Service Manual Ma-950s/850s 2004-10-03

Transcript

SERVICE MANUAL MA-950S/850S 2004-10-03 MA-950S/850S Principles and Maintenance 1. Product profile MA950S is a medium-grade active sound box consisting of five satellite sound boxes, i.e. one subwoofer sound box, two pre-positioned sound boxes, two surround sound boxes and one centrally-positioned sound box. The product features good sound effect in appropriate space, and it has the following features: 1) 2.1/5.1 sound channel output; 2) Tone and volume adjustment 3) Built-in five sound channel power amplification, and adaptable to AC-3/DTS and stereo music replay; 4) Six sound channel volume control and independent level control, with tone adjustment function. 2. Principle block diagram signal input Electronic volume and tone adjustment CPU system control Power amplific ation Remote Receiving display part Output and 3. System composition The device comprises input board, output board, power amplification board and control panel. The input board and output board only consist of a few terminals. The power amplification board is the most important part, fulfilling control, amplification and power supply for the whole system. In the following is the brief description of the principles for the power amplification board. 1) Power supply part In consideration of the big output power of the subwoofer, the device employs a ring transformer for power supply. A group of 18V(AC) voltages is output from the transformer, which will be subject to rectification and filtering and will output +22 V voltage to power IC TDA8947 and IC TFA9843 for power supply. One line of output 22V voltage goes through the current limiting resistor R101, voltage regulating diode VD104 and capacitor C108 and then output +9V voltage to IC 75347; the other line goes through R100 and voltage regulating diode VD105 and then output 5V voltage power supply for the CPU and the control panel. 2. Signal input, volume and tone adjustment The device has six channels for signal input. The signals input through each channel will go through the filtering capacitor before being directly delivered to the IC LC75347 for volume and tone adjustment. In addition, one line of signals will be derived from the L and R main sound channels and overlapped on the SW input. As a result, 2.1 output result will be achieved even when there are only L and R sound channel inputs. IC LC75347 is an IC with six-channel independent volume adjustment. With its gains adjustable from 0 to 95 single DB, it is applicable to home theater products. With benefits such as big range of power supply, low power consumption and wide temperature scope, it is a quite competent IC, and the functions of its main pins are listed in the following table: Pin name Pin Numbering Function description FLIN 7 Signal input FRIN 24 Signal input RL 20 Signal input RR 18 Signal input C 22 Signal input SBW 16 Signal input FLOUT 9 Signal input FROUT 10 Signal input COUT 11 Signal input RLOUT 12 Signal input RROUT 13 Signal input SBWOUT 14 Signal input VREF 23 Reference voltage VDD 37 Power voltage CE 40 Part signals selection control line DI 39 Data control line CL 38 Clock control line MUTE 35 External mute control The IC internal unit equivalent circuit: 3. Amplifying circuit part Principle: as far as the signals output from the IC 75347 are concerned, the signals of the main sound channel will be delivered to the N101 IC TFA9843 for power amplification; the central surround signals will be filtered and delivered to the N106 IC TDA8947 for amplification; the subwoofer signals will first pass experience amplitude limit (the amplitude limit circuit comprises VD110 and VD113 diodes) and pretreatment before being delivered to the N102 IC TFA9843. Amplitude limit is aimed at preventing excessive size of signals, which may, after amplification, damage the loudspeaker due to excessive power. Because the power supply of the amplification IC is fulfilled by a single power source, all amplified and output signals will have DC, therefore, the signals will still experience filtering before being output to the loudspeaker. IC TFA9843J is used for dual sound channel power amplification. With standby and mute modes, free from switch impact, and with functions such as short circuit protection and overheat protection, it can effectively be prevented from being damaged in case of IC abnormality. In ordinary output mode, the IC can supply for each channel a maximum of 20W power output. When BTL output is employed, the power can be as high as 40W. In addition, the IC features powerful anti-ripple performance, with little power consumption in the standby state. The functions of the various pins of the IC TFA9843J are listed in the following table: Symbol Pin Function IN2+ 1 2nd channel input OUT2- 2 2nd channel output CIV 3 Common mode input signal suppression 1N1+ 4 1st channel input GND 5 Ground SVR 6 Reference voltage MODE 7 Mode selection OUT1+ 8 1st channel output VCC 9 Power supply IC TDA8947J is used for four channel power amplification. Its features are similar to those of the IC TFA9843J, however, its output power is bigger, and a single sound channel can be as high as 25 W. 4. Control circuit MA-950S employs IC AT89C2051 to serve as its core part to control the operation of the whole device. With low voltage and high performance, it employs 8-bit 2K bytes flash and ROM single-chip. Boasting 15 I/O ports and six interrupt sources; it has features such as low power consumption and standby mode. The principle block diagram of the IC is illustrated in the following figure: Reset circuit: MA-950S employs high level for resetting. By making use of the feature of the capacitor C109 that there is no jump for of voltage, the device ensures that there is no jump of capacitor voltage at the instant of power on. The base electrode of the triode V100 has low level, so that the triode is not on, and the 5V voltage is added to the first pin of the CMP through resistor R114. With capacitor charging, the positive voltage of the capacitor gradually climbs; when the voltage attains a certain limit, the voltage regulating diode is reversely on, so that the base electrode of the triode has high level, the triode is on; the reset pin voltage turns into low level, thus fulfilling resetting. The circuit diagram is illustrated in the following figure: Reset circuit Mainly remote control is employed for adjustment of the status of the device. The signals received by the remote controller are delivered to the sixth pin of the CPU. After the signals are processed inside the CPU, pins 7，8 and 9 deliver control signals to adjust the volume of the device. Then there will be corresponding display on the control panel through P1 port, so that users are able to understand the status of the device. In addition, pins 2 and 3 of the CPU are used to control the mute state of the main sound channel and the central surround. 5. Control panel The control panel of the device consists of a remote control receiver and a nixie tube. Because the device is operated through remote control, the remote control receiver is the sole path for man-machine communication. The nixie tube is used to display the ongoing operation and the state of the whole system. 6. Power on/off mute and mute circuit Power on/off mute: as shown in the figure, at the instant of power on, the voltages on both sides of capacitor C169 won’t experience jump-off, as a result, the low level will remain unchanged, the triode V106 is off, V105 is on, MUTE1 output turns into low level, LRM and SCM signal levels turn lower, and then there is mute. When the capacitor is charged to turn on VD109 5.1V voltage regulator tube and V104 9014 triode, the level of the V105 base electrode will become lower, so that triode V105 turns off, MUTE1 outputs high level, and the mute then comes to an end. The same case applies to power off. Capacitor C169 experiences fast discharge through diode VD112, so that the positive voltage experiences fast decrease, triode V106 turns off, V105 turns on, MUTE outputs low level and turns on. It is through this circuit that we achieve no impact sound when power is on/off. Mute circuit: the mute function is realized through the mute signals transmitted by the CPU. Press the MUTE key on the remote controller, the remote control receiver will receive signals and transmitted them to the CPU for processing. Then, pins 2 and 3 of the CPU will transmit high level, so that triodes V107 and V108 turn on, LRM and SCM levels become lower, and the mute is on. It makes use of the mode selection feature of the IC TFA9843 and IC TDA8947. For more details, please refer to the information for the IC TFA9843. 4. Troubleshooting The electronic circuit inside the device is relatively simple, without too many complicated control and detection circuits. As a result, signal injection method is employed for the maintenance of the device, namely, signals are added to the input end, and flow along the signal procedure. If signals are interrupted at a certain place, then we can determine that the fault may happen here. The maintenance of the device is in compliance with the following procedures: 1. Check whether the power supply part is normal; namely, check whether the power supply of 22V, 9V and 5V is normal; 2. In case of abnormal sound but normal power supply, check whether the mute level is normal, and then consider whether it is attributed to the wrongness of other parts; 3. For a device with abnormal display, first determine whether there is anything wrong with the nixie tube, and then check whether there is anything wrong with the CPU. ******************ATTACHMENT*************************** 1: Block diagram 2: Electronic diagram 3: PCB silk screen 4: IC specifications OUTPUT BOARD MAIN BOARD L R R 5.1CH INPUT VOL C SL SR L R C¡¢SR¡¢SL CONTROL CONNECTED BLOCK SL POWER AMP SW SL Coupling Capacitor POWER AMP L SW R L¡¢R INPUT BOARD C L SR C LPF SR AMP SW ground POWER AMP CPU MUTE CONTROL SW BTL LED REMOTE RECEIVER PANEL BOARD POWER connected DISPLAY SUPPLY R100 VD100 XS100 2 1 C187 103 CON2 1N5404 +22V VD101 1N5404 C100 VD102 1N5404 +5V 270/3W R101 270/1W 4700u/35V FL100 T6.3AL 250V R129 +9V +5V C101 104/100V VD104 C102 C103 VD105 C108 9.1V 220u 5.1V 100u 473 C104 18K VD103 1N5404 22K R138 47K R106 2.7K/0.25W C168 R167 10K R140 C188 22u/50V 103 270 V105 S8050 VD109 5.1V X103 FL101 C126 2 1 R178 R115 4.7K 4.7K C124 C123 G100 5 4M C125 6 7 4.7u/50V 9 1 2 C186 102 C185 102 C184 102 L100 472 C183 100 10 100 100 1 2 22K P_LRM 44 43 42 41 40 39 38 37 36 35 34 22K R125 4.7K R110 22K R124 4.7K R109 22K R126 4.7K R113 22K SL 10u/16V C116 SR 10u/16V C117 OUT2 OUT3 OUT4 VSS CE DI CL VDD TIM MUTE FLT RLO RRO SBWO NC SBW NC RR NC RL NC C 4.7K LC75347E FRT TRE2 BASS23 BASS22 BASS23 FL NC FR SELR FRIN VREF 33 32 31 30 29 28 27 26 25 24 23 C C181 C180 473 C113 473 10u/16V C114 SR C118 10u/16V C127 P1.0(AIN0) C164 V111 9014C V112 9014C P_LRM R171 V109 2N5401 0 C130 C165 IC4558 +9V 12 R120 4.7K V104 9015 GND CON12 9015 11 10U/16V C138 472 100K 5 C132 R148 100K R152 100K 150K 0.1u 182 N105B 7 IC4558 C136 1u R146 10K 4.7K R176 0.1u C135 0.1u 1K C150 C142 472 LRM 22K 22u S8050 C137 C145 C163 22u/16V C149 VD115 0.47u 100u/25V TFA9843J OUT/SL 1 2 3 4 5 6 7 8 9 SL OUT+ OUT4+ GND1 VCC2 VCC1 GND2 OUT2OUT3MODE2 CIV IN2+ IN4+ SGND SVR IN1+ MODE1 IN3+ 17 16 15 14 13 12 11 10 OUT/C +22V C174 C144 VD107 C106 473 100u/35V C148 1u/16V 100u/25V 1N4148 TDA8947J OUT/SR C R158 47u/35V TFA9843J 100u/35V N106 10K 473 VCC OUT1+ MODE SVR GND IN1+ CIV OUT2IN2+ C105 473 C147 MUTE1 1N4148 SR OUT/R N102 9 8 7 6 5 4 3 2 1 +22V VCC OUT1+ MODE SVR GND IN1+ CIV OUT2IN2+ R174 9014 0.1u +22V VD108 1N4148 100K L C173 C140 472 1K R144 1K R143 R 22u/25V 104 C139 472 R172 100K V110 C143 C146 OUT/L R145 R112 100K 9 8 7 6 5 4 3 2 1 VD106 1N4148 C170 472 R111 C120 OUT/R 10K N101 C133 CUT R179 R173 LRM 100u/25V C107 6 MUTE1 0.1u C134 1K R166 100K 223 1 4.7K V108 C152 R155 10u/16V C151 2 13 R118 V103 9015 C129 Vr 3 4.7K P_SCAN VD114 R139 10u/16V C119 1u/16V R156 VD110 47K N105A 4.7K 14 R119 P_SCM SW 103 R154 Vr (T1)P3.5 15 R117 V102 9015 +5V RE R175 1K CUT R181 4.7K R147 100K 10u/16V C121 R153 1N4148 1N4148 47K C167 10u/16V P1.1(AIN1) V101 SL C122 22u/16V R177 4.7K 100K (T0)P3.4 10u/16V C115 VD113 R164 R168 100K R C179 1U/50V C 100K C166 P1.2 10u/16V SW R163 103 P1.3 (INT1)P3.3 16 R142 L 10u/16V 10u/16V (INT0)P3.2 1 2 3 4 5 6 7 8 9 10 11 12 330 330 330 330 17 GND AT89C2051 P3.7 CUT R180 4.7K 682 C182 12 13 14 15 16 17 18 19 20 21 22 R123 R108 10u/16V C112 OUT1 TRE1 BASS11 BASS12 BASS13 SELL FLIN NC FLOUT FROUT COUT P1.4 1K R141 4 22K R 8 R105 1 2 C177 473 3 4 C176 473 5 6 1U/50V 7 8 C175 9 10 11 10u/16V C111 R149 100K CON7 L R SL GND SR C SW 4.7K R150 100K 7 6 5 4 3 2 1 22K R122 R151 100K MA-850S/MA-950S MAIN BOARD XS106 R104 C178 682 L P1.5 XTAL1 1N4148 N103 C110 P1.6 XTAL2 18 V107 9014 C131 104 CON2 4.7K P1.7 (TXD)P3.1 R134 R133 R135 R136 19 +9V L 333 X102 R121 20 Vcc (RXD)P3.0 4 30P 10 XS105 RST/Vpp 3 4.7u/50V R116 4.7K 1 8 R127 R130 R131 CON2 103 R132 N100 30P 9014C 1u/16V C109 +5V P_SCM V100 C172 CON2 T2AL 250V X101 V106 R165 47K C169 R102 22K P_LRM 2 9014 +22V 1N4148 3.3V VD116 +5V VD112 R107 MUTE1 VD111 1N4004 4.7K 10K R170 R114 4.7K R103 473 R128 10K 10K R169 OUT/L R157 1/1W C154 220u/25V 1 2 CON2 R160 C156 OUT/SR 220u/25V 1/0.5W OUT/C C157 220u/25V 104 C158 104 C159 104 C161 104 C162 104 1/0.5W 1/0.5W XS104 C160 1/0.5W R159 C155 220u/25V OUT/SL C128 104 C153 220u/25V R161 R162 1/0.5W XS107 1 2 3 4 5 6 7 CON7 R L SL SR C GND