AKAI AV210, AV210 Service Manual

AV210

ENGLISH

SERVICE MANUAL

Echo IC Pt2399

CAUTIONS

CONTENTS

There is high voltage inside this unit. Make sure to pull out the plug of this unit before
repairing!
There are many high voltage components inside this unit. Please pay attention to all
warnings and instructions marked on this unit to avoid electric shock!
Specifications of the replaced components must be the same as that of the original
components. Do not change the components' specifications to prevent risks!

¢ñ

Cir cui t Makeup................................................................................................

Vol ume adj ust ment , sound f i el d pr ocess i ng and EQ adj ust ment ci r cui t s3. I nput si gnal s det ect , sear ch and f r equency s pect r um sampl i ng ci r cui t s. 4. Contr ol Ci r cui t .

1 INPUT PART.....................................................................................................2 ...................................................................................................................................5. Microphone Circuit............................................................................................6. Power Amplifi cation and Protection Circuit.........................................................

¢ò

.................................................................. I NSTRUCT I ONS TO THE CI RCUI TS

1. THE FRONT CONTROL PANEL.........................................................................2. THE MAIN AMP PART........................................................................................

¢ó

.................................................. THE E XPL ANATI ON FOR KEY COMPONENTS

CPU IC W78E54.............................................................................................. volume control IC M62446................................................................................ Echo lC Pt2399................................................................................................

1

1

3

3

4

8

10

12

12

16

24

24

25

27

- 27 -

¢ñ Ci r cui t Makeup

1. INPUT PART

AV210 has three ways of the analog audio source input and one group of 5.1 channel input
jacks. Their switch is realized by the electronic switch. The circuit incorporates two kinds of
electronic switch IC: CD4052 (dual channel one out of four electronic analog switch) and
Cd4053 (trio channel one out of two electronic analog switch). Their real value tables are as
follows:

CD4052 REAL VALUE TABLE

X0 X1 X2 X3

A

B

0

0

0

1

0

1

1

1

There are still two important control signals SEL and SEL1 in this circuit. When SEL is
high level, the circuit is in the mode of 5.1 CH input from outside. When SEL1 is high
level, the circuit is in the cyber logic mode. When both of them are low level, the circuit
is in the Hi-Fi mode (direct mode) and the standard sound field processing mode. They
work in the following steps.

the pins 38 and 39 of the CPU N422 are added into the pins 9 and 10 of the electronic
switch N401. The electronic switch selects the input mode circularly from VCD, CD,
AUX and 5.1CH according to different combinations of levels A and B. It can be divided
into two modes: 5.1CH and three analog input modes. Their signals' flow is as follows:

1.1 5.1CH input mode: In this mode, A and B are high levels, L and R channel signals
are sent out from the pins 3 & 13 of N401. Then the levels reach IC N402 to be master
volume adjusted after amplified by N407A and N407B. At the same time, the pin 32 of
CPU N422 sends out a high level to the electronic switch N410's pins 9, 10 and 11 (SEL
control signal). C, SR and SL signals are sent out from the N410's pins 14, 15 and 4
to IC N402 where separate volumes are adjusted. SW signals (D-SW) is sent to the IC
N402's where the volume is adjusted. Therefore, the 6 channel signals of 5.1 CH input
are selected by the electronic switch and added into the electronic volume adjusting IC
where the separate volume adjustment is performed. Then the signals pass to the rear
circuit, the whole unit's input source is selected as 5.1CH input mode.

1.2 Three analog input mode: Press the INPUT button to select one of the VCD, CD
and AUX. The select function is performed when the control levels Aand B from the pins
38&39 of the CPU N422 are added to the pins 9&10 of the electronic switch N401. The
signals of L& R channels are sent out from the pins 3&13 and then amplified in the oper
ational amplifier N407A and N407B. AV210 incorporates three processing modes to the
signals: Hi-Fi, Cyber Logic and standard stereo. Their signal's flow is as follows:

1.2.1 Standard Stereo Processing Mode: The L & R channel signals from the N407A
and N407B are added to the IC N402 where the electronic volume is adjusted. At the
same time, a signal selected from the L channel passes N408A and N406B where the
signal is processed through low pass filter to obtain a subwoofer signal (S-SW). S-SW
is added to N411's pin 5 and the pin 9 (SEL) is low level. According to the real value
table, S-SW signal is sent out from the pin 4 to N402's pin 6 where the electronic volume
is adjusted. In this mode, this unit is in the three channel output mode.

When pressing the INPUT button, the levelsA and B from

CD4053 REAL VALUE TABLE

X B Y C

A

0

X0

X1 1

1

Z

0

Y0

Y1

0

Z0

Z1

1

- 1 - - 26 -

1.2.1 Hi-Fi Processing Mode: The signal flow is the same as that of the standard stereo
mode. The electronic volume adjusting IC N402 shut off other audio channels under the
control of the CPU. Neither the sound fields processing and balance adjustment can be
performed. Therefore, S-SW cannot be sent out and the whole unit is in the two channel
output mode.

1.2.3 Cyber Logic: L&R channel signals sent out from N407A and N407B reach the IC
N402 where the electronic master volume is adjusted. Meanwhile, the signals selected
from the channel L passes through the low pass filter N408A where it is divided into two
lines. One line reaches the pin 13 of N411 through R657 and another line reaches the
pin 5 of N411 after it is amplified through the low pass filter N406B. The signal selected
from the channel R reaches the pin 1 of N411 after being amplified through the low pass
filter N408B. N411's pin 9 (SEL) is the low level. According to the real value table, the
S-SW signal sent out from the pin 4 is added to the pin 6 of N402 where the electronic
volume is adjusted. The pins 10&11 (SWLL) are high level. According to the real value
table, the central channel signal (S-C) sent out from the pin 14 of N411 and the surround
channel signal (S-S) sent out from the pin 15 of N411 are added to the pins 12, 2 and 5
of N410. (The S-S is divided into two signalssurround left and surround right.) At this
time, the pins 9, 10 and 11 (SEL) are low level. According to the real value table, these
three lines of signals sent out from the pins 14, 15 and 4 reach the IC N410 where the
volume is adjusted separately. This unit is in the six-channel output mode.

The relationship of all input source switches and sound processing mode is shown as
Figure 1.

volume control IC M62446

Press the INPUT

button to select

circularly

Three modes

input

5.1 CH input

Hi-Fi mode

Standard

Stereo

mode

Only L & R channel outputs,

Sound fields and

EQ settings are invalid

Only L,R & SW channel outputs,

Capable of setting the

Concert sound field and EQ

Cyber Logic

mode

(Figure 1)

6 CH output, capable of setting
the Theater sound field and EQ

6 CH output, capable of setting
the Theater sound field and EQ

- 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:

¢ó T HE E XP L ANA T I ON F OR KE Y COMP ONENT S

CPU I C W7 8 E5 4

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 -