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Principle, Knowledge and Maintenance of
AV230 (RU)
Contents
Chapter One Product Description
Chapter Two Operating Principle
Section One Structure
Section Two Volume Board
Section Three Signal Processing Board
Section Four CPU Board
Section Five Control Panel
Section Six Voice Board
Section Seven Power Panel
Section Eight Power Amplifier Board and Protection Circuit
Chapter Three Maintenance Process
Chapter One Product Description
AV230 (RU) is an intelligent premium power amplifier that adds touch button
and voice navigation to its predecessor, allowing it to have a handsome and
distinguished appearance as well as a complete man- machine interaction mode that
facilitates user operation. Its main characteristics are as follows:
1. Built- in 5-channel power amplifier that can adapt to AC-3/DTS and stereo
music playback. 110W main channel and central surround sound.
2. Mix of AC-3/DTS, VCD and DVD. AUX input interface and super
bass/stereo output interface.
3. 6-channel volume control and independent level control. 7-stage electronic
balance.
4. Bass enhancer system, cyber logic, hi- fi playback.
5. One button for movie, music and karaoke.
6. Intelligent voice navigation.
7. Multiple electronic balance modes that adapt to different music styles.
8. Automatic spectrum analysis and compensation, automatic signal
compensation.
9. Profile surround sound. Situation effect processing for AC-3/DTS effect.
10. Multiple spectrum display modes.
11. Complete karaoke function including microphone independent volume
control, overall volume control, and voice compensation, delay and echo adjustment.
12. Karaoke wide sound field function.
13. Touch control function.
14. Intelligent protection upon overcurrent and over voltage.
Chapter Two Operating Principle
Section One Structure
AV230 (RU) mainly consists of the following seven parts:
I. Volume Board: select input of signal source, cyber logic, and bass enhancer control.
II. Signal Processing Board: karaoke signal processing and 5.1-channel signal
amplification.
III. CPU Board: overall control, frequency point gating, automatic search circuit.
IV. Control Panel: VFD display, touch selection and backlight display.
V. Voice Board: intelligent voice navigation system, operating mode indicated by voice
VI. Power Panel and Protection Circuit: provide operating voltage required by element
circuits and execute overall protection.
VII. Power Amplifier Board: power amplification of 5.1 channel signal or analog signal.
Section Two Volume Board
AV230(RU) has four input modes: AUX., VCD, DVD and 5.1 channel.
The cyber logic function of AV230 (RU) is to get C/SR/SL/SW channel signals by
sampling from L/R channel and then processing through low-pass filter and adder
subtractor. Mode switch is achieved using electronic analog switch. The signal flow chart is
as follows:
AUX
CD4052 L
VCD R
electron OUT
DVD
5£®
1CH ic
N104B
switch
N107B N104A N106
N105B M62446
N101
N105A
N107A
SWIN
S-C
C CD
S-SR
4053
SR
electr
S-SL onic
SL
switc
CD N108B
S-C
4053 DISPLY
electr
SW
onic
switc
h
I. Input option and sound field processing mode
The input option of AV230 (RU) is achieved via electronic switches CD4052 and
CD4053, the truth tables of which are as follows:
5.1 channel input mode: Now A/B/5.1CH control pins of M62446 are of high level.
L/R channel signal of 5.1 input is outputted from pin 3/13 of N101 and sent to IC N106 for
volume and tone control; meanwhile, C/SR/SL signal on 5.1 input terminal is respectively
sent from pin 14/15/4 output of N410 to IC N106 for independent volume control. And SW
signal is outputted via pin 4 of N103 and then send to M62446 after being amplified by
N107A.
Three analog input modes: AV230 (RU) totally has three analog input modes:
AUX/VCD/DVD, which are controlled via A/B signal respectively (see details in truth
tables).
AV230 (RU) totally has three sound field modes: standard sound field, cyber logic and
Hi-Fi.
1. Standard sound field: Under overall CPU control, when bass enhancer is off, L/R
channel output and subwoofer output are available; when bass enhancer is on, only L/R
channel output is available.
2. Hi- fi: Under overall CPU control, only L/R channel output is available to M62446;
3. Cyber logic:
Pin 9/10 of electronic switch N101 (CD4052) select a series of analog L/R channel input
signals. N101 (CD4052) signals. L/R signals are outputted from pin 13/3 via the internal
electronic switch of N101, and divided into two ways. One way is respectively sent into pin
13/15 of M62446, for electronic volume and tone control. The other way produces
SW/S-SR/S-SL/S-C signals via buffer, adder-subtractor and low-pass filter. SW/S-SR/S-SL
signals are sent to pin 12/2/5 of N102. N102 select synthesis and decoding signal input (see
truth table of CD4053) from synthesis and decoding and 5.1CH signals, outputs C/SR/SL
signals and sends into pin 11/8/9 of M62446 for volume control. Still another way of SW
Hi-fi L/R channel output
mode only. Sound filed and
Two Standard L/R/SW output only.
analog sound Concert hall sound filed
and balance setting
Press "input" Cyber 6-channel output.
key to select logic Theater sound filed and
5.1 input 6-channel output.
mode Theater sound filed and
signal directly sends to pin 6 of M62446 after being outputted from N107A. 5.1CH signal
sent into M62446 is outputted from pin 31-36 after volume and tone control, and then
outputted to signal board by XS20 power distributor.
The relation between sound sources in input circuit and sound processing modes is as
illustrated below.
II. Control circuit
Pin 23/26/27 of CPU (N100) output data, PVST and clock signal and send to pin
39/40/41 of M62446, controlling pin 1/2/3/4 of M62446 to output control level, so as to
select input signal and spectrum sampling signal. It is worth noting that PVST signal is a
latch control signal. When the data and clock of CPU is sent to M62446, an identification
signal will be added, indicating that this signal can only be used by M62446 while other IC
of I2 C bus can not use current data and clock signal.
III. Frequency spectrum sampling circuit
Only S-C/S-SR/S-SL/SW signals are sampled during frequency spectrum sampling in
AV230£¨ RU£© added to pin 14 via a 150K sampling resistance. Another S-C synthesis
and
and decoding signal is added to pin 1 of N103, called S-C£§ 5.1CH and LR-T of
.
M62446select sampling signals. When synthesis and decoding is selected, the control
signal of 5.1CH is of low level while pin 9/11 of N103 is of low level. According to the
truth table, it is known that the outputs are X0/Z0. Sampling signal is grounded while LR-T
is of H level. Select Y1, S-C£§ signal is outputted from pin 15 of N103 to N108B, adding to
OK-R signal for the amplification of frequency spectrum signal, and then sent to frequency
point gating and auto search circuits.
Section Three Signal Processing Board
The signal processing board superposes, mix and amplify 5.1-channel signal sent from the
volume board, voice signal sent from the voice board and karaoke signal.
I AV230£¨ RU£© Karaoke Circuit
1. Function: this circuit process human voice through power amplifier and reproduce it
via speaker. It includes human voice beautification circuit, wide sound field processing
circuit, karaoke echo and delay regulating circuit. In addition, AV230 (RU) has a special
circuit that enables 5 profiles without inserting microphone.
2. IC and its role for karaoke
IC serial Name of IC Role of IC
number
N201 4558 Transmittal. Preamplification for karaoke signal
N200 PT2315 Volume control of karaoke, including tone control
N205 CD4053 Electronic switch
N209 PT2399 Karaoke echo processing
N207 CD4051 Karaoke delay adjustment
N208 CD4051 Karaoke echo control
N204 4558 Phase inverter
PT2315 function pin
S/N Name of pin Description Remarks
1 REF Reference voltage (1/2VDD)
2 VDD Power supply
3 AGND Analog
4 TREB L
L/R channel treble control pins
5 TREB R
6 RIN R channel input
7 LOUD-R R channel loudness control pin
9 LOUD- L L channel loudness control pin
11 LIN L channel input
12 BIN L L channel bass control input/output
13 BOUT L pin
14 BIN R R channel bass control input/output
15 BOUT R pin
16 RFOUT R channel output
17 LFOUT L channel output
18 DGND Digital
19 DATA £¨ DATA£© control data of sequence
transmission (DATA)
20 LCK Clock input of sequence
transmission
8£¬
10 NC Not connected
3. Flow chart of karaoke signal
MIC
N205
N200 N202B N203B N209
N201 N204
pass
N202A N207
N100
Karaoke
N208
V200 mixed
CPU
When the microphone is inserted, MIC signal is sent via MIC to the transmittal circuit
combined by N201A and N201B for amplification. Amplified MIC signal gives CPU a
MIC identification signal after N202A amplification, followed by VD201 rectification and
filtering control triode V200. CPU sends PKM signal, which is of low level, causing cutoff
of triode V103/V105 and enabling output of MIC signal; another way reaches pin 6/11 of
PT2315 after C219/C222 coupling, outputs from pin 16/17 after internal volume and tone
control, mixed into one way and sent to N202B and then reversely send to N203B for
amplification. Signals amplified by N203B are divided into two ways. One way is directly
outputted. The other way is outputted from pin 14 after being coupled by R222/C247 to
PT2399 for internal delayed reverberation adjustment, reversed by N204 and outputted by
mixing with karaoke signal. While OK-R is outputted from pin 14 after being gated by
N205 and superposed to L/R channel.
In this circuit, the bass boost network made up of triode V201 connected to the
negative terminal of N202B is primarily for bass boost of 75HZ low frequency signal.
During delay adjustment for PT2399, first control signal is given to CPU, which sends
this control signal to N100 by data communication with voice processing IC
(N100HT86P00, HT86384) , and then N100 will control N207 to connect to pin 6 of
PT2399 by selecting different resistance values for purpose of delay adjustment.
Echo control is to change the resistance value at the connection point to R229, so as to
change the superposition on through connect signal for echo control.
The wide sound field processing control signal of SOK' karaoke is in wide sound
s
field mode when it is of high level, when the signal of OK-R is the OK signal inverted by
N204A.
A sense signal of OK-SW on the MIC plug conducts MIC signal detection together
with the network made up of V200. When MIC is not plugged, it is of low signal; when
plugged, it is of high signal.
Karaoke auto mute is also available. When P-KT fails to detect signal for a continuous
time, CPU will send a P-KM signal to mute karaoke and avoid MIC from receiving noise,
which may affect sound effect.
l Signal flow chart of profiles
AV230 (RU) has a special function that switching between 5 profiles is available
without karaoke. Its flow chart is as follows:
N204
A
N209
N205 N203B
N204
B
N207
Mixed output
N208
HT86P00
When pin 9/10 are of high level, sampled L/R/C signals are outputted via from pin 3
N205 gating, and sent to the internal of PT2399 after amplification by N203B for
reverberation delay adjustment (by HT86P00 and HT86384 for voice processing), and then
superposed to L/R/C channel to form different profiles.
In this circuit, MIC shall not be inserted and is only available in 5.1CH mode. N203A
is for the purpose of reversal.
II. Bass enhancer circuit
P-BURST is the switch signal of bass enhancer. When it is of high level and added to
the base electrode of V102, V102 will be switched into conduction. When the collector
electrode outputs low level, V107 will be cut off; when the collector electrode is of low
level, V107 will also be cut off. SW signal is normally outputted to external terminal.
Meanwhile, the high level signal of P-BURST is added to the emitter electrode of V108.
V108 is positively biased and switched into conduction. The collector electrode adds high
level to the base electrode of V101. V101 is positively biased and switched into conduction,
and ground SW signal, not superposing it to L/R channel signal.
In reverse, when P-BURST is of high level, V100 will be switched into conduction
and SWM signal cannot be outputted from external terminal. Meanwhile, V101 is cut off
and SW signal is superposed to L/R channel signal.
The bass enhancer of AV230 (RU) can be divided into three steps. This principle is to
change the volume of bass enhancer by changing the SW output volume of M62446.
Meanwhile, SWM signal is added to relay via XS9. When the relay is off, SW signal
will be grounded, disabling the output at super bass port.
III. Mixing and amplification circuit of 5.1 signal and karaoke
After L/R channel signal of 5.1 signal is superposed with SW signal and amplified by
N101B/N100B, it is sent to the reverse phases of N101A/N100A. Meanwhile, OK-R/OK-L
signals are also respectively added to the reverse phases of N101A/N100A. After mixing
and amplification by N101A/N100A, they are outputted respectively from pin 1 of
N100A/N101A to power amplification circuit for power amplification.
Meanwhile, the C-1 signal sent by volume board is added to the reverse phase of pin 6
of N102B and added to the reverse phase of N102A after amplification. Now C1-1 signal
after electronic reverberation processing is also added to the reverse phase of N102A and
sent to power amplification circuit after mixing and amplification.
SR-1/SL-1 of another volume board is also added to the reverse phases of N103B and
N104B for amplification and then sent to N103A and N104A for further amplification, and
later sent to power amplification circuit.
One way of 5.1 signal being mixed and amplified is sent to power amplification circuit
passing through XS9, and the other way forms DIST (distortion error detecting signal)
signal passing through R111-R113/R142/R145/VD100-VD104, which will be added to
CPU for automatic gain, so as to control volume output.
IV. Voice channel test circuit
CD4051 Truth
X0 X1 X2 X3 X4 X5 X6 X7
A 0 1 0 1 0 1 0 1
B 0 0 1 1 0 0 1 1
C 0 0 0 0 1 1 1
N105 is a single pass 8-option electronic switch, 5 ports of which are used. The voice
signal of voice board sent by C127 and R155 to the reverse phase of NN108A for
amplification, and then added to pin 3 of N105. The output terminal is changed by high/low
control level of pin 9/10/11 (see the truth table above), enabling it to respectively add to the
reverse phase of N100A/N101AN/102A/N103A/N104A as required by CPU, for mixing
and amplification with 5.1 signal, so that speakers can produce corresponding sounds when
being tested and thus determining if each speaker is normal.
Section 4 CPU Board
Achieve overall control, automatically search input signal and analyze spectrum
CPU Overall Control
N100, the overall CPU, is the overall control center, inputting all kinds of
control instructions to controlled circuits to achieve all kinds of control
functions. It adopts +5V supply with pin 40 as its supply pin. Pin 18 and pin
19 connect externally with 12M crystal oscillator to provide working clock
frequency for itself. Pin 9 is its reset pin. When starting, +5V charges C106
via R100. The voltage of two ends of capacitance cannot be mutated, thus
B-pole of triode V100 is low level, that is, V100 conduction gives a high-level
reset signal to CPU. When capacitance C106 finishes charge, V100 stops and
then reset finishes. The form of this reset circuit is to reset high level and keep
low level.
When the machine is working, the static information of start log in the
screen and Chinese characters are stored in CPU internal static memory. N101,
a status memory, can record the current working status of machine when
cutting off and show the status when next starting up, avoiding users to
re-adjust. The sound mode set by users is also stored in it and can be activated
when necessary.
Detect Input Signal and Automatically Search Circuits
DISPLAY signal from volume board is sent to N103A to amplify and
limit level, and then sent to inverse end of voltage comparator N103B after
capacitance coupling. It inputs from pin 7 of N103B and then is sent to pin 16
of CPU via VD103, V101, R109 and R107. When N103B inputs a high level,
VD103 is in reverse cut-off status, B-pole of switch tube V101 is high level
and is in conducting status, then gets an about +5V high level (signal input) to
CPU after VD101' stabilization and stop searching. When the output end of
s
N103B outputs a low level, VD103 is in conducting status, B-pole of
switching tube V101 is low level and is in cut-off status, and then CPU detects
the low level (no signal input). Its working principles are:
¢ÙAfter starting up, under CPU internal program' control, a data signal
s
is outputted via pin 23 to M62446, and then M62446 scans each input port of
N101, N102 and N103 by emitting high and low levels. When the input ports
have no signal input, it automatically becomes standby status. When any of
ports has signal input, track paths of input N101, N102 and N103 has A/C
signal which is amplified and limited level by N108B and N103A of CPU
board, then compares with pin 5 of N103B and gets plus-minus level close to
supply power. The cophase voltage of N103B is about 0.1V. After the direct
current voltage is over 0.1V, the output end of N103B outputs low level is
close to negative-power voltage, VD103 positive-bias conducts, switch tube
V101 (S9014) stops, emitter outputs a low level to pin 16 of CPU which by
controlling IC M62446 makes search level lock on the port through which
signal inputs, to enter normal play.
¢ÚWhen pressing "search"key of remote controller, it is converted from
optical signal to electric signal by the remote receiving head of panel. Pin 14
of CPU emits a high level to conduct V102 and search according to the same
previous process.
Spectrum Analysis Circuit (See Following Diagram)
There are three parts for spectrum analysis circuit:
Seven-segment
band-pass filter
N105C 35HZ
N108
DISPLAY +
. 134HZ
300HZ
CD4051 }
N104 3 -
1KHZ CPU
CD4051
2.2KHZ Frequenc
Gain
y-point
adjustme 6.3KHZ
gating 3
nt of auto
} 16KHZ
spectrum
CPU
N102A
-
V105 Pin 12 of CPU
N102B
+
¡£
+5V V103 . V104 Pin 28 of
A/D conversion
1¡¢
Automatic spectrum gain adjustment circuit: to avoid two situations
that spectrum display amplitude is too low when input signal is too weak
or spectrum display is in full screen when input signal is too strong,
AV230 (RU) sets automatic spectrum gain adjustment circuit, using a
single-channel one-from-eight electronic analog switch, its true value
diagram is as following:
CD4051Truth Value List
X0 X1 X2 X3 X4 X5 X6 X7
A 0 1 0 1 0 1 0 1
B 0 0 1 1 0 0 1 1
C 0 0 0 0 1 1 1 1
Its main working principle is to change the value of inverse ground resistance
of transmittal N104 to change the transmittal gain multiple. Let' see the
s
detailed work of the whole circuit. We' referred that spectrum analysis
ve
signal source (display) is sent to the cophase input end of transmittal N105C
to amplify. Its amplification factor is determined by the value of the resistance
connecting with the electronic switch of its inverse end N104. When the main
volume is large, CPU will automatically increase the value of ground
resistance and decrease the amplification factor; when the main volume is
small, CPU will automatically decrease the value of ground resistance and
increase the amplification factor.
2¡¢
Frequency-point gating circuit: signal amplified by N105C is sent via
C115 coupling to seven band-pass filters composed of transmittals. By
setting its capacity of feedback capacitance, its frequency-band range can
be determined. The frequency value of superscript of the output points is
the central frequency-point of the frequency band. The output end of each
band-pass filter is connected with a half-wave rectifier circuit. The
amplified A/C signal is rectified to direct current. The circuit is mainly to
achieve frequency-point sample. It can display the amplitude of all
frequency-points of the whole sound signal via direct-current voltage. If
the low frequency of sound signal is stronger, the current voltage of output
end of 35HZ and 100HZ band-pass filter is higher. When high frequency
is stronger, the current voltage of 10K and 16K band-pass filter is higher.
The output ends of the seven band-pass filter are connected with the seven
input ends of electronic switch N108 (CD4051). These electronic switches
will quickly circularly-switch among frequency points (refer to previous
true value diagram). Pin 3 output end of N108 will output a string voltage
value representing frequency point signal amplitude (see next diagram).
V Note: the voltage
amplitude in diagram
1KHZ
100HZ 10KHZ
35HZ 300HZ 16KHZ
3KHZ 35HZ
T
Interval of switch
Frequency-point circle
3¡¢ conversion and output circuit display (two situations):
A/D
1¡¢When no signal input, pin 28 of CPU sends a high level to B-pole of
V104. The positive end of N102B is low voltage, the inverse end of N102B
gets partial voltage of R189 and R172, making N102B output a low level, that
is, triode V105 stops and C-pole of V105 will give a high level to pin 12 of
CPU to let CPU not conduct AD conversion (pin 6/7/8 of CPU are inactive
and keep high level).
V V
Discharge of
100HZ
35HZ
35HZ 100HZ
T
T
Diagram6
Interval of Charge Charge
2¡¢
When the machine has detected the signal (the inverse end of N102B
has a current voltage representing 35HZ signal amplitude), pin 28 of CPU is
converted into low level and +5V voltage charges for C137 via V103. When
reaching the voltage value of inverse end, the comparator converts and N102B
outputs high level. Once CPU receives low-level signal, it stops 35HZ level
gating and converts into next frequency point 100HZ. During conversion, pin
28 of CPU outputs an instant high level to conduct V104, leak the voltage
capacity of C137 and make the cophase end of N102B restart to charge
100HZ from 0-level. When the charge of 100HZ finishes, the charge and
discharge of next frequency point begin, and such process occurs circularly
under the control of CPU. The charge time form 0-level to the occurrence of
output conversion represents the signal amplitude of current frequency
point-- the larger the amplitude, the longer the time and the amplitude
displaying in screen is higher; the smaller the amplitude, the shorter the time
and the amplitude displaying in screen is lower. Digital pulse outputted from
N102B output end is added by V105' inverse to pin 12 of CPU which handle
s
it and output to panel to display dynamic frequency in screen. The display of
original frequency points is sequential. However, the above circular process is
extremely quick, thus, what we see in screen is the progress of the whole
spectrum displaying synchronously.
Chapter 5 Control Panel
The panel control circuit is the window for man-machine interaction. It
can communicate the operation command with CPU to finish kinds of
artificial operations. At the same time, it is the window of the complete
machine by which human can predominate the complete machine' working
s
status. It is also the important element to its appearance. The AV230£¨
RU£©
panel control circuit block diagram are showed as follows:
VFD display
Drive circuit Power supply Step up circuit
Button LED backlight
display
CPU Remote-control receive
Power supply circuit
1. The AV230£¨
RU£©
control panel have +5V£¬
-30V£¬¡« power
2.8V
supply¡£he circuit consists of VD109£¬D110£¬D102£¬D103£¬
T V V V
V107 and V108¡£
Operating principal£º
After the AC current from the transformer was rectified and
filtered by VD109 and VD110£¬ series regulated power supply
the
made up of V107 and V108 supply +5V for the next. With the VD102
for rectification and VD103 for stabilized voltage at the same time,
the 30V for display driving was supplied to 16311. In addition,
another ~2.8v was delivery to display filament to make VFD filament
brighten.
Circuit for VFD display drive and push button
The circuit consists of N101, N102, touchscreen and VFD. The tact
switch of touchscreen was made of glass which the backlight can
transmit through to play the role of ornament.
Operating principal£º
When displaying, the 16311 receive the signal for displaying from CPU
through VFD communication port, and make the corresponding VFD
field point lighten by internal processing. If there is any push button be
operated, corresponding signal would be output to CPU through the
inner push button matrix code of 16311.
Step up circuit and backlight circuit
This circuit consists of N104MP8004 step up IC, step-up coil, V104,
V105 control triode and backlight.
Operating principal£º control the first pin and the third pin of IC8004,
By
system controls the PWM signal of inner IC, then control V104 and
V105 to make the step-up coil store energy and step up, and supply the
backlight for lighten ulterioriy.
Section 6: Speech Board
AV230 (RU) amplifier circuit, comparing with previous amplifiers, has
a greatest feature of adding a speech navigation system, making the whole
machine more intelligent and humanistic.
Ò»¡¢
Block Diagram
¡¢
Speech
P-LDA LPF Amp
processing
lify
P-LHOLD
When CPU receives the instruction, it immediately communicates with
speech processing chip N100 (HT86384) to send the instruction to N100. The
speech chip connects with EPROM. The speech is stored in the EPROM and
after internal processing, couples via C127 from pin 30 output analog audio
signal to low-pass filter circuit composed of N108A, then after filtering noise,
couples by C126 to pin 2 of N106 (HT82V733) for power amplification and
the amplified signal outputs from pin 1 and pin 7 ends to push the loudspeaker
to emit speech signal.
CPU takes communications by P-LBCK, P-LDA and P-LHOLD.
¶þ¡¢
Working Conditions of HT86384
Pin 33 and 34 are clock pins, adopting 8MHZ working clock. Pin 27 and
28 are supply pins. Pin 22/23/24 respectively takes communications with
P-LBCK, P-LDA, P-LHOLD and CPU. Pin 31 is reset-input pin, keeping high
level for the resetting of low level (V100 with R103, R105 and R106 together
forms reset circuit).
HT86384 is bonding IC. If the IC is damaged, please change the whole
bonding board.
Èý¡¢
Functions of HT82V733 Pin
Pin 1 2 3 4 5 6 7 8
Output Input External Ground Enable Null Output Power
Function Negative filter control pin positive supply
capacitor end
Note: pin 5 is enable control end. It is normally working when high l vel and
e
forbidden to run when low level. By using it, the function of speech switch
may be achieved.
Section 6 Power Board
It is used for providing all kinds of needed working voltage for units of
the whole machine. AV230 (RU) adopts a ring transformer with 335W power.
The middle and surround track of AV230 (RU) respectively adopt LM1875
and LM1876. LM1876, the dual-track power amplification IC, supplies power
by separate positive power, ensuring there is high separating degree between
two surrounds. It adds +VSS supply comparing with previous machines. The
diagram of power supply circuit is as following:
Ò»¡¢
Two A/C 38V of transformer first level output is rectified and
filtered by four IN5404 and two big electrolytic capacitors
(15000uF/68V) and gets plus-minus 53V power to supply for right
and left sound tracks.
¶þ¡¢
Two A/C 21V voltage of transformer second level output is
rectified and filtered by four IN5404 and two electrolytic
capacitors (4700uF/35V) and gets plus-minus 28V power to
supply for SL/SR/C sound tracks. Other IC and operational
amplifiers are stabilized by stabilizing tube L7812 and L7912 and
gets power to supply for other IC.
Panel
¡«
26V display
Filame
¡«
2.2V
¡«
220V50HZ
nt
Rectifier
Power
¡«
38.5V filter
amplifier
of L and
Power
amplifier
¡«
16.3V Rectifier
stage of
filter
C,SL
Power-amplification Board and Protective Circuit
Ò»¡¢ amplification circuit of L and R sound tracks: L and R main power
Power
amplification circuits of AV230 (RU) are composed of separate elements. The
block diagram is as following (taking L sound track for example)
¸ ´ º Ï ¹ ¦ Â Ê · Å ´ ó
A/C negative V132£¬
V112
feedback
L
Differential
amplificatio
Voltage
amplifi
cation
. Temperature
compensatio
Sp
V101 n stage ea
Re
V115 ker
lay
Mute
Compound power
Image constant-current
amplification
source
L-track signal is sent by coupling of R101, R103 and C101 to B-pole of
differential amplification stage V102. V102 and V103 compose of differential
amplification circuit of single-end input and output. Speech signal is outputted
from C-pole of V102 to B-pole of voltage amplification stage V105, and then
to compound power amplification stage after amplifying voltage. V104, V107,
VD102 and VD103 compose of image constant-current source circuit. VD102
and VD103 provide constant base current for V104 and V107. The emitter
resistance of V104 decides the working current of differential amplification
stage and the emitter resistance of V107 decides the working current of
voltage amplification stage. V132 and V112 compose of compound tube
amplification, making the final stage of power amplification with strong
current amplification, which compose of wave plus half-circle amplification.
V133 and V113 compose of wave minus half-circle amplification, whose
circuit structure is completely same to the previous tube. Two functions of
temperature compensation tube V106 are: firstly, it is the base-level bias of
upper and lower tubes. Its working status determines the static working
current of compound power amplification. That is, we can set the static
working point of compound power amplification stage by adjusting V106
conduction. The common way is to change the base resistance of V107. It can
also automatically adjust the working status of compound power amplification
stage when the temperature arises. The adjusting process is:
Total current of output stage = working current + leakage current
When temperature arises, leakage current also arises, causing the static
working point flow (bad). At the same time, the leakage current of V106
arises and Uce decreases, causing the bias current of output stage decreases,
working status changes and working current of back pole decreases, in order
to compensate temperature.
Voltage negative feedback is introduced in power amplification circuit of
AV230 (RU), composing of R121, R109 and C105, stabilizing the static
working point of differential stage. AV230 (RU) adopts direct output. R111
and C116 of its output end compose of Rubeier network, preventing
high-frequency self-excitation caused by A/C inductive reactance of
loudspeaker speech coil.
The principle of R-track is same to that of L-track. No more words
here.
Èý¡¢
Mute circuit: when pressing mute key of remote controller, a
photoelectric conversion mute signal by remote receiving head is sent
to CPU, whose pin 35 and 36 emit a high-level mute instruction to
conduct V115, V101 and V116 and L and R-track signal short pass
ground, achieving the mute control.
ËÄ¡¢ SR and SL power amplification circuit: comparing with previous
C,
machines, these three tracks of AV230 (RU) adopts special power
amplification LM1876 and IC LM1875. LM1876 has 15 pins. The pin 2, 15
and 4 are respectively its plus-minus power pin. The pin 7/8/12/13 is its
cophase and inverse input end. The rated output power of each track of the
power IC can reach 20W with automatic mute function when starting up. 1875,
five pins, is a power amplification IC with better performance and extremely
simple application circuit which has 15W power output in rated status. Its pin
5 and 3 is plus-minus power supply pin.
Îå¡¢
Protective circuit
The protective way of L, R and C tracks is to cut off relay Y100 when
starting up to cut off its output. SR and SL tracks protect by mute. AV230
(RU) has functions of starting delay protection, mid-point over-voltage
and over-current protection and standby protection.
4¡¢
Starting delay response protective circuit: because the circuit is unstable
when starting up and its dash current does great harm to sound box and
power amplification circuit, the delay response protective circuit is set.
There are two steps for starting delay response protective circuit: firstly, C,
L and R. Its working process is: the A/C of transformer is rectified and
filtered by VD113 and C110 to form a 22V voltage, then R108 charges
C115 to inversely breakdown VD111 and V105 and V104 forward
conduct, finally the Y100 responses and delay forms. Secondly, L and R
surround tracks take starting anti-dash protection by following ways:
when the system resets, pin 33 of CPU outputs a high level, passing R164
to pin 9 and 14 of LM1876 which outputs mute. After machine successes
in delay starting, pin 33 of CPU switches into low level and SL/SR path
normally outputs.
5¡¢
Mid-point over-voltage protection: the output end of each track is
connected with a over-voltage sampling resistance. L-track is R116,
R-track is R117, C is R118 and SR and SL are respectively R119 and
R120. As long as any mid-point voltage of tracks is over +3.5V or lower
than -3.5V, V101 or V102 conducts to decrease their C-pole voltage, then
V103 conducts to finally cut off relay to protect circuit starting.
over+3.5V V101
Each track is L CH is conducts C-pole Cut off relay
V103
connected R voltage to protect
condu
with an Less than +3.5V V102 decrease circuit
over-voltage conducts
6¡¢
Over-current and short-circuit protection: output load resistances of L and
R-track are connected with an over-current sampling triode. The sampling
tube of L-track is V114 and load resistance is R126 and R127. The power
amplification IC of other three tracks has functions of over-current
protection. As long as over-current occurs in L-track, the voltage drop of
R126 and R127 will rapidly increase. Once the voltage drop of R129 is
over 0.7V, V114 will conducts, and then V103 conducts and finally relay
cuts off to protect circuit starting.
Each track is The voltage
L track V114 C-pole Cut off relay
V103
connected drop of R126
is V114 cond voltage to protect
condu
with an and R127
decrease circuit
over-current
In same manner, voltage of R159 will be over 0.7V to conduct V129, then
conduct V103 and finally cut off relay to protect loudspeaker.
7¡¢
Energy-saving protection: when standby time reaches 10 minutes and still
needs continuing, CPU pin 34 output PRC signal is high level which
saturates and conducts V100 via VD108 and R101, then conducts V103
and finally cuts off relay to save standby energy.
Maintenance and repair flow
Malfunction Phenomenon£ºSound fault
Analysis£º
Generally, such fault can be checked by signal injection step by
step. If the speaker of any step has no disturbance, there must be problems
with this step. In general, this method should be carried out from rear step to
front step. Another method is signal detection, which is carried out from front
step to rear step. If there be no sound with any step, this step must be the fault
point. Specific examine and repair flow for this fault is showed as follows:
No microphone
No
Check C219£¬
C222 to confirm Check circuit for N210 and
if there be sound or not microphone
Yes
No
Check R219 and R220 to Check PKCK, PKDA signal of
confirm if there be sound or not PT2315 and CPU
Yes
Check R230 to confirm if No Check N202 and its power
there be sound or not supply circuit
Yes
No
Check C245 and C246 to Check N203 and its power
confirm there be sound or not supply circuit
Yes
No Check if V104 or V105 have
Base electrode of V104 and
been broken-down or not
V105 is 0.7AV or not?
Yes
No
The E-electrode of V103 is V103 fault
high level or not?
Yes
MICDET be high level?
No CPU fault
PKT be low level?
Microphone fault
V200 fault
Fault phenomenon: No display
No display
If there be any change between high level Y Check CPU and
and low level on collect electrode of V105 I2 C bus
N
V105 itself and its power supply is N Check power supply, V105 and
normal or not? peripheral circuit
OK
VD118 is normal or not? N Replace
VD118
OK
N Check the circuits with
N102B forward terminal
V103 and V104
voltage jump or not?
OK
N102B reversal has high level N Check N102 and
and low level or not? peripheral circuit
OK
N
N108 and CPU control pin work Check control signal, N108
properly or not? and peripheral circuit
OK
Check the auto-gain regulate circuit made of seven-segment
band-pass filter, C115 and N105
Èý¡¢ phenomenon£º
Fault Automatic search fault
Automatic search
fault
N
DISPLAY signal be delivered to Check spectrum sampling and
103A reversal or not? amplifying circuit, N103 and N108B
Y
N
Check N103A amplifying
Voltage be supplied to N103B
circuit and power supply circuit
reversal or not?
Y
Cophased terminals of N103B N Check N102 and
be low level or not? peripheral circuit
Y
VD103 be normal or not? N Replace VD103
Y
Check VD101, CPU, V101 and
peripheral circuit
ËÄ¡¢
Starting up protection
Check if there be Mid-Point Voltage or not?
Y Check which sound channel output DC
and check this sound channel
N
Check if signal or main volume should be
augmented for protection
Y Check if overcurrent protect diode or triode
be damaged, or capacitor C115 is poor
N
Check if resistance R111 and R141
be open circuit
N Y Replace resistance
Check if resistance R108 be
open circuit
N Y Replace resistance
Check if RLY inspecting signal work
properly
Check if resistance R201 be open
N Y circuit on CPU board
Vibration protection or not? Y
Replace relay