BBK AV217 Service Manual

ENGLISH

AB217

SERVICE MANUAL

CONTENTS

NAME OF PINS I/O DESCRIPTION NUMBER OF PINS

VDD

P

DIGITAL POWER INPUT

1

XI N

I

OSCILLATOR INPUT

2

XOUT

O

OSCILLATOR OUTPUT

3

D1 / REQ

I

SIMPLE MODE: D1 DATA INPUT
MICRO CONTROL MODE: DEMAND
SIGNAL

4

D2 / SCK

I

SIMPLE MODE: D2 DATA INPUT
MICRO CONTROL MODE: TIME
PULSE INPUT

5

D3 / DATA

I

SIMPLE MODE: D3 DATA INPUT
MICRO CONTROL MODE: DATA INPUT

6

D4/IDSW

I

SIMPLE MODE: D4 DATA INPUT
MICRO CONTROL MODE:
IDENTIFYING CODE INPUT

7

TEST

I

EXCLUSIVELY FOR THE TEST. BE
GROUNDED WHEN IN DAILY USE.

8

EASY/ U- COM

I

HIGH POTENTIAL£ºSIMPLE MODE
LOW POTENTIAL: MICRO CONTROL
MODE

9

SLEEP

I

HIGH POTENTIAL£ºSLEEP MODE
LOW POTENTIAL: NORMAL MODE

10

D- GND

G

DIGITAL

11

A- GND

G

ANALOG

12

LPF2 OUT

O

LOW PASS FILTER 2 OUTPUT

13

LPF2 I N

I

LOW PASS FILTER 2 INPUT

14

OP2 OUT

O INTEGRATOR 2 OUTPUT 15

OP2 IN

I

INTEGRATOR 2 INPUT

16

CC2

\

CURRENT CONTROL 2

17

CC1

\

CURRENT CONTROL 1

18

REF

\

ANALOG REFERENCE VOLTAGE

£ ¨=1/ 2Vcc£ ©

19

OP1 I N

I

IN INTEGRATOR 1 INPUT

20

OP1 OUT

I

INTEGRATOR 1 OUTPUT

21

LPF1 OUT

\

LOW PASS FILTER 1 OUTPUT

22

LPF1 I N

O

LOW PASS FILTER 1 INPUT

23

Vcc

P

ANALOG POWER INPUT

24

FUNCTIONS OF THE PINS

- 27 -

1 Circuit Makeup.................................................................................................

Block Diagram...................................................................................................

2 Power Supply Circuit........................................................................................

3 Input Circuit.....................................................................................................

4 Volume, Tone and Balance Adjusting Circuits...................................................

5 Microphone Circuits.........................................................................................

5.1 Working Principle of the Front Processing Section..............................................

5.2 Working Principle of the Echo Processing Section...............................................

6 Front Panel Control and Display Circuits..........................................................

6.1 Input Control Section........................................................................................

6.2 Channel and MIC Delay Section.........................................................................

6.2.1 Channel Selection Section.............................................................................

6.2.2 The MIC Delay Selection Section....................................................................

6.3 The Spectrum Analysis Section.........................................................................

7 Power Amplification and Protection Circuits....................................................

7.1 Power Amplification Section..............................................................................

7.2 Protection Circuit.............................................................................................

7.2.1 Delay Switch-on Protection Circuit..................................................................

7.2.2 Midpoint Over-voltage Circuit.........................................................................

7.2.3 Short Circuit Over-current Protection..............................................................

7.3 Multi-channel Control Circuit............................................................................

8 Detailed Circuit Explanations...........................................................................

8.1 The Power Amplifying Board.............................................................................

8.1.1 Main Parts List of The Matin Power Amplifying Board........................................

8.1.2 Schematic Diagram Of The Main Amplifying Board...........................................

8.2 Front Panel's Control Board..............................................................................

8.2.1 Main Parts List of The Front Panel's Control Board...........................................

8.2.2 Schematic Diagram of The Front Panel's Control Board....................................

8.3 Potentiometer Board........................................................................................

8.3.1 Main Parts List of The Potentiometer Board.....................................................

8.3.2 Schematic Diagram of The Potentiometer........................................................

9 The Explanation For Key Components.............................................................

1
2
3
4
5
6
6
6
7
7
9
10
10
11
12
13
13
14
14
15
15
16
16
16
18
19
19
22
24
24
25
26

1 Circuit Makeup

This unit's circuit can be divided into six parts.

1.1 Source Circuit

Supplies power to each circuit unit.

1.2 Input Circuit

Selects one of four lines of input analog signals and sends it to the rear circuit.

1.3 Volume and Tone Adjusting Circuits

Adjusts master volume and treble and bass tone of input signals.

1.4 Power Amplification and Protection Circuits

Amplifies input signals' power to drive speakers to produce sound; Protects circuits of speakers
and power amplifier automatically in abnormal conditions.

1.5 Microphone Circuit

Adjusts volume and tone of signals from the microphone and superimpose them on left and right
channels after echo processing.

1.6 Main Board Control and Display Circuits

Receives control commands and send control signals to achieve control function. Drives the VFD
screen to show the current working mode.

9 The Explanation For Key Components

IC Sc6931P

VDD

1

XIN

2

XOUT

3

D1/REQ

D2/SCK

D3/DATA

D4/IDSW

EASY/U-COM

SLEEP

D-GND

A-GND LPF2 OUT

4

5

6

7

TEST

8

9

10

11

12 13

VCC

24

LPF1 IN

23

LPF1 OUT

22

OP1 OUT

21

OP1 IN

20

REF

19

CC1

18

CC2

17

OP2 IN

16

OP2 OUT

15

LPF2 IN

14

- 1 - - 26 -

8.3.2 Schematic Diagram of The Potentiometer

Circuit

Speakers

Power

Supply

RPH01A

B50K

RPH01B

B50K

R917

2.2K

R918

2.2k

XP7

1
2
3
4
5

5PIN

L2
R2

GND

R3
L3

R

Power

Left Channel's

RP902

L

Circuit

Protection

Amplification

Power

Right Channel's

Echo

N903

Amplification

RPH01

Balance

Tone

N902

RP903

Adjustment

N901

Buffer

Amplification

C

SR

SL

and

2 CH

5 CH

Switch

BLOCK DIAGRAM (Figure 1)

Amplification

Echo

N905

SC6931

N906A

Amplification

Level Sampling

VFD

Screen

Echo

V601

Processing

Signal

Amplification

Tone

RP603

RP604

N906B

Adjustment

MIC Muffling

N601A

N601B

Level

Master

RP901

Volume

Adjustment

L

REC

R

Input

N401

CD4052

Selection

DVD

VCD

CD

TAPE

Spectrum

Front

Control

Panel's

Comparison

Function

Push

Matrix

Button

Two Lines

Amplification

Simultaneous

RP601

RP602

Volume

Adjustment

MIC1

MIC2

OK-SW

- 2 -- 25 -

2. Volume adjustment, sound field processing and EQ adjustment
circuits.

All channel signals are sent to N402 inside which the independent volume adjustment,
EQ adjustment and all sound field modes process are performed.

The sound field processing and EQ adjusting circuit is mainly processing the L&R
channel signals. According to the schematic diagram, the L&R channel signals are
added simultaneously to the pins 15, 17, 13 and 16 of N402. When the unit mode is in
the Hi-Fi mode, the internal circuit of the pins 17&16 is connected and the other input
signals are cut off. At this time, only the L&R channel volume can be adjusted and only
the pins 31&32 send out signals. Therefore, the unit is in the 2CH output mode. The
unit mode is not in the Hi-Fi mode, other input signals are connected but the pins
17&16 signals are cutoff. At this time, all channel volumes can be adjusted
independently and the sound field processing or EQ adjusting of the L&R channels
can be performed. Finally, all channel signals pass out from the pins 31, 32, 33, 34,
35&36. The SW channel signal from the pin 36 reaches the amplified speakers to be
amplified through the SW output terminals. Other channel signals reach to the power
amplifying circuit to be amplified. The L&R channel signals will go through 1 grade
LPF and MIX amplification (Karaoke signals are overlapped into L& R channels).

st

3. Input signals detect, search and frequency spectrum sampling cir
cuits

3.1 Input signals detect and search circuit: The six channel signal lines of the input IC
N402 are connected with 100K sampling resistors R533, R534, R657, R676 and R678
respectively. The signals are mixed by these resistors and added to the opposite-phase
input terminal to be amplified. VD431 and C481 connected to N403B's output end
constitute half-wave rectifying filter circuit. Then the signals reach the voltage comparer
composed of N403A. The output end of N403A (SEARCH)is connected to the pin 28 of
CPU. This control signal is the search and detect signal: when it is low level, it enters the
search mode; when it is high level, it stops searching. Its works as follows:

3.1.1 When this unit is getting started, the A&B control signals from the pins 38&39 in
the domination of the CPU's inter program are added to the input select circuit to
search circularly once. When there are no signals in these four input connectors, the
VCD mode stops automatically. When there are signals in one of the four connectors,
AC signals will appear in all channels of the input N402. These AC signals are
amplified by N403B and rectified and filtered by VD434 and C481 to become DC
signals. At this time, the opposite-phase voltage of N403A is 0.01V. When this DC
voltage surpasses 0.01V, the output end of N403B sends out a high level (SEARCH)
close to positive power supply voltage (A+6V) which reaches the pin 28 of CPU. CPU
keeps searching in the connector in which there are input signals and the unit will play
normally.

1.2.2 When press the SEARCH on the front panel, CPU sends out A&B control
signals again to start searching. Meanwhile, the pin 27 (EX) sends out a high level
which makes V446 inductive. The emitter of V446 sends out a high level which passes
through R498 which makes the opposite-phase voltage of N403A to be 0.4V. That is
to say, if you want to stop searching of CPU, the gained voltage after the input signals
are rectified and filtered must exceed 0.4V. This voltage is higher than 0.01V when
this unit is getting started in order to avoid that the CPU receives signals mistakenly
and stops searching due to the large external interference signals. If the input signals'
amplitude is not high enough, CPU will continue searching. When the amplitude is
high enough, N403A sends out high level to the pin 28 to stop searching. The pin 27
(EX) will become low level again and the opposite-phase voltage of N403A will also
returns back to 0.01V. The whole searching process is finished.

- 3 - - 24 -

R640

4.7k

L4

1

101

4558

-12V
N903A

C911

R921

27K

N902B

R908

10K

TREBLE

RP903A

B50K

R907

10K

10k

R905

8 4

3

2

+12V

R920

27k

R919

10k

R2L2L3R3GND

12345

XP7

T obanlance B o ard

7

4558

C907

101

5

6

R911

10K

C905

152

BASS

R909

22K

C906

683

B50K

RP902A

R910

10K

C903

1u/16V

7

N901B

4558

6

10k

R901

RP901A

10k

R906

5

R903

100K

B50K

123

XP4

3PIN

L1

R1

GND

To AMP Board

R924

101

C912

5PIN

+12V

84

R913

10K

RP903B

B50K

TREBLE

R912

10K

C901

-12V

C952

B50K

RP901B

R4

R926

100k

R925

100k

7

27k

4558

N903B

5

6

R923

27K

R922

10K

1

N902A

4558

-12V

C910

101

3

2

R916

10K

C908

152

BASS

R914

22K

683

C909

B50K

RP902B

R915

10K

C904

1u/16V

47u/16V

1

C902

N901A

4558

47u/16V

8 4

C913

+12V

3

2

C953

104

104

R904

100k

10K

R902

R4

12345

XP5

R4

2

N906A

101

R927

470k

-12V

C914

-12V

+12V

L4

6

6PIN

L4

-12V

+12V

GND

To AMP Board

+12V

VD602

1N4148

R643

10k

1k

R642

C636

4.7u/16V

R644

47k

C616

C614

4.7u/16V

C615

R619

15k

+5V

3

4558

8 4

+12V

1

4u7/16V

C603

101

LEVEL

C601

RP601

9014

V601

R641

C635

3.3k

R621

4.7u/16V

4.7u/16V

10k

R620

C630

47u/16V

R635

+12V

C605

47k

R603

-12V

C604

1k

R601

10u/16V

C50K

123

XP6

MIC1

R639

8.2k

R637

220k

R638

C633

4.7u/16V

470u/16V

R624

12K

562

C618

R622

10k

R623

15k

C619

104

561

C617

24

23

21

L1 IN

VCC

L1 OUT22O1 OUT

N905 SC6931

VDD1XIN2XOUT3D1/REQ4D2/SCK5D3/DATA6D4/IDSW7TEST8EASY/CM9SLEEP10DGND11AGND

30p

C628

2M

G601

30p

C629

C631

103

5.1V

VD601

150/0.5W

R618

47k

1

104

N601A

4558

C607

8 4

3

2

C606

47uF/16V

1k

R602

C602

10u/16V

C50K

RP602

4

4PIN

MIC2

GND

K-MUTE

Fr omMI Bo ard

C634

10u/16V

5.6k

100k

R625

10k

C620

20

O1 IN

104

+12V

47uF/16V

47u/16V

C621

REF19CC118CC2

B50k

RP605

4.7k

R946

10k

R636

C627

C623

4.7u/16V

C632

C625

R626

15k

224

C622

224

104

C624

17

16

15

O2 IN

O2 OUT

R634

10k

150mS

180mS

N906B

R610

8.2k

R609

20k

TREBLE

RP603

R608

12k

C610

R607

1.5k

R606

3.9k

10k

R604

C608

103

4.7u/16V

562

10k

15k

2.2k

R629

R628

R627

561

C626

14

13

L2 IN

L2 OUT

12

R630

10k

R631

10k

R632

10k

10k

R633

7

NJM4558

47p

R617

470k

C613

5

6

R616

10k

20k

R615

4.7k

8.2k
C612

104

R611

R612

BASS

B20k

RP604

B20k

471

C611

R614

10k

R613

123

C609

10k

7

N601B

47p

NJM4558

5

6

R605

100K

10u/16V

47

CD

CD11C 50V1U±20%4×7 1.5 C903,C904,C941

48

CD

CD11C 50V10U±20%5×7 2 C601,C602,C608

49

CD

CD11C 16V47U±20%5×7 2 C620,C630

50

CD

CD11 35V220U±20£¥10× 15
5

C956,C947

51 DIODE 1N4004 VD912,VD914
52 DIODE 1N4148 VD903~VD911,VD916,VD602

53

VOLTAGE
REGULATOR
DIODE

5.1V 1/2W VD601,VD915

54

VOLTAGE
REGULATOR
DIODE

24V 1/2W VD913

55 TRIODE 2N5551 V901
56 TRIODE 9014C V601
57

IC

LM324N DIP N907,N910,N911,N912

58

IC

NJM4558D DIP N901~N903,N906,N601

IC

4558C DIP N901~N903,N906,N601

59

IC

CD4013BCN DIP N908

60

IC

SC6931P DIP N905

61

CRYSTAL
OSCILLATOR

2.00MHz 49-U G601

62 VFD YW-3707A VFD901

63

LIGHT
TOUCH
RESTORE
SWITCH

VERTICAL 6×6×1 S901~S906

64

PCB

9217-4

65

CONNECTION
CORDS

¦µ

0.6 SHAPED 7.5mm

W1~W4,W7~W9,W11~W13,W16,W19~W22,W29,
W31~W34,W37,W38,W43,W46,W49,W52,W54,
W56~W58,W62,W65~W69,W74,W75,W81,W82,W83,
W90~W93,W99,W102,W103,W114,W116,W117

66

CONNECTION
CORDS

¦µ

0.6 SHAPED 10mm

W5,W17,W18,W23~W28,W35,W36,W39,W40,W42,
W47,W48,W59,W64,W70~W72,W76,W84~W86,W94,
W95,W98,W100,W101,W104,W109~W112,W115

67

CONNECTION
CORDS

¦µ

0.6 SHAPED 12.5mm

W10,W14,W15,W30,W44,W51,W61,W77,W78,W88,
W89,W107,W108,R1013

68

CONNECTION
CORDS

¦µ

0.6 SHAPED 15mm

W6,W41,W45,W50,W53,W55,W60,W63,W73,W79,
W80,W87,W96,W97,W113

69

CONNECTION
CORDS

¦µ

0.6 SHAPED 20mm

W105,W106

CORDS 24# 50mm BLACK

70 RAFT CORDS

3P360 2.5 2 PLUG WITH L
NEEDLE

XP3

71 RAFT CORDS

5P60 2.5 2 PLUG WITH L
NEEDLE

XP7

72 RAFT CORDS

3P80 2.5 2 PLUG WITH L
NEEDLE

XP2

73 RAFT CORDS

3P360 2.5 2 PLUG WITH L
NEEDLE , 2P SHIELDED

XP4

74 RAFT CORDS

4P60 2.5 2 PLUG WITH L
NEEDLE, 3P SHIELDED

XP6

75 RAFT CORDS

6P360 2.5 2 PLUG WITH L
NEEDLE, 2P SHIELDED

XP5

76

SOFT SPONGE
SPACER

10×10×5 DOUBLE
FACED, HARD

VFD/PCB

8.2 Front Panel's Control Board

NO. DESCRIPTION

SPECIFICATIONS / PART

NUMBER

LOCATION SPECIFICATIONS

1

CARBON FILM
RESISTOR

1/4W470¦¸±5% SHAPED
10

R979,R990,R994,R997,R1000,R1003,R1006,R1009,R1010

2

CARBON FILM
RESISTOR

1/4W1K±5% SHAPED 10

R601,R602,R961,R964,R967,R970,R982,R988,R1016,
R1012,R1007,R985,R1014,R642

3

CARBON FILM
RESISTOR

1/4W1.5K±5% SHAPED 10 R607

4

CARBON FILM
RESISTOR

1/4W2.2K±5% SHAPED 10 R629,R1004,R977,R978

5

CARBON FILM
RESISTOR

1/4W3.3K±5% SHAPED 10 R991,R621

6

CARBON FILM
RESISTOR

1/4W3.9K±5% SHAPED 10 R606

7

CARBON FILM
RESISTOR

1/4W4.7K±5% SHAPED 10 R1001,R611,R946,R640

8

CARBON FILM
RESISTOR

1/4W5.6K±5% SHAPED 10 R639

9

CARBON FILM
RESISTOR

1/4W10K±5% SHAPED 10

R901,R902,R905~R908,R910~R913,R915,R916,R919,
R922,R957,R971,R989,R995,R981,R987,R1015,R604,
R613,R614,R616,R620,R622,R625,R627,R630~R634,
R636,R643

10

CARBON FILM
RESISTOR

1/4W12K±5% SHAPED 10 R608,R624

11

CARBON FILM
RESISTOR

1/4W15K±5% SHAPED 10 R623,R626,R628,R619

12

CARBON FILM
RESISTOR

1/4W20K±5% SHAPED 10 R975,R976,R609,R615

13

CARBON FILM
RESISTOR

1/4W22K±5% SHAPED 10 R993,R996,R999,R1002,R984,R1008,R1005,R909,R914

14

CARBON FILM
RESISTOR

1/4W47K±5% SHAPED 10 R973,R974,R980,R983,R959,R960,R603,R618,R644

15

CARBON FILM
RESISTOR

1/4W100K±5% SHAPED10R903,R904,R925,R926,R962,R965,R968,R972,R963,

R966,R969,R992,R958,R605,R638

16

CARBON FILM
RESISTOR

1/4W220K±5% SHAPED
10

R1011,R637

17

CARBON FILM
RESISTOR

1/4W470K±5% SHAPED
10

R927,R617

18

CARBON FILM
RESISTOR

1/4W30K±5% SHAPED 10 R920,R921,R923,R924

19

CARBON FILM
RESISTOR

1/4W8.2K±5% SHAPED 10 R998,R610,R612,R641

20

CARBON FILM
RESISTOR

1/2W2K±5£¥ SHAPED 12.5

R986

21

CARBON FILM
RESISTOR

1/2W150¦¸±5% SHAPED

12.5

R635

22

ROTATING
POTENTIO­METER

A145GOED-H1B503-007 RP901

ROTATING
POTENTIO­METER

A145GOED-H1B503-007­01

RP901

ROTATING
POTENTIO­METER

A145GOED-H1B503-007­02

RP901

23

ROTATING
POTENTIO­METER

A145GOED-H1B503-008 RP902,RP903

8.2.1 Main Parts List of The Front Panel's Control Board

1. A+25V passes C941 and R983 and adds an instantaneous high level at the Pin 12 of
N907D when this unit gets started. According to the above characteristics, the Pin 14 sends
out a voltage which is comparatively closer to the voltage of the power supply B+23V. This
voltage measures about +17V and is fed back to the Pin 12 through R960. Then this voltage
is divided into about +8.5V by the resistor R959. That is to say, the inphase voltage of the
calculating amplifier N907D keeps at about +8.5V. At the same time, +8.5V is divided by
VD903, R971 and R972 and the voltage of the Pin13 of N907D measures about +7.5V. That
is to say, the inphase opposition of N907D keeps at about +7.5V. At this moment, the inphase
voltage (ca +8.5V) of the calculating amplifier N907D is higher than the inphase opposition
voltage (ca +7.5V). The output Pin 14 also keeps at about +17V. Therefore, the above status
retains. The Pin 14's high level of +17V passes R961 and reaches the display screen and
lightens the VCD indicator. The 0 level is obtained at the controllers A&B of the electronic
switch in the input circuit. According to the real value table, the electronic switch elects the
VCD input mode. C941 is the open restoration capacitor because of which the input mode
is switched to the default VCD. The inphase opposition voltage of another three calculating
amplifiers is +7.5V (Their inphase opposition ports are connected together), but the positive
voltage doesn't exist in the inphase ports. According to the voltage comparing characteristics,
there is not the high level output in the inphase opposition ports. The other three input modes
are shut off.

2. When we select other input modes, for instance, selecting DVD mode, we press the switch
S903. The voltage of B+23V passes R984, S903 and R965 and is divided into about +18V
voltage which is sent to the inphase port of N907A. At the same time, the +18V voltage is
divided by VD905, R971 and R972 and there is about +17V level input at the inphase
opposition port of N907A. The high level from N907A is fed back by R966. When loosening
S903, N907's working voltages (The working principle is the same as that in the above­mentioned VCD mode.) are as follows: +8.5V at inphase port, +7.5V at inphase opposition
port, +17V at output port. As mentioned before, the inphase opposition port's voltage is +17V
when the switch is turned on. This voltage also reaches the calculating amplifier N907 in the
VCD mode. Because the inphase port of N907D remains +8.5V and the inphase opposition
port increases to +17V, the original output mode is breached and the high level cannot be
sent out. Therefore, the VCD mode is shut off. At this moment, the high level of +17V of
N907A's output is divided into two lines: One line is sent to the display screen by R967 to
lighten the DVD indicator. Another line is divided by VD908, R974 and R975 and sent to the
Port B of the electronic switch in the input circuit. Now, the Port A of N401 is 0 level and the
Port B of N401 is 1 level. According to the real value table, the electronic switch selects the
DVD mode, and the whole process is finished. When selecting other modes and pressing
other switches, the caused motions are the same as above ones.

- 8 -- 19 -

6.2 Channel and MIC Delay Selection

The delay circuit is made up of the D triggers N908A, N908B and voltage comparers N910B,
N910C, N911A. The inching switch S905 is the channel selection button in the front panel.
S906 is the MIC delay selection button.

The Real Value Table of the D Trigger

Input Port

CLK

/

/

D

0

1

0

R

/

0

0

0

0

D, R and S are the controllers. It's low level when R is grounded. CLK is the triggering port
whose output mode overturns when a high level comes. When A+25V passes through R980
and R991, the inphase opposition voltage of those four voltage comparers is divided into
about +1.6V. The working modes are as follows. (Figure 8)

Figure 8

S

1

0

0

0

Output Port

Q

1

1

0

1

~

O

0

0

1

0

R990

VD916

V-5CH

XP3

1

2

3

A

B

Ex

8.1.2 Schematic Diagram Of The Main Power Amplifying Board

L

R

V427

C9014

V426

Y401

1 2

3 4

1N4148

VD418

VD405

1N4148

C9014

V421

C411

1u/16V

+33V

R433

V409

D718

V407

2N5551

2N5551

V430

220

R459

R409

150

V404

2N5401

R404

4k7

R403

4k7

V401

2N5551

C439

47u/35V

C9014

DC 24V

1N4004

VD407

5 6

10k

VD409

12V

R448

R447

1M

R446

47k

R461

2.7k

R435

3.9k

R414

220

22k

R413

V402

2N5551

C417

10u/50V

C416

C415

220u/25V

V425

10k

C9015

10k

R445

V424

C9014

R444

10k

47k

R462

1k

R443

V423

C9014

VD406

1N4148

104

R439

10/2W

C413

3.9k

R434

V410

B688

-33V

R416

R415

0.25/3W

0.25/3W

C433

R411

C404

680

R408

C402

R402

C401

2N5401

V408

10p

3k

V406

33

C403

R405

10k

271

22k

10u/16V

V431

2N5401

R412

1.2k

C9014

C405

47u/25V

V403

220

R401

R460

R410

150

V405

2N5551

33

22k

R407

VD402

1N4148

VD401

1N4148

2N5551

R406

1k

C440

47u/35V

R4

L4

C436

C435

DC 24V

Y402

220u/25V

220

R463

C

10u/50V

10u/50V

123456

C412

1u/16V

+33V

2N5551

V432

220

R425

150

C441

47u/35V

220

R417

SL

SR

~25V

C438

10u/50V

C437

10u/50V

V422

C9014

D718

V419

2N5551

V417

V414

2N5401

R420

4k7

R419

4k7

C406

VD408

1N4004

C418

100u/35V

V435

VD419

1N4004

V434

C9014

R442

10k

R441

10k

R440

10/2W

2.7k

R438

3.9k

R436

V412

V411

10u/16V

R437

R431

R432

0.25/3W

0.25/3W

R430

220

10p

C434

22k

R429

3k

R427

R428

1.2k

C409

33

V416

C9014

C410

680

2N5551

R424

C408

47u/25V

10k

R421

271

C407

2N5551

22k

R418

FL401

R450

47/3W

VD410

1N5404

C9014

220/3W

R451

R453

V428

2N5551

+12V

104

C414

3.9k

33

V413

-33V

B688

V420

V418

2N5401

V433

2N5401

R464

R426

150

V415

22k

R423

2N5551

VD404

1N4148

VD403

1N4148

2N5551

R422

1k

C442

47u/35V

From Tra ns

0

~25V

224

C420

C419

224

FL402

T6.3A/250V~

VD411

1N5404

C421

6800u/35V

+33V

C423

470u/25V

3k3

VD415

12V

C425

47u/16V

C427

100u/16V

220

+12V

6.8V

VD417

R4671kR4681kR4691kR4701kR4711kR4721kR4731kR474

VCD R

T6.3A/250V~

VD413

1N5404

VD412

1N5404

C422

6800u/35V

R452

220/3W

C424

-33V

470u/25V

R454

3k3

VD414

12V

V429

2N5401

C426

47u/16V

C428

100u/16V

-12V

XS4

102

C432

C431

1k

R4571kR458

1k

R455

C429

47u/16V

VCD L

3

X13Y

168

N401

CD4052

X012X114X215X311Y01Y15Y22Y3

4

CD L

CD R

DVD R

102

R 1

6A10B9

INH

DVD L

12345

6

XS5

6PIN

R4

L4

-12V

+12V

To VFD Board

123

L 1

To VFD Board

123

XS3

3PIN

VEE

7

VD416

TAPER

3PIN

A

B

Ex

R466

47K

R465

47K

C444

10u/16V

C443

10u/16V

1k

R456

-12V

6.8V

C430

47u/16V

1k

TAP EL

REC L

REC R

- 9 - - 18 -

6.2.1 Channel selection section.

30 CD CD11 25V220U±20%8×12 3.5 C415,C416
31 CD CD11 35V470U±20%10×20 5 C423,C424
32 CD CD11 50V1U±20%5×11 2 C411,C412
33 CD CD11 50V10U±20%5×11 2 C435,C436,C437,C438,C417
34 CD CD11 35V47U±20%6×12 2.5 C439,C440,C441,C442
35 CD CD11 35V100U±20%8×12 3.5 C418
36 CD

LUA 35V6800U±20£¥30×45 10

C421,C422
37 DIODE 1N4004 VD407,VD408,VD419
38 DIODE 1N4148 VD401~VD406,VD418
39 DIODE 1N5404 VD410~VD413

40

VOLTAGE
REGULATOR
DIODE

12V 1/2W VD415,VD414,VD409

41

VOLTAGE
REGULATOR
DIODE

6.8V 1/2W VD417,VD416

42 TRIODE 2N5401 V404,V408,V414,V418,V429,V431,V433

43 TRIODE 2N5551

V401,V402,V403,V405,V407,V411~V413,V415,V417,

V428,V430,V432

44 TRIODE 9014C

V406,V416,V421,V422,V423,V424,V426,V427,V434,V4

35
45 TRIODE 9015C V425
46 TRIODE KB688O V410,V420

TRIODE KB688Y V410,V420

47 TRIODE KD718O V409,V419

TRIODE KD718Y V409,V419
48 IC CD4052BCN DIP N401
49 RELAY JH4237-024-2H DC24V Y401,Y402
50 PCB

4217£-3

51

TERMINAL

SOCKET

AV6-8.4-3B XC2

52

TERMINAL

SOCKET

AV4-8.4-3B XC1

53 SOCKET 3 PIN 2.5mm XS3,XS4
54 SOCKET 6 PIN 2.5mm XS5

55

SOCKET FOR

EXTERNAL

CORDS

WP6-1B XL1

56 POLE SOCKET WP4-10A XC3

57

CONNECTION

CORDS

¦µ

0.6 SHAPED 7.5mm

W29,W32,W35,W36,W39,W48,W54,W58,W13

58

CONNECTION

CORDS

¦µ

0.6 SHAPED 10mm

W10~W12,W15,W19~W21,W27,W31,W33,W34,
W37,W43,W44,W47,W51,W53,W55

59

CONNECTION

CORDS

¦µ

0.6 SHAPED 12.5mm

W14,W16,W49,W50,W56

60

CONNECTION

CORDS

¦µ

0.6 SHAPED 15mm

W5,W7,W17,W18,W22,W23~W26,W28,W30,W45,W46
,
W40,W41,W52

61

CONNECTION

CORDS

¦µ

0.6 SHAPED 20mm

W38,W42,W57

62 FUSE TUBE T6.3AL 250V FL401,FL402

63

LARGE

RADIATOR

204×80×61 AB217 CONNECT TO THE MAIN AMP BOARD

64 FUSE HOLDER 0 FL401,FL402

65 SMALL CHIP AB207 FIX THE TRIODES V406 AND V416

66 TAPPING SCREW PB 3×12H COLOR ZINC 2 FOR SMALL CHIP AND LARGE RADIATOR

67 TAPPING SCREW PWT 3×8×8 COLOR ZINC 2 FOR PCB/RADIATOR

68

MACHINE

SCREW

PWM 3×16×8 COLOR ZINC 4 FOR POWER TUBE / LARGE RADIATOR

69 SCREW NUT M3 POWER TUBE SCREW

70 SCREW SPACER

¦µ

3×7.2×0.5

POWER TUBE SCREW

71 SPRING SPACER

¦µ

3

POWER TUBE SCREW

72 MICA SPACER 24×20×0.1 4 FOR POWER TUBE / LARGE RADIATOR

When this unit gets started, +5V is charged by C943 and adds an instantaneous high level
at the Port S. The Port R is grounded and is low level. According to the real value table, the
Port Q sends out high level and the Port Q' sends out low level. Although the Port S becomes
low level because C943 is full of charges, the Port D still keeps the original output modes for
it stays in low level caused by the connection between the Ports Q and Q'. The high level of
the Port Q of N908A is about 5V and reaches the inphase port of N910 through R1015.
However, the inphase opposition of N910A is about 1.6V. Thereby, the output port of N910A
sends out high level according to the voltage comparison characteristics. The level is sent
by R1016 to the display screen to lighten 2CH indicator. This unit switches to the 2CH mode
automatically when it gets started.

When pressing the switch S905, a triggered high level is sent to CLK. The output mode is
revered. Port Q becomes low level and Port Q' becomes high level. Because Port Q' is
connected to Port D, Port D also remains high level. Let go the switch S905, the input mode
remains due to the reaction of Port D. Because Port Q is low level, the positive voltage of the
inphase opposition of N910A will disappear. According to the voltage comparison characteri­stics, there's no high level sent out from the output port of N910A and thus the 2CH mode is
shut off. Meanwhile, the high level passes through R989 and reaches the inphase port of
N911A. The high level from the output of N911A is divided by R990 into two lines: One line
reaches the display screen to lighten the 5CH indicator. Another line reaches to the amplifi­cation circuit via VD916 to switch on the multi-channel output relay Y402. The channels C,
SR, SL are opened and there will be 5CH outputs. When pressing the switch S905, the output
mode is reversed once and returns to the 2CH mode.

6.2.2 The MIC delay selection section.

Its working principle is approximately the same to the channel selection. The difference is
that output Q and Q' will be divided into two lines: One line is sent to the voltage comparer.
Another line is sent to the Pins 4&6 of the echo processing IC N905 to control the delay time
of MIC signals in the echo circuit.

- 10 -- 17 -

6.3 The spectrum analysis section (Figure 9)

NO. DESCRIPTION

SPECIFICATIONS / PART

NUMBER

LOCATION SPECIFICATIONS

1

CARBON FILM

RESISTOR

1/4W680¦¸±5% SHAPED 10

R408,R424

2

CARBON FILM

RESISTOR

1/4W1K±5% SHAPED 10 R467-R474,R455,R456,R457,R458,R443,R406,R422

3

CARBON FILM

RESISTOR

1/4W3K±5% SHAPED 10 R411,R427

4

CARBON FILM

RESISTOR

1/4W3.3K±5% SHAPED 10 R453,R454

5

CARBON FILM

RESISTOR

1/4W3.9K±5% SHAPED 10 R433,R434,R436,R437

6

CARBON FILM

RESISTOR

1/4W4.7K±5% SHAPED 10 R403,R404,R419,R420

7

CARBON FILM

RESISTOR

1/4W10K±5% SHAPED 10 R405,R421,R445,R448,R444,R446,R441,R442

8

CARBON FILM

RESISTOR

1/4W22K±5% SHAPED 10 R402,R407,R413,R418,R423,R429

9

CARBON FILM

RESISTOR

1/4W47K±5% SHAPED 10 R462,R465,R466,R461

10

CARBON FILM

RESISTOR

1/4W1M¦¸±5% SHAPED 10

R447

11

CARBON FILM

RESISTOR

1/4W1.2K±5% SHAPED 10 R412,R428

12

CARBON FILM

RESISTOR

1/4W220¦¸±5% SHAPED 10

R401,R417

13

CARBON FILM

RESISTOR

1/4W150¦¸±5% SHAPED 10

R409,R410,R425,R426

14

CARBON FILM

RESISTOR

1/4W2.7K±5% SHAPED 10 R435,R438

15

CARBON FILM

RESISTOR

3W220¦¸±5% R-SHAPED 20×8

R451,R452

16

CARBON FILM

RESISTOR

1/2W220¦¸±5% SHAPED 12.5

R459,R460,R463,R464,R414,R430

17

CARBON FILM

RESISTOR

2W10¦¸±5£¥ R-SHAPED 20×8

R439,R440

18

CARBON FILM

RESISTOR

3W47¦¸±5£¥ R-SHAPED 20×8

R450

19

CEMENT

RESISTOR

3W0.25¦¸±5£¥ R-SHAPED 25×8

R415,R416,R431,R432

20

PORCELAIN

CAPACITOR

50V 10P ±10% NPO 2.5mm C433,C434

21

PORCELAIN

CAPACITOR

50V 33P ±10% NPO 5mm C404,C405,C409,C410

22

PORCELAIN

CAPACITOR

50V 271 ±5% NPO 5mm C402,C407

23

PORCELAIN

CAPACITOR

50V 102 ±10% 5mm C431,C432

24

TERYLENE

CAPACITOR

100V 104 ±10% 7mm C413,C414

25

TERYLENE

CAPACITOR

100V 224 ±10% 8mm C419,C420

26 CD CD11 16V10U±20%5×11 2 C401,C406,C443,C444

CD CD11 25V10U±20%5×11 2 C401,C406,C443,C444
27 CD CD11 16V47U±20%5×11 2 C425,C426,C429,C430
28 CD CD11 16V100U±20%6×12 2.5 C427,C428
29 CD CD11 25V47U±20%5×11 2 C403,C408

We have mentioned a LEVEL signal in Chapter 4 Volume, Tone and Balance Adjusting
Circuits. That signal is the spectrum analysis source. It was sent to 6-band spectrum level
display circuit composed of 6 voltage comparers: N911D, N911C, N911B, N912D, N912C
and N912B.

8 Detailed Circuit Explanations

8.1 The Power Amplifying Board

8.1.1 Main Parts List of The Matin Power Amplifying Board

The stronger the source

signal is and the more

the luminescent bands

there are, the higher the

indicated level.

LEVEL

The detailed working process: The inphase opposition voltages of these six voltage
comparers have their corresponding voltages respectively for the distributing resisters
are connected differently. We call these separate voltages valve voltages: N912Bca 0.2V,
N912Cca 0.4V, N912Dca 0.8V, N911Bca 1.6V, N911Cca 3.5V, N911Dca 5.2V. It's obvious
that their valve voltages increase by degrees. The LEVEL signal is coupled by R1010,
commutated and filtered by VD911 and C946. The output DC voltage is added at the inphase
port of these six voltage comparers. According to the voltage comparison characteristics,
when the source signal's voltage surpasses the valve voltage, the corresponding voltage
comparer's outputs will export high level to lighten the display screen's illuminant. For
instance, when input signal's voltage is 0.3V which exceeds the inphase opposition port's

0.2V valve voltage of the bottom N912B. Then the output of N912B exports high level to
lighten the bottommost illuminant on the display screen. On the other hand, 0.3V voltage
does not exceed the valve voltage of another five voltage comparers, so they will not export
high level. Neither the display screen can be lightened. When the input signal exceeds 5.3V
which is beyond the valve voltage of these six voltage comparers. Therefore, these six
voltage comparers' output ports will sent out high level and all six-band illuminants on the
display screen are lightened to achieve maximum display. Because the music signals are
changing continuously, these six illuminants will rise or fall accompanying with strong or
weak music signals. This is the basic working principle of the spectrum display circuit.

N911D

N911C

N911B

N912D

N912C

N912B

(Figure 9)

PL6

PL5

PL4

PL3

PL2

PL1

- 11 -

Illuminant

- 16 -

7.2.3 Short Circuit over-current Protection

7 Power Amplification and Protection Circuits

The channel R's output end is parallel connected with a over-current sampling triode V421.
R415 and R416 are over-current sampling resistor. When current soars up sharply due to
short circuit, the potential difference between R415 and R 416 also increases. The current
passes to the base and emitter of V421 through R433 and R434. When their potential differ­ence is beyond 0.7V, V421 is conducted and its collector's potential decreases. Finally, the
current passes VD405 and R443 to make V425 conducted and thus the relay is shut off.

Over

Current

Potential Difference

Between R415 and R416

Increases

V421

Conducted

V425

Conducted

Relay

Shut Off

7.3 Multi-channel Control Circuit

In the front panel circuit introductions, we have explained that when we choose the multi­channel output mode, N911A's output end sends out high level which reaches the base of
a compound tube composed of V434 and V435 through R441. V434 and V435 are
conducted and there is current in the coil Y402. Y402 is switched on. Channels C, SR and
SL pick up signals from channels R and L and then send them out.

The power amplification circuit is this unit's hard core which is working under high voltage
and large current volume, so its failure rate is very high. A protection circuit is added to the
power amplification's output to protect the amplifier and speakers' circuits. In addition, a
multi-channel switching circuit is also connected to the output of AB217. We take the R
channel as an ample to analyze the circuit as shown in the figure 10.

R

INPUT

AC Negative

Feedback R413,

R408,C403

Difference

Amplification

V401,V402

Mirror Image Constant

Current Source

V403,V405

VD401,VD402

Voltage

Amplification

V404

Compound Power

Amplification(NPN)

V430,V407,V409

Temperature

Compensation

V406

Compound Power

Amplification(PNP)

V431,V410,V408

Speakers

Protection

Circuit

- 15 -

Figure 10

- 12 -

7.1 Power amplification section

Over +4V V424 Conducted

Outp ut End

V425

Conducted

Relay Shut

Off

Below -4V V423 Conducted

7.2.1 Delay switch-on protection circuit

The R channel signals are coupled by R401 and C401 and sent to the base of difference
amplification section V401. V401 and V402 comprise the difference amplification circuit
of single input and output. The sound signal is sent from the collector of V401 to the base
of the voltage amplification section V404. The amplified signals reach the compound power
amplification section. V403, V405, VD401 and VD402 constitute the mirror image constant
circuit. VD401 and VD402 provide a constant base current to V403 and V405. The emitter
resistor of V403 determines the working current of the difference amplification section and
the V405's emitter resistor determines the working current of the voltage amplification section.
V430, V407 and V409 constitute the upper tube (NPN) of the compound power amplification
section. V430 and V407 are first parallel-connected to function as a triode (To raise the power)
and then compound V409 to constitute a NPN type compound tube (To make amplification
multiplied). V431, V408 and V410 constitute the bottom tube (PNP) of the compound power
amplification. Its circuit construction is the same as that of the upper tube except that it's PNP
typed after compounding. The temperature compensation section V406 has the following two
functions in the circuit: First, it is composed of the voltage reversed triodes of the same
parameters, so its working mode determines the static working current of the compound power
amplification section. That is to say, we can set up the static working point of compound power
amplification section through adjusting the V406 conducting level. The usual way is to change
the base resistor of V406. Second, it functions as automatically adjust the working mode of the
compound power amplification section when temperature rises. The adjusting process goes
as follows:

TOTAL OUTPUT CURRENT = WORKING CURRENT + LEAK CURRENT

When temperature rises, the leak current increases thus the total current increases (un­favorable condition). At the same time, the base current of V406 increases and Uce
decreases thus the output section's bias current decreases. Therefore, the working status
changes and the back working current decreases. The total current is limited in a certain range.

When this unit is getting started, +26V passes through R447 to charge C417. The positive
end voltage of C417 increases slowly. When the voltage supersedes 12V, VD409 (12V
voltage regulator diode) is penetrated and its negative end outputs high level which makes
the compound tube composed of V426 and V427 conductive. Therefore, their collectors'
potential is dragged down and there is current in the relay Y401. The relay is switched on.
The delay time depends on the constant of R447 and C417 charging time. The positive end
voltage of C417 is a key point through detecting which whether there is the voltage over +12V
to judge whether the whole protection circuit is started. When there is a voltage over +12V
and the relay is not switched on, it indicates that the problem only exists in the back compon­ents VD409, V426, V427 and Y401. When there is a voltage below +12 and the relay is
switched on, it indicates that the protection circuit is started and you need only to check the
corresponding circuits.

+26V

R447

charges

C417

Penetrates

VD409

V426 & V427

conducted

Y401

switched

on

7.2.2 Midpoint Over-voltage Circuit

A midpoint over-voltage sampling resistor R462 is connected to the output end of Channel
R (Channel L is R461). Because the power amplifying circuit is provided by twin power
supplies, the output end usually has two conditions: positive or negative voltage. They will
be analyzed respectively as follows. This protection circuit's protecting range is the voltage
above +4V or below 4V.

When the output end voltage surpasses +4V, the base receives a voltage above +0.7V
due to the voltage division by R462 and R445. V424 is conducted and the collector's
potential is dragged down.

7.2 Protection Circuit

The protection of the power amplifier's output section is performed by a relay series connect­ed between the output end and the speaker. The power amplifying circuit is not stable when
getting started and an impact current output will occur. If the output end has already been
connected to the speaker when getting started, BOO sound will come out of the speaker.
This is very harmful to the speaker. Therefore, we serial connect a relay between the output
end and speaker. In this way, when this unit is getting started, the relay is switched off and
the output end and the speaker will not be connected and thus the impact current will not
occur. The relay will open only when the circuit works stably. Therefore, the protection is
realized. In a similar way, when the circuit goes wrong and a high voltage and large current
will occur in the output end, the protection circuit will also cut off the relay to realize the
protection function. AB217 boasts its three protection functions: delay switch-on protection
circuit, midpoint over-voltage protection circuit and short circuit over-current protection
circuit. The working power of the protection circuit comes from a half-wave commutating
circuit composed of VD408 and C418. It's about +26V.

- 13 -

When the output end voltage is below 4V, the base of V423 receives a voltage below 0.7V
due to the voltage division by R462 and R445. V423 is conducted and the collector's
potential is dragged down..

According to the above statements, the collector's voltage will be dragged down whether
the output end potential is over +4V or below 4V. This low potential passes R444 and
makes the base's voltage of V425 decrease. V425 is conducted and thus its emitter's
voltage decreases. That is to say, the positive end voltage of C417 decreases and the
relay is shut off, thus the protection function starts.

- 14 -