2 0 W signal Fig.

  • Page 73: H I G H - O N Circuit

    2. H I G H - O N Circuit (For H i g h Frequency) Fig. 14 Dynamic power supply circuit of A - 8 0 When a signal above 3kHz appears at the output, it is smoothed by R47, C14 and R48, turns Q23 off and Q25 and Q26 on, and shifts Va from V L to V H even if the Vo is lower than the threshold V H of the Differential Ampli­...
  • Page 74 The circuit a n d frequency characteristic of the high-pass filter composed of R47, C14 and R48 is shown in Fig. 16. High-pass filter Fig. 16 Characteristic of High-pass filter With the voltage indicated in Fig. 14, Q23 in the H I G H - O N circuit is usually on, Q24, Q25 a n d Q26 are off.

  • Page 75: Maintaining Vh By H I G H - O N Circuit

    Fig. 18 Threshold level VS output frequency 2-1 Maintaining VH by H I G H - O N circuit After H I G H - O N circuit is activated, the V H level is main- been indicated in Fig. 17. The potential at © drops gracju- tained for (B) msec by the RC time constant to prevent the ally as shown in Fig.

  • Page 76: Function Of Each Component In H I G H - O N Circuit

    2 - 2 Function of e a c h c o m p o n e n t in H I G H - O N circuit Fig. 2 0 Voltage and current in H I G H - O N circuit •R63 (15 kfl) To make the operation of Q23 stable, its V E is made cons­...

  • Page 77: Troubleshooting

    III. TROUBLESHOOTING As explained, the D P S amplifier is highly efficient because it is usually driven by a low voltage supply and is driven by a high voltage supply only when the input signal is high. The D P S circuit seems to be complicated because the dual power supply circuit is closely related to the power ampli­...
  • Page 78 a) The differential amplifier can be checked by applying an input signal lower than 2kHz because the H I G H - O N circuit becomes active when the frequency is more than 2kHz. Photo 3 Supply voltage made by Differential Detector b) The H I G H - O N circuit can be checked by setting the in­...

  • Page 79: Cause And Effect

    The transistor's VBE increases. It turns on. The VEBS of Q101 and Q5 decrease. They turn off and block V H In A-60 and A-80, when the impedance switch is on the supply. 4-6fi side, the output signal current to the D P S circuit is blocked by the impedance switch.

  • Page 80: Va Stays At V H All The Time

    Va stays at V H all the time. a) R101(102) open. 0101(102), Q5(7), and/or Q21(Q22), ce short-circuited (Vh on one side) •If Q21CE shorts ® , QlOl's V B falls (2), Q101 turns on, Q5's VEB increases, Q5 turns on (3) and Va becomes V H ®.

  • Page 81: Differential Detector Is Inactive (Va Stays At Vl)

    2 - 3 Differential D e t e c t o r is inactive (Va s t a y s at VL). short-circuited, short-circuited, D18(19) Q19(20)ce Q21 (22) open •If Q19 short-circuits ® , Q19 V E rises (2), Q21 V E rises •If D18 short-circuits, Q21 VBE becomes 0 V, Q21 stays off ®...

  • Page 82: By-Running Va Is Not High Enough

    2 - 5 By-running V a is not high enough in the range w h e r e t h e Differential Detector works. D 1 5 (16) short-circuited The difference (Vd) between the output voltage (Vo) and NARROW by-runner (Va) depends on the difference of the base poten­ tial of Q19 and Q21, the zener voltage across D15 and the rate of the resistance of R44 to that of R49.

  • Page 83: Trouble-Shooting Flowchart

    3 . TROUBLESHOOTING FLOW CHART D Y N A M I C POWER SUPPLY R A T E D O U T P U T I S H E A T D I S T O R T I O N U N A V A I L A B L E .
  • Page 84 MEMO...
  • Page 85 M E M O...

  • Page 86: Fet Buffer Circuit (A-90)

    FET BUFFER CIRCUIT (A-90) Here, we will discuss A-90. A-90 employs an F E T buffer A-90 employs FETs of source-follower connection between circuit to get a high output with low distortion. Generally, pre-driver and power stages as buffers. The input im­ pedance of F E T is logically infinite and its output im­...
  • Page 87 NSA/DPS AMPLIFIERS A-60 A-70 A-90...
  • Page 88 SERVICE GUIDE TROUBLESHOOTING POWER AMPLIFIERS — SUPPLEMENT TO TUNING F O R K - First printing: March 1984 Compiled and edited by Editor in Chief: Ikki Nagashima Administration Department International Division Tadahiro Nakagawa Service Section Administration Department International Division Editors: H.
  • Page 89 5000, Airport Plaza Drive, Long Beach, California 90815, U.S.A. PIONEER ELECTRONIC (EUROPE) N.V. Keetberglaan 1, 2740 Beveren, Belgium PIONEER ELECTRONICS AUSTRALIA PTY LTD. 178-184 Boundary Road, Braeside, Victoria 3195, Australia Printed in Japan G G F - 6 0 1...

This manual is also suitable for:

A-70A-90

Table of Contents