SERVICE MANUAL AV210T SERVICE MANUAL

Chapter One Product Description

AV210T (RU) is an advanced power amplifier that has complete functions,

including 16 kinds of spectrum displays as well as tuning. This type of device can be
the best choice for those users who are fond of radios. Its main features are as follows:

1. Built-in 5-channel power amplifier that can adapt to AC-3, DTS and stereo
music playback. 35W main channel and 12W central surround sound.

2. AC-3, DTS, VCD and DVD. AUX input interface and subwoofer, stereo
output interface.

3. 6-channel volume control and independent level control. 7-band electronic
balance.

4. Bass enhancer system, cyber logic and hi-fi playback.

5. Multiple EQ modes that adapt to different music styles.

6. Automatic spectrum analysis and compensation, automatic signal
compensation.

7. Multiple frequency spectrum display modes.

8. Complete karaoke function including microphone independent volume control,
overall volume control, voice compensation, delay and echo.

9. Karaoke wide sound field function.

10. Tuning function.

11. Intelligent protection upon overcurrent and overvoltage.

1

AV210T (RU) Operating Principle Analysis

Section 1 Overall Structure

The device of AV210T (RU) can be divided into five constituent parts:

I. Power Supply:

Provide required working voltage to element circuits.
II. Signal Processing (including input, cyber logic, bass enhancer and volume control
circuit.)

Selecting input signal sources, cyber logic, bass enhancer, small signal

preamplification and independent electronic volume control over channels. “Bass

enhancer” function is added to AV210T (RU).

III. CPU Control

Being the control and processing center of the device, it consists of CPU, panel

control and software recognition circuit, providing users with a “man-machine

conversation” environment, so as to fulfill device control and frequency spectrum

display.

IV. Microphone Circuit

It consists of preamplifier circuit and echo processing circuit.

V. Power Amplifying and Circuit Protecting

Conduct post power amplification for small signal. Meanwhile, conduct

automatic protection for power amplifier circuit and sound box.

Ⅵ. Tuning
Mainly realize the reception and transition of radio signal.
Ⅶ. The principle figure of entire device is as follows:

F
更 改 数 量 更改单号 签 名 日 期

设 计 审 核

标 准 化

21

批 准

3

AV210TÔ-Àí¿òͼ

4

广东步步高电子工业有限公司

第 张

5

共 张 版次：

6

F

BBK

E

SW-out

VCD(L/R)

DVD(L/R)

5.1CH(L/R)

Tuner(L/R)

MIC1

MIC2

A

输入选择

BB

L/R

跟随缓冲

合成解码

L/R

数字调谐器

5.1CH(C/SL/SR)

5.1CH(SW)

DO/CL/DI/CE

OK

音量

VFD显示

DISPLY ÖжÏ

驱动电路

按键阵列

面 控 板

S-C

混合

D-SW
C/SL/SR
MIC

前置
放大

放大 检测

电源

灯丝/负压/+5V

遥控
接收

E

КдИлС¡Фс

D

A

SEL

电

C/SL/SR

程控
放大

检入
放大

±6.8V

D

电源

混合

提升

子

音

量

SW SW

ST1/DA1/CK1

MIC

带通
滤波

双限
比较

+6.8V
AGND

-6.8V

通道选择

SEL

S-C

D-SW

电子
混响

混响
调节

P_KT

+12V
AGND

-12V

MUT1

静音

C

SW

L/R L/R

MUT1

C/SL/SRC/SL/SRS-C/S-SL/S-SR

低通

+12V

电源

AGND

-12V

±6.8V

+5V

P_KM

通道

采样

切换

P_SELECT

P_SEARCH

检测

复位
电路

EEPROM

24C02

C

信 号 板 功 放 板

混合

混合

MIC

SW

Êä³öÇл»

±¬ÅïÇý¶¯ºÍÏß·

+6.8V
AGND

-6.8V
+5V

½ÓÊÕÍ·

P_REM

P_CHARGE

CPU

CPU板

B

静

音

B

Vc+

AGND

Vc-

功

率

放

大

过载
检测

保

护

电

路

L

R

C

SL

SR

¼МµзЖчЗэ¶¯

电 源 板

A

+12V

AGND

前置
电源

Vs+ GND Vs-

中环
电源

继
电
器

SW¾²ÒôºÍ¼ÌµçÆ÷״̬¼ì²â

主功放电源

A

1

-12V

2

3

L

R

4

C

SL

SR

5

6

2

更改：Amendment
数量: Quantity
更改单号：Amendment sheet No.
签名：Signature
日期：Date
设计：Designed by
审核：Examined and verified by
标准化：Standardization
AV210T 原理框图: AV210T principle figure
第 张: Page
共 张: Total pages
版次: Edition
广东步步高电子工业有限公司 BBK Electronics Corp., Ltd.
输入选择 Input selection
跟随缓冲 Follower buffer
合成解码 Cyber logic
通道选择 Channel selection
电子音量 Electronic volume
信号板 Signal panel
混合 Mixed
混合 Mixed
数字调谐器 Digital tuner
输入选择 Input selection
混合 Mixed
低通 Low pass
爆棚驱动和线路输出切换 Bass enhancer and circuit output switch
电源 Power supply
功放板 Amplification panel
静音 Mute
功率放大 Power amplification
前置电源 Front power
中环电源 Central surround power
过载检测 Overload detection
前置放大 Preamplification
放大 Amplification
检测 Detection
电子混响 Electronic echo
混响调节 Echo adjustment
提升 Promote
静音 Mute
接收头 Receiver
保护电路 Protection circuit
继电器 Delay
继电器驱动 Delay driver

3

SW 静音和继电器状态检测 SW mute and delay-status detection

主功放电源 Main amplification power supply
电源板 Power board
VFD 显示 VFD display
驱动电路 Drive circuit
电源 Power supply
灯丝/负压/+5V: Filament/Positive voltage/+5V
按键阵列 Button matrix
遥控接收 Remote control receiver
面控板 Control panel
程控放大 Process control amplification
带通滤波 Band pass filter
通道切换 Channel switch
采样 Sampling
中断 Cut off
检入放大 Input amplification
双限比较 Double comparison
检测 Detection
复位电路 Reset circuit
电源 Power supply
CPU 板 CPU panel

Section 2 Power Circuit

It provides required working voltages to element circuits. AV210T (RU) adapts a

loop transformer of 133W. The central and surround channels of AV210T (RU) adopt
dedicated power amplifier IC, and its left and right surround channels and central
channels adopt power amplifiers LM4731 and LM1875. And two channels of LM4731
use independent positive power supply to assure super separation between two
surround channels. Compared with the predecessors, it adds ±22V power supply as
well as standby function. The main purpose is to enter into standby without output of
main power amplifier by using CPU software program to cut off the relay in standby
mode. See the power supply and circuit diagram as follows:

Ⅰ. The DC power supply of ±36V is obtained via the rectification and filtration of
two sets of AC 26.5V outputted from the transformer at first sublevel by four IN5404s
and two big electrolytic capacitors (6800uF, 50V), providing power to left and right
channels.
Ⅱ. The power supply of ±22V is obtained via the rectification and filtration of two
sets of AC 16V voltages outputted from the transformer at second sublevel by four

4

IN5404s and two electrolytic capacitors (4700uF, 25V), providing power to SL, SR, C

r

r

y

p

channels, and also to other IC and operational amplifiers after voltage stabilizing via
voltage stabilizing tubes L7812 and L7912;

Provide PT6311 with drive power

Provide display with

filament voltage voltage

Provide main powe
amplifier circuit with powe
suppl

Provide SL/SR/C with

ower supply

Section 3 Input, Cyber Logic, Volume Control Circuit

The cyber logic function of AV210T（RU）is realized by C, SR, SL and SW channel signals
obtained after processing signals extracted on L, R channel by using low pass filter and band
pass filter. This circuit uses several electronic analogue switches to fulfill switching between
different modes (See Figure II for signal flow).

I. Input selection and mode switching circuit

AV210T（RU）has two sets of analogue audio source input modes and a set of 5.1 input
interface. The switching between them is releazed by using electronic switch. Two types of
electronic switch IC are used in the circuit: CD4052 (2-channel 4-option electronic analogue
switch) and CD4053 (3-channel 2-option electronic analogue switch). Their truth tables are
as follows:

5

CD4052 Truth

h

N

N

N

N

N

t

N

N

N

N

N

N

CD4053 Trut

X0 X1 X2 X3

0

A

B

1

0

0

XBY C

A

1

0

1

1

0

1

X0

X1 1

0

Y0

Y1

Z

Z0

0

Z1

1

In this circuit, there are another two important control signals, i.e. SEL and MUT1.
When SEL is of high level, the circuit is in external “5.1 channel” input mode; when SEL is
of low level, the circuit is in “cyber logic” mode; when MUT1 is of high level, “bass
enhancer” function will be enabled; when SEL and MUT1 are all of low level, the circuit is
in standard sound field processing mode. Here is a detailed analysis:

When pressing “input” button, PT6311 on the control panel will recognize the code and
send an execution request signal to CPU. Then the 32nd pin of CPU (N100) will return a data
signal to M62446. According to the “input” button status, the 1st, 2nd, 3rd, 4th pin of M62446
sends corresponding high, low levels, the combination of which will enable electronic switch
to circularly select between VCD→DVD→5.1CH→Radiohead. Now there are mainly two
statuses: two analogue input statuses (VCD, DVD) and 5.1CH input status. Their respective
signal flows are as follows:

1. 5.1 Input status: When A, B, SEL control lines of M62446 are of high level, L, R
channel signal of 5.1 input end is outputted from pin 3, 13 of N101 and sent to IC N106 for
functional adjustments of channel volume, sound field balance, etc.; meanwhile, the 4th pin of
N106 outputs a high level to pin 9, 10, 11 of electronic switch N102 (i.e. SEL control signal),

104B

VCD

5.1 inpu
L/R
channel

C/SR/SL
channel

5.1input
SW

6

N101

CD4052

input

selection

SL

SR

c

SW1

N102

CD4053

electronic

switch

104A

107B

N103

CD4053

electronic

switch

105B

SW

105A5.1 input

107A

to L/R

L

R

SW
C

SR

SL

15

M62446

electronic

13

volume

6

control

11

8

9

103B

SEARCH

106

108B

103A

100

CPU

（Fig. 2）