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MA-700
Service manual
MA-700 Principle and Servicing
1. Unit circuit principle
MA700 is a middle-level active speaker, which is composed of a subwoofer speaker, two front
satellite speakers, two surround speakers and a centre speaker and with excellent sound effect. It has
the following features:
¡ô2.1/5.1CH output;
¡ôBuilt-in 5CH power amplifying, adaptable to AC-3/DTS and stereo music replay;
¡ôWith 6CH volume control and separate level control, and with tone adjustment function.
(1) PCB board composition figure of the player
The player includes input board, output board, power amplifier board and control panel, in which,
input board and output board are comprised of several terminals; the main part is power amplifier board,
control, amplifying part of the player and power supply are all included on it. PCB board composition
figure of the player is shown as the following figure 1.1.1:
CIRCUIT CONNECTION DIAGRAM
1.~14V
2. 0 XS1
3.~14V
POWER AMPLIFYING BOARD OUTPUT BOARD
1. GND 1. GND
2. GND 2. GND
3. C 3. C
INPUT BOARD XS4 4. SR 4. SR XP4
1. L 1. L
1. SW 1. SW 2. R 2. R
2. SR 2. SR 3. SL 3. SL
3. SL 3. SL
XP2 4. C 4. C XS2
1. R 1. R
2. L 2. L XS3
3.GND 3. GND SW SPEAKER
XP3
SW
FRONT PANEL'S BOARD
Figure 1.1.1 PCB board composition figure of the player
-1-
(2) Principle block diagram of the player
The principle block diagram of the player is shown as in the following figure 1.2.1: signals arrive at
electronic volume and tone adjustment circuit through input terminal for tone and volume adjustment,
and then are sent to power amplifying circuit for amplifying output. The information receiving and
sending of CPU control the working state of the player and drive display circuit to display.
Electronic
volume
Signal Power
& Output
input amplifying
tone
adjustment
CPU Receiving, display part
Figure 1.2.1 Principle block diagram of the player
(3£©
Signal block diagram of the player
Signal block diagram of the player is shown as in the following figure 1.3.1:
L
BLOCK DIAGRAM
MAIN POWER AMPLIFYING BOARD R
L R SL SR SL
INPUT BOARD
POWER
AMPLIFICATION
SR
L
L R SL SR
R
C
C
5.1CH VOLUME C
C
SW CONTROL
INPUT POWER
L R SW AMPLIFICATION
SL
SR
LPF
SW
AMPLIFICATION
SW
POWER
AMPLIFICATION
OUTPUT BOARD
CPU
LED
REMOTE
CONTROL
RECEPTION
POWER
SUPPLY
DISPLAY
FRONT PANEL'S CONTROL BOARD
Figure 1.3.1 Signal block diagram of the player
-2-
(4) Power supply circuit
Because of the output power amplifying of subwoofer, this player adopts round transformer to
supply power to the machine. A group of 18V voltage is outputted from transformer, after rectification
filtering, +22V voltage is outputted to supply power for power IC TDA8947 and IC TDA9843.
One path of the outputted 22V voltage, through current limiting resistor R101, voltage regulating
diode VD104 and capacitor C108, outputs +9V voltage to supply for IC TDA7448; the other path,
through R100 and voltage regulating diode VD105, outputs 5V voltage to supply power for CPU and
control panel.
(5) Signal input and volume, tone adjustment circuit
This player has 6-channel signal input; the signal inputted in each channel, through filtering
capacitor, is directly sent to IC TDA7448 for volume and tone adjustment. In addition, one signal is
pulled to L and R main channel individually and overlapped to SW input, thus, when there is only L, R
channel input, 2.1 output effect may also be achieved.
IC TDA7448 is a IC with separate 6-channel volume and tone adjustment function, and its gain is
adjustable by 095DB, which is adaptable to home theatre series products. It has strong points of large
power supply range, small power consumption and wide applicable temperature range and is a good
performance IC.
(6) Amplifying circuit
Signal outputs after adjustment of TDA7448, in which main channel signal is sent to N101 IC
TDA9843 for power amplifying, but centre/surround signal is sent to N106 IC TDA8947 for amplifying
after filtering; subwoofer signal, firstly through dipping (clipping circuit is composed of diode Vd110 and
Vd113), then through pre-processing and then is sent to N102 IC TDA9843. The function of dipping is to
prevent the loudspeaker from being burnt down because of too large power of signal after being
amplified. Amplifying IC is supplied power by single power, so the amplifying outputted signal is with DC
and filtering is needed before outputting to loudspeaker.
IC TDA9843J is a dual-channel power amplifying IC with standby and mute mode, without power
on/off percussion and with functions of short-circuit and over-heat protection, which may be used to
effectively prevent IC being damaged in abnormal conditions. This IC may provide max 20W power
output for each channel in common output mode. When BTL output is adopted, power may be up to 40W,
in addition this IC is with powerful anti-ripple function and power is very small in standby state. ¡£
IC TDA8947J is a 4-channel power amplifying IC and its main features are similar to IC TDA9843J,
but the power that can output is large, and single channel may be up to 25W.
-3-
(7) Control circuit
CPU of this player adopts IC AT89C2051 to control the working of the whole machine. 6CH volume
adjustment, channel level adjustment, mute control, digital display and remote control function
realization are all controlled through CPU. This IC is a low voltage and high performance IC, which is a
single chip which adopts CMOS technique and flash with 2K byte and readable storage, it has 15 I/O
ports and 6 interrupt sources, and with low power consumption and standby mode.
(8) Reset circuit
This player adopts high level reset and utilizes the feature that voltage of capacitor C109 cannot
jump. At the moment of power on, capacitor voltage cannot jump, base electrode of triode V100 is low
level, triode is not on, and 5V voltahe is added to pin 1 of CPU through resistor R114. For capacitor
charge and voltage of anode of capacitor increases gradually, when voltage is up to a certain degree,
voltage regulating diode is reversely on to make base electrode of triode high level, triode is on, voltage
of reset pin changes into low level and reset finishes, shown as in the figure 1.8.1:
+5V
R103 R114
18K 4.7K
VD116 3.3V
V100
9014
R102 C109
22K
4.7u/50V
Figure 1.8.1 Reset circuit diagram
(9) Remote control circuit
The state of this player is adjusted mainly by remote control. Signal received through remote control
is sent to pin 6 of CPU, through CPU internal processing, sends out control signal to adjust the volume
and tone of the player through pin 8, 9 and controls panel display through P1 port to make users know
which state the machine is in. In addition, main channel and centre/surround mute is controlled through
pin 2, 3 of CPU.
(10) Control panel circuit
Control panel of this player is composed by a remote control receiver and a digital tube. This player
is operated through remote control, so remote control receiver is the unique route for man-machine
conversation. Digital tube displays the operation being performed and state of the player.
-4-
(11) Power on/off mute and mute circuit
Power on/off mute: shown as in the figure 1.11.1, at the moment of power on, voltage of two ends of
capacitor C169 cannot jump, so low level is kept not to change to make triode V106 cut off and V105 on
to make MUTE1 output low level to pull down LRM and SCM signal level to cause mute. When capacitor
is charged to make VD109 5.1V voltage regulating pipe and V104 9014 on, base electrode level of V105
is pulled down to make triode V105 cut off, MUTE1 outputs high level and mute finishes. It is the same
with that when in power off. Capacitor C169 discharges quickly through diode Vd112 to make its positive
voltage decrease quickly to make triode V106 cut off, V105 on, MUTE output low level and mute is
opened. That no percussion sound appears when power on and off is realized through this circuit.
VD112 1N4148 +22V
R138 R167
R107 100K 47K 10K
C168 R140
4.7u/50V R106
4.7K/0.25W 270
C172
V105 4.7u/50V
VD109 S8050
5.1V
C169 R165 9014C
10u/25V 47K V106
Figure 1.11.1 Power on/off mute circuit diagram
Mute circuit: the mute function of this player is realized through the mute signal sent out by CPU.
When pressing MUTE on remote controller, remote control connects to CPU and send out high level
from pin 2, 3 of CPU to make V107, V108 on, LRM signal is pulled down to 15V from 22V, LRM signal is
sent to pin ODE of TFA9843, mute of TFA9843 opens. For TDA8947 mode selection function, please
refer to IC TDA9843 materials for details.
2. Troubleshooting
Electronic line inside this machine is simple without complicated control, detect circuits, so signal
injection is adopted for this machine's servicing, that is, signal is added to signal input end and then
follows signal flow. If signal interrupts suddenly in a certain place, and the trouble lies in this place
basically. Therefore, for servicing of this machine, do according to the following process:
(1) Check whether power supply part is normal, that is, check whether power supply of 22V, 9V and
5V is normal;
(2) For abnormalities, such as there is no sound, in conditions of normal power, you should check
whether mute level is normal, then consider whether other elements are abnormal;
(3) For machine with abnormal display, firstly make sure whether digital tube is abnormal, then
check whether CPU is abnormal.
-5-
3. Troubleshooting process
(1) Troubleshooting process for " output"is shown as in the following figure 3.1.1:
No
No output
Check N
whether power supply Check and repair voltage part
is normal
Y
Check N
Check each polar tube of
whether mute is normal
mute circuit
Y
Change N103
Figure 3.1.1 Troubleshooting flow chart for " output"
No
-6-
(2) Troubleshooting process for " OSD"is shown as in the following figure 3.2.1:
No
No OSD
Check N
whether output is Refer to troubleshooting
normal process for " output"
No
Y
Check
whether U101, N
U102, U103, U104 are Change
normal
Y
Change digital tube
Figure 3.2.1 Troubleshooting flow chart for " OSD"
No
-7-
(3) Troubleshooting process for "Power not on"is shown as in the following figure 3.3.1:
Power not on
Check N
whether protector tube Change transformer
is burnt down
Y
Check
whether power is short N
Change protector tube
circuited to
ground
Y
Check whether power IC is burnt down
Figure 3.3.1 Troubleshooting flow chart for "Power not on"
-8-
4¡¢
Function Introduction to IC
(1)function introduction to TFA9843J
1)Description
The TFA9843J contains two identical audio power amplifiers. The TFA9843J can be
used as two Single-Ended (SE) channels with a fixed gain of 26 dB or one Bridge-Tied
Load (BTL) channel with a fixed gain of 32 dB.
The TFA9843J comes in a 9-pin DIL-bent-SIL (DBS) power package. The TFA9843J is
pin compatible with the TFA9842J and TFA9841J.
The TFA9843J contains a unique protection circuit that is solely based on multiple
temperature measurements inside the chip. This gives maximum output power for all
supply voltages and load conditions and no unnecessary audio holes. Almost any supply
voltage and load impedance combination can be made as long as thermal boundary
conditions (number of channels used, external heatsink and ambient temperature) allow it.
2)Features
n SE: 1 W to 20 W; BTL: 4 W to 40 W operation possibility
n Soft clipping
n Standby and mute mode
n No on/off switching plops
n Low standby current
n High supply voltage ripple rejection
n Outputs short-circuit protected to ground, supply and across the load
n Thermally protected
n Pin compatible with the TFA9842J and TFA9841J.
3)Pin description
Pin Symbol I/O Description
1 IN2+ I Input 2
2 O OUT2- O Inverted loudspeaker terminal 2
3 CIV O Common input voltage decoupling
4 IN1+ I Input 1
5 GND I Ground
6 SVR I Half supply voltage decoupling (ripple rejection)
7 MODE I mode selection input (standby, mute and operating)
8 OUT1+ O non inverted loudspeaker terminal 1
9 VCC I supply voltage
- 9 -
(2)function introduction to TDA8947J
1)Description
The TDA8947J contains four identical audio power amplifiers. The TDA8947J can be used as: four
Single-Ended (SE) channels with a fixed gain of 26 dB, two times Bridge-Tied Load (BTL) channels with a
fixed gain of 32 dB or two times SE channels (26 dB gain) plus one BTL channel (32 dB gain) operating as a
2.1 system.
The TDA8947J comes in a 17-pin Dil-Bent-Sil (DBS) power package. The TDA8947J is pin
compatible with the TDA8944AJ and TDA8946AJ.
The TDA8947J contains a unique protection circuit that is solely based on multiple
temperature measurements inside the chip. This gives maximum output power for all
supply voltages and load conditions with no unnecessary audio holes. Almost any supply
voltage and load impedance combination can be made as long as thermal boundary
conditions (number of channels used, external heatsink and ambient temperature) allow it.
2)Features
n SE: 1 W to 25 W, BTL: 4 W to 50 W operation possibility (2.1 system)
n Soft clipping
n Standby and mute mode
n No on/off switching plops
n Low standby current
n High supply voltage ripple rejection
n Outputs short-circuit protected to ground, supply and across the load
n Thermally protected
n Pin compatible with TDA8944AJ and TDA8946AJ.
3)Pin description
Pin Symbol I/O Description
1 OUT1+ O Non-inverted loudspeaker output of channel 1
2 GND I Ground of channels 1 and 2
3 VCC1 I Supply voltage channels 1 and 2
4 OUT2- O Inverted loudspeaker output of channel 1
5 MODE2 I Mode selection 2 input: mute and on for channels 3 and 4
6 IN2+ I Non-inverting input2
7 SGND I Signal ground
8 IN1+ I Non-inverting input1
9 IN3+ I Non-inverting input3
- 10 -
Pin Symbol I/O Description
10 MODE1 I Mode selection 2 input: mute and on for channels 1 and 2
11 SVR I Half supply voltage decoupling (ripple rejection)
12 IN4+ I Non-inverting input4
13 CIV I Common input voltage decoupling
14 OUT3- O Inverted loudspeaker output of channel 1
15 GND2 I Ground of channels 3 and 4
16 VCC2 I Supply voltage channels 3 and 4
17 OUT4+ O Non-inverted loudspeaker output of channel 1
- 11 -
5. audio power amplifying PCB board
C126 SWITCH ~18V XS100 GND C SRSLL R R158
XS107
C127
4MA700-0
R155 VD110
VD113
C164
R159
2004 04 02
R154
C160
C162 R162C161 R161
C158
FL100T6.3AL250V
R164
XS102
FL101 T2AL250V C166
R149
C110
R153
101
N105
R163
XS
C153 R177
R160 C159
C118
W37
C165 C167 R150
R120
R152
R127
C152 R156
C122
JP103
VD102
VD103
C121
W1 XS103
VD104 C151 C111 R151
C157
R137
R131 C103
XS105
V104 C156 C155 C154 C119 C114
R116 VD101 C112
R118
R114 R138 C102
R108
R105
R104
R130 V106 C116
JP102
C101
R103
R111
R148
W31
C142
VD116 R101 C172
N100 R115 W20 V105
V103 R174 R167 C113 C115 C117 R110
R102 W6
JP101 R140 C120
R141
V102 VD100 W19 VD115 R109
R100
R168
C169
R113
R139
R176
R145
C133 R165
VD109
R126
R125
R123
R122
R119
R124
R121
R142
R106
R166
V100 C109
JP100R117 C124 W21
C125 VD112
R112
C138
R147
G100 W35 R107 V108
VD105
V101
W38
C168
R136 W12 VD111
W34
C139
C140
R135 C123
C170
W32
R133 W5
C100
R134
W15
SW C SR G SL R L
R129
R128
C104
C108
VD114
W36
W26
W14
W39
W22
XS106
W11
R170 V107
W29
W8
R132 R169
W27
R175
W18
W28
W16
W17
W23
W24
W9
C131
W7
C163
C148
C174
C144
C106
W10
C143
W25
R171
C149
C173
W13
W3
XS104 R173
W30
C145 C130 V109 W33
C128
C129 C146
C135
C150
C107
C137 R146
VD107
W4
R172
SW C147
VD108 V110 VD106
C175
W2
SW C105
R157
C136
C134
C132
JP104 L/R
R143 S/C N101
N102 R144 N106
- 12 -
6. circuit diagram
(1)KEY SCAN Board
N100
3
VS
1 DS100
OUT
2 DPY
GND
a
REMOT 1 f b 8
2 g 7
3 e c 6
C100
4 d 5
105 [LEDgn]
- 13 -
DPY-7
R109 1
10
11
12
1
2
3
4
5
6
7
8
9
XS100
CON11
GND
VCC
RE
P_SCAN
(2)IN OUT Board
1
L
2 XC100A
AV6
3
R
XP100
L
1 R 4
2 SL L XC100B
3
GND 5
4 SR
5 AV6
C 6
6 SW R
7
CON7
7
L XC100C
8
9 AV6
R
XC100A
1
R100
220/0.5W
2
WP10
XC100B
- 14 -
3
R101
220/0.5W
4
WP10
XC100C
5
R104
220/0.5W
XP100 6
R
7
L WP10
6
SL XC100D
5
SR 7
4 R102
C
3
GND 220/0.5W
2
GND 8
1
CON7 WP10
XC100E
9
R103
220/0.5W
10
WP10
(3)audio power amplifying board
R128 4.7K
P_LRM
+5V