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...................................................
5.1 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 -
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