Akai AA-A25/Y1 User manual

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· COMPUTER CONTROLLED s·tEREO RECEIVER
-.
. ·, ,, '
. AA~A25/v1
MODEL AA-A2 5L

ABBREVIATIONS FOR' SERVICE .·•MJ(Ndit'
MOD~L AA-~?'S/v1/ AA~A25~ ··{.
ABBREVIATION
AC
A/D.
AFC
AGC
ALC
AM
ANT
A-SW
BUF
CK
D/A ·
DC
DET
FF
FLO (FL DISPLAY)
FM
FREQ
GND
IF
. Alternatl~g Current
Analog/Digital
. Auto
FrE:quency Control.
Ahtq,Ga,in Cbritrol
.AutoL~v61Cont~ol
Amplitude.Modulation.··
ANTenna
Analog SWitch
BUFfur
ClocK
Digital/Analog
DirectCurrerit ..
DETectof'.··
.· . ..
FlipFlop
FLuorescent•Display
Frequency Modulation·
FREQuency
.GrouND
Intermediate Frequency
PiL
REC.
RF
RST
SEG'
SENS.
SM
SSG. •
ST
. SW
'
,T;H.D
vco·
· LqngWav~
.· :i¼ob~latiort
.. : Mi.dd1{W\lv~.'
i Ivlulti' P1.eX\
... 6SCillato{ ·
Play.Back ·
Phase.Locke
RECord.
Radi9 ·.·
ReSeT
SEGfuent

•
I
(
I
COMPUTER CONTROLLED STEREO RECEIVER
AA-A25/v1
MODELAA--A25L
I'

COMPUTER CONTROLLED STEREO RECEIVER
AA-A25/Y1
MODELAA-A25L
SECTION 1 SERVICE MANUAL . . . . . . . . . . . . . . . . . . . . 3
SECTION 2 PARTS LIST
........................... 19

SAFETY INSTRUCTIONS
SAFETY CHECK AFTER SERVICING
Confirm the specified insulation resistance between power cord plug prongs and externally exposed parts of the set is
greater than 10 Mohms, but for equipment with external antenna terminals (tuner, receiver, etc.) and is intended for
~ or [Al, specified insulation resistance should be more than 2.2 Mohms (ground terminals, microphone jacks,
headphone jacks. line-in-out jacks etc.)
PRECAUTIONS DURING SERVICING
1. Parts identified by the Lt. symbol parts are critical for safety.
Replace only with parts number specified.
2. In addition to safety, other parts and assemblies are specified for conformance with such regulations
as those
applying to spurious radiation. These must also be replaced only with specified replacements.
Examples:
RF converters, tuner units, antenna selector switches, RF cables, noise blocking capacitors, noise
blocking filters, etc.
3.
Use specified internal wiring. Note especially:
1) Wires covered with PVC tubing
2) Double insulated wires
3) High voltage leads
4.
Use specified insulating materials for hazardous live parts. Note especially:
I) Insulation Tape
2)
PVC tubing
3) Spacers (Insulating Barriers)
4) Insulation sheets for tran~istors .
5) Plastic screws for fixing microswitch (especially in turntable)
5.
When replacing AC primary side components (transformers, .power cords, noise blocking capacitors, etc.), wrap
ends
of wires securely about the terminals before soldering.
6. Observe that wires do not contact heat producing parts (heatsinks, oxide metal film resistors, fusible resistors, etc.).
7. Check that replaced wires do not contact sharp edged or pointed parts.
8.
Also check areas surrounding repaired locations.
9.
Use care that foreign objects (screws, solder droplets, etc.) do not remain inside the set.
VOLTAGE CONVERSION
Models for Canada, USA, Europe, UK and Australia are not equipped with this facility. Each machine is preset at the
factory according to destination, but some machines can be set to 110V, 120V, 220V or 240V
as required. If your
machine's voltage can be converted:
Before connecting the power cord, turn the VOLTAGE SELECTOR located on the rear panel with a screwdriver until
the correct voltage
is indicated.
VOLTAGE SELECTOR
120V
2

I. SPECIFICATIONS
FM TUNER SECTION
TUNING FREQUENCY RANGE
USABLE SENSITIVITY (IHF)
QUIETING SENSITIVITY (IHF) (S/N S0dB)
CUPTURE RATIO
SELECTIVITY (IHF)
IMAGE REJECTION
IF REJECTION
SPURIOUS REJECTION
AM SUPPRESSION
S/N (IHF)
HARMONIC DISTORTION
STEREO SEPARATION
LW TUNER SECTION (AA-A25L Only)
TUNING FREQUENCY RANGE
USABLE SENSITIVITY (IHF)
SELECTIVITY (IHF)
IMAGE REJECTION
IF REJECTION
S/N
T.H.D
ANTENNA
AM TUNER SECTION (MW for AA-A25L)
TUNING FREQUENCY RANGE
USABLE SENSITIVITY (IHF)
SELECTIVITY
(IHF)
IMAGE REJECTION
IF REJECTION
S/N
T.H.D.
ANTENNA
AMPLIFIER SECTION
RATED POWER OUTPUT 20Hz
to 20kHz
lkHz
MUSIC POWER
POWER BANDWIDTH (!HF,
-3dB, 8ohms)
S/N PHONO
AUX
RESIDUAL NOISE (8 ohms)
CHANNEL SEPARATION (IHF) PHONO/AUX
DAMPING FACTOR
(lkHz, 8 ohms)
OUTPUT SPEAKER
INPUT SENSITIVITY/IMPEDANCE PHONO
AUX/TAPE
OUTPUT LEVEL/IMPEDANCE TAPE REC
FREQUENCY RESPONSE PHONO (RIAA)
AUX/TAPE
TONE CONTROL
BASS
TREBLE
PHONO
MAX. INPUT (MM)
POWER REQUIREMENTS
DIMENSIONS
WEIGHT
87.SMHz to 108.0MHz
1
L2dBf (300 ohms)
16.2dBf (Mono}/37.2dBf (Stereo)
l SdB
60dB (400kHz)
85dB
90dB
90dB
60dB
75dB (Mono)/65dB (Stereo)
0.1%(Mono)/0.3% (Stereo)
45dB
(lkHz)
146kHz to 353kHz
800µV/m
30dB
45dB
55dB
35dB
2.0%
Loop antenna
530kHz to 1610kHz for USA and Canada
53lkHz to 1602kHz for other countries
300µV/m
25dB
40dB
55dB
40dB
1.0%
Loop antenna
8 ohms
30WX2/0.05%_
33WX2/0.05%
60W
SHz to 60kHz/0.1%
75dB
98dB
0.SrnV
6SdB
(lkHz)
so ..
A or B 4 to 16 ohms A+ B 8 to 16ii>hms
2.S mV/lO0kohms
150mV/47kohms
1S0mV/3kohms
±0.SdB (30Hz
to lSkHz)
SHz
to lO0kHz -3dB
±8dB (l00Hz)
±8dB (l0kHz)
lS0mV (lkHz)
120V, 60Hz for USA & Canada
220V,
SO Hz for Europe except UK
, 240V, S0Hz for
UK & Australia
· 110V/120V/220V/240V, 50/60Hz switchable for other countries
440(W) x 80(H) x 318(D) mm
6.2kg
* For improvement purposes, specifications and design are subject to change without notice.
--------------SERVICE MANUAL AA-A25/Y,, AA-A25L--------------
4

SECTION 1
SERVICE MANUAL
TABLE OF CONTENTS
I. SPECIFICATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
II. DISMANTLING OF UNIT .... ·. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Ill -CONTROLS . . . . . . . . . . . . . . . . . • . . . . . . . . . . . . . . . . . . . . . . . . . . 6
N. PRINCIPAL PARTS WCATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
V. DESCRIPTION OF THE CIRCUIT OPERATION . . . . . . . . . . . . . . . . . . 8
5-1 AMPLIFIER PERFORMANCE . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
5-2 TUNER PERFORMANCE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
11
VI. TUNER ADJUSTMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
6-1 THE INSTRUMENT CONNECTIONS ...................... 14
6-2 TUNER, FRONT END, MPX PC BOARD ADJUSTMENT POINTS , . . 14
6-3 HOW TO CALL THE PRESET FREQUENCY FOR
THE TUNER ADJUSTMENT
............ 15
6-4 FM SECTION ADJUSTMENT ............................ 16
6-5 LW SECTION ADJUSTMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
6-6 AM (MW) SECTION ADJUSTMENT . . . . . . . . . . . . . . . . . . . . . . . 17
VII. PC BOARD TITLES AND IDENTIFICATION NUMBERS ............ 18
For basic adjustments, measuring methods, and operating principles, refer to GENERAL TECHNICAL
MANUAL.
------------SERVICE,MANUAL AA-A25/Y
1
,AA,A2SL------------
3

Ill. CONTROLS
2 3 8
8
a
10
Fig. 3-1 Front View
3-2 Rear View
1. POWER SWITCH
16.
SPEAKERS seLECTO.R (A and B) SWITCH
2.
TONE CONTROL (BASS, TREBLE) BUTTONS 17. PHONES JACK
3. BALANCE BUTTON
18. PHONO JACKS ·
4.
STATION MEMO BUTTONS (1 to 8 & 9 to 16) 19.
GROUND TERMINAL
5.
BAND SELECTOR BUTTON
20. TAPE 1 IREC/PLAY) JACKS
6. TUNING CONTROL BUTTON
21. TAPE 2 (REG/PLAY) JACKS
7.
FL DISPLAY
22.
SPEAKER TERMINALS (A and B)
8. PRESET
STATION BUTTONS
23. AC
OUTLETS
9.
INPUT SOURCE SELECTORS BUTTON
24.
VOLTAGE SELECTOR ( [ill.~ model only)
(PHONO, CD-(AUX), TAPE1 and TAPE2)
25. AC POWER CORD
10.
DIRECT ACCESS VOLUME CONTROL
26. AM STEP/FM DE-EMPHASIS SELECTOR
11. SCAN AUTO/MANU SELECTOR BUTTON
( [Q].~ model only)
12. FM
MODE AUTO/MONO BUTTON
27. RESET
BUTTON
13.
ACOUSTIC MEMO, A1 and A2 BUTTONS
28.
ANTENNA TERMINAL
14.
DEFEAT BUTTON
29. CD (AUX) JACKS
15.
SAFETY SET/CALL BUTTON
--------------SERVICE MANUAL AA-A25/Y, ,AA-AlSL--------------
6

\
,I
II. DISMANTLING OF UNIT
In case of trouble, etc. necessitating dismantling, please
dismantle in the order shown in the photographs.
Reassemble in reverse order.
1
SCREWS
2
BOTTOM COVER
SCREWS
3
4
FRONT PANEL
5
-------------SERVICE MANUAL AA-A25/Y1 ,AA-A25L-------------
5

V. DESCRIPTION OF THE CIRCUIT OPERATION
5-1 AMPLIFIER PERFORMANCE
5-1-1 General Description
(1) Functions
a) Input Selec.tor Control
This microcomputers is capable of controlling
analog switch TC9164N that
serves as the
input selector. Three input systems that.include
PHONO,
CD, and TUNER, and t,vo monitoring
systems that include TAPE 1
and. TAPE 2 may be
controlled.
b) Direct
Access Volume Control
Reads voltages detected out
of the sound-volume
touch control through an A/D converter, and sets
the electronic potentiometer in accordance with
the read data. In this process, any designated
setting will be reached from the earlier potentio-
meter position by fading
in or out.
c) Balance Control
By setting various level differences between Leh
and Reh on the main control, up to a maximum of
30dB L-R level offsets may be created.
d) Tone (BASS/TREBLE) Control
Operates the tone control potentiometer
(TC9156P)
in 2dB steps up to a maximum of
±lOdB, and thereby performs as an electronically
.controlled tone circuit. ·
f) Acoustic Pattern Storage
By this function,. stores in.the microcomputer two
patterns
of .the tone control circuit settings, and
enables the instant loading of either of the stored
patterns.
g) Volume Control Safety Function
With the touch control operated direct access
. sound volume system that· enables _the instant
setting
of any preferred sound volume level, the
danger exists that the inadvertent touch of a
higher position
of the control will cause a sudden
emission
of unexpectedly high sounds from speak-
ers.· A time lag measure in the form of fade-in's
has beeri provided
to enable coping with the
above danger, but
as an added and positive precau-
tion, this safety function has been added on that
suppresses
all sounds louder than a level set in
advance.
h) TUNER Direct Function.
This·function will set the input selector at TUNER
upon receiving data from the microcomputer.
(Al007T) for the tuner that
is output as soon as
the tuner has been operated.
5-1-2 Key Input and Dynamic FL Display
PIN. NO
®
®
©
®
®
Strobes
Key inputs and FL displays are both handled dynam-
ically, and their basic clock signals generated by the
ITMR interrupt (I ,024 Hz) for the output of strobe
signals.
R4o
R41
I -4~·~ MAX 12sI1se.:
~~~---------~n
R42
R4 3
R5 o
R5i
Fig. 5-1
5-1-3 Acceptance of Key Inputs
SINGLE PRESSING J i
. 1 I
l I
~
24msec ·
I I I
CONTINUOUS
DEPRESSIONS
---"""'1111111 ! I
I
I !L
I I
I I
I I
I
I I
I I
I
.... · :: I E.
I I
I I
31 IE 31
500ms 150 150 !50 150 !50
Big. 5-2
• Chatterings
will be absorbed for 24 rnsec.
• Continuous depressions will be accepted first at 24
msec after the depression start, second at 500 msec
after the first, and then at every 150 msec thereafter.
•
All multiple depressions · .shall be inhibited. Once a
multiple depression
is made, no key inputs will be
accepted until after
all of the depressed keys. have
been released.
5-1-4 Key Processings
(1) [PHONO], [CD]
Sets the input selector (TC9164N) for either of the
input modes keyed in, and makes due indications for
it. Nothing, however, will occur when the depressed
key mode has already been engaged. .
When either TAPE 1 or TAPE 2 has been keyed on,
the displays for a tape monitored input will be
flashed on and
off for 10 times at a 1/2 duty and
once every second, to alert the operator
of the
ongoing tape monitoring.
In addition, when serial
data
is being transferred to the analog switch, the
--------------SERVICE MANUAL AA·A25/Y
1,
AA·A25L---------------
8

IV. PRINCIPAL PARTS LOCATION
CONTROL(BJPCB
Al007A5048
SWITCH SW!
VR901
HEADPHONE JACK J2
VOLTAGE SELECTOR
SW901
HEADPHONE
PCB
Al007A501E
r- POWER PCB
I AI007A50 IB [ill
, 508B[sfil
POWER TRANS T901
AA-A25T-30[sfil
509B IE,V,B,Si
MAIN AMP PCB
Al007A501A [ill
I
SPEAKER PCB
AI007A50IG: u,c,A,E,B,S I
FILTER PCB
AI007A509D
40IE,Vi
-50 (E]J
- 70@)
508A Ls£
509A [E,B,s,v)
TUNER PCB
TI007B502A
(AA-A25J
TI0078507A
(AA-A25L)
VOLUME
MPX PCB
AI007B503A
Fig. 4-1 Front View
FRONT END PCB
A3040A5200
CONTROL (A) PCB
Al007A504A
PRE AMP PCB
Al007A503A
Fig. 4-2 Upper View
-------------- SERVICE MANUAL AA-A2S/Y,, AA-A2SL--------------
7

5-1-5 Input Selector Analog Switch (TC9164N)
Controls the electronic potentiometer (TC9176P) and
the tone potentiometer (TC9156P).
(1) Serial Data Structure
The serial data
is composed of 3 parallel bits that
include DATA, CK, and ST, and the numbers of serial
bits of the individual potentiometers have been made
as follows:
TC9164N ➔ 14 bits
TC9176P
➔ 20 bits
TC9156P
➔ 18 bits
Control lines
DATA and CK for the TC9176P and
TC9156P have been made common with control lines
ST-WR
and CE for A/D converter LC7910, because
A/D conversion and data transfers
to the potentio-
meters will never occur simultaneously, and
no
changes in the status of potentiometers will take
place as long as
no ST are issued.
a) Buffers for the
Input Selector Switch (TC9164N)
MFSRD3 MFSRD2 MFSRDl
....
0:i
N
~
0 ~
i.l-1
~
i.l-1 ~
"O
~
....
~
N
Q)
z
i.l-1
i.I.1
~
~
~
"'
0 z ::,
~
::,
;:::l
8 :I: Q
~
0 0
Q., u
00 E-< 00
0 0 1 1 0 1 1
ON
OFF
[Data Timing Schematic Diagram]
Pin@,@
DATA ( R70,91)
Pin@,@
CK(R71,92)
IIIIl_
i
'
I
lfUlJ1Jl
I
JUL
i
------ 14/20/l8 81T -----:,.;
Pin@),@
ST(R72,73)
u
0
Fig.
5-3
(2) Data Buffers
Data buffers for
the TC9146N are fonned in RAMs
MFSRDO through MFSRD3, and those for the
TC9176P and TC9156P in RAMs MVSRDO through
MVSRD4. Their allocation charts are shown in Tables
5-1 to 5-3.
MFSRDO
N m
st
u u u
1 0 0 Fixed Data
Table
5-1
Bits 2 and 3 of MFSRDI will not be transmitted.
b) Buffers for the Master Potentiometer (TC9176P)
MVSRD4 MVSRD3 MVSRD2
L R 0 2 4 6 8 0 10
20 30 40
0
c) Buffers for the Tone Potentiometer (TC9156P)
MVSRD4 MVSRD3 MVSRD2
+5 +4 +3 +2
+1
0 1
-2 -3 -4
0 0
0 0
MVSRDI
50 60 70
C1
0
MVSRDl
-5
L R
I 1
1 I
MVSRDO
C2 C3
C4
0 0 1
Table 5-2
MVSRDO
C1 C2
C3
0 1 0
1 0 0
Table 5-3
---+ Fixed Data
For BASS
For TREBLE
-------,-------SERVICE MANUAL AA·A25/Y
1,
AA-A25L--------------
10

)
electronic potentiometer will be muted, to prevent
the leakage
of switching noises to the output circuit.
(The AA-A25/L has no "TUBER" key, but the neces-
sary input selection will be made by command data
from the micro-computer (A1007T) incorporated in
the tuner.)
(2) [TAPE I], [TAPE 2]
Each single pressing of either key will switch its
monitoring status between ON and
OFF from one to
the other, and its indication also turn ON and
OFF
accordingly. In addition, during the transfer of serial
data to the analog switch, the electronic potentio-
meter will be
muted to prevent .the leakage of
switching noises.to the output.
This, however, does
not apply to TAPE l key opera-
tions with TAPE 2 in an ON mode.
(3) [VOLUME]
When the sound volume display is being made, either
fades the sound volume display
is being made, either
fades in or fades
out to the touched position from an
immediately preceding level. The phasing speed will
be 2
dB per 60 msec. However, when the touched
position
is above the "Safety" engaged position, the
foregoing operation will be made only up to that
"Safety" position.
As for the display, the touched
position (within the "Safety" range) will instantantly
be displayed upon touching.
When either the Balance or the Safety Level is being
displayed, the display will be switched to the
Volume. Operations thereafter will conform with the
above process.
(4) [BALANCE LJ, [BALANCER]
When the Balance is being displayed, data will be
transferred to provide the designated level offsets
between Leh and Reh
of the electronic potentio-
meter, and the display will also synchronize there-
with.
When continuously depressed, however, the
potentiometer setting will start varying at 500 msec
after the depression start, and will thereafter vary at
2
dB per 150 msec, but linger for 750 msec at the
center position when passing through it. (The display
will vary at 2 dB per step in the immediate vicinity of
the center position, but at 4 dB per step in all other
areas.)
When these keys are pushed while either the Volume
or the Safety Level
is being displayed, the display will
be switched to the Balance.
(5) [SAFETY]
• When either the Volume or Balance position is
being displayed:
A single press
of the key will first have.the Safety
Level position at the time displayed. This display
will revert
to the Volume position display 5
seconds later, but
if the Safety key is depressed
continuously for one second or longer, the display
will be switched to that
of the Volume, and the
Safety indicator will flash on and
off every second
at a 1/2 duty. This signifies a Safety changing
mode to have been engaged, where any Volume
level up to
Max may be selected, and the mode
will be sustained for one minute. In other words,
the one minute after the beginning
of the Safety
flashing represents a Safety Level setting time
duration,
•
When the Safety indicator is flashing on and off:
The Volume position touched in this duration
will
be set as the Safety Level that represents the
sound volume level not be exceeded by any sub-
sequent acoustic output.
As long as. the Safety
Level set
is other than the maximum potentio-
meter position, the Safety indicator
will be lit
steadily, but when it
is at the maximum position,
the indicator
will go off.
(6) [BASS+], [BASS-], [TREBLE+], [TREBLE-]
Each single pressing of one of these keys will either
raise or lower the electronic potentiometer for either
BASS or TREBLE. When it is depressed contin-
uously, the first potentiometer up/down shifting
operation will
be performed when 500msec have
elapsed since the depression start, and the subsequent
operation
at the rate of 150 msec per step. When the
shifting passes through the center position, it will
linger there for 750 msec before moving further on.
The display will also vary conforming with individual
key operations.
(7) [DEFEAT]
Restores the BASS/TREBLE positions all at the
center, regardless
of their earlier potentiometer posi-
tionings.
(8) [MEMO)
Engages an acoustic pattern storage standby mode.
At this time, the ACOUSTIC
MEMO indicator will
turn on, and the Al and A2 indicators flash on and
off for 10 times at a 1/2 duty in I-second cycles
(at I Hz).
Even before 5 seconds are up, the standby mode may
be disengaged by pushing any other key than [Al]
and [A2].
(9) [AI], [A2]
• When at Standby for Acoustic Pattern Storage:
Stores the current BASS/TREBLE positions in
the n1emory, ·and
will disengage the storage
standby mode.
• When in any other mode than Acoustic Pattern
Storage Standby:
Loads the stored BASS/TREBLE positions, that is,
sets the potentiometers instantly at those positions
and their displays at the same time.
---------------SERVICE MANUAL AA-A25/Y, ;AA-A25L---------------
9

(2) Non-Active Mode
This is a mode where the tuner performance has been
partially constrained. It
is engaged by detecting an
[H] level
of the line connected to R7
2 (A1007T
Pin 15) of the subject microcomputer, which has
been brought about by the microcomputer
of AMP in
switching the input selector
of AMP to other than
TUNER, either PHONO or CD, and by juding the
tuner thereby not to
be listened to.
Relative to the display, the frequency display will be
extinguished, and .bars displayed instead, to signify
a non-active mode.
tNPU"l" SOUAC:lilt ---i
,- n ""'""T" ,
LU&liillir I
-MHz
Fig. 5-7
Relative to the operating performance, will accept
only the
BAND, UP/DOWN, and Preset CH keys, and
reject
all the other keys.
5-2-6 Auto-Tuning
Pin@
AUTO STOP INPUT
R91 {Al007T)
SCAN POINTS
A
I
I
I
I
I
I
I
A'
8
I I
RADIO : I I RADIO
STATION I I l STATION
~I : I/
l ! Ll 1l l l l l l l l l l Li 1l
-
IOOms Fig. 5-8
The starting point in auto tuning modes may either
be a broadcast receiving point or a point where no
broadcast
is received.
Since stopping the scan merely at an [H]
level of the
auto-stop signal may therefore cause nonconform-
ities, the process employed
is to stop scanning only
when the auto-stop signal has first dropped to an [L]
level after the scanning start and then has climbed
to an [H] level.
The scanning speed is about 100 msec per step. The
step
will be a single channel spacing in the receiving
band that varies by destination. Auto-scanning
of LW,
however, is an exception to this rule and 9 kHz steps
have been assigned to it, where fixed points 9N+2 or
9N (N = an integer) will be scanned.
In other words, against any given point selected
earlier by a manual scan, the scanning start when an
auto-scanning mode
is engaged will always be at a
point 9N+2
or 9N.
9n+2
9{n+l)+2
5-2-7 Tuner Output Muting
This microcomputer will mute the tuner signal when
the
BAND data or PLL data is changed by the
[BAND], [UP] , [DOWN] , [MODE], or Preset CH
key, or when the receiving·mode is changed.
In the muting process, when 50 rnsec have elapsed
since the initial muting start, data transfer and other
processings will be made, and then, 450 msec after
these processes have been concluded, the muting
will be disengaged. We will· call the initial part
"pre-muting" and the latter trailing part "after-
muting".
The diagram below illustrates the above arrangement.
MUTING OUTPUT (R?I)
Pin@ (Al007T)
KEY INPUT
RECEPTION
i I
, I
-
50msec
MUTE ON
[
8AND ]
PULL DATA CHANG£
/
MONO/STEREO
i
450msec
MUTE OFF
Fig. 5-10
As exceptional cases, when an earlier muting process
is still ongoing upon receipt of another key input, the
50 msec pre-muting will
be omitted.
5-2-8 Key Processing
(1) [BAND]
Each single press of this key will switch the band.
The selecting sequences will be as follows:
2- BAND
3 BAND
-FM-MW-LW
Fig. 5-11
(2) [UP], [DOWN]
In a manual scan mode, each single pressing of either
of these keys will shift the receiving frequency by a
step,
and its continuous depression will have the band
scanned at 50 msec per step. In a
AUTO scan mode,
the band
will be scanned at 100 msec per step until a
station
is captured, at which time an auto-stop of the
scanning
will be exercised. In an auto-scan mode, as
soon as any other key than [UP] and [DOWN] is
pushed, the scanning will be stopped at that point.
9n
)--------0>----+----o---------<
9(n+I) START
9(n+2)+2
9(n+2)
9{n+3)+2
9( n +3)
9K
9K
~I
Fig. 5-9
--------------~SERVICE MANUAL AA-A25/Y
1
,AA-A25L---------------
12

)
5-2 TUNER PERFORMANCE
5-2-1 General Description
(1) Functions
a) 20-Ch or 16-Ch Random Presetting of Stations
When initialized, discr~mates between A45 and
A35/25, and against A45, enables 10 stations each
front
(I to 10) and back (I I to 20) or a total of
20 stations to be preset, while against A35/25,
enables 8 stations each front
(I to 8) and back
(9 to I 6) or a total of I6 stations to be preset.
The presetting permits the random storage
of
station data irrespective of band, and for FM
stations, the MONO/STEREO segregating data
will also be contained in the storage.
b) Two Tuning Styles: AUTO and MANUAL
The AUTO Scan Tuning that once the UP/DOWN
key
is pushed, will continue scanning until a
station is captured, and once it is captured, will
stop scanning, and
the MANUAL Tuning that will
scan only when
the key is held down, and when it
is released, will stop scanning, are the two tuning
styles enabled.
(LW
is shifted in lK steps for MANUAL and 9K
steps for AUTO.)
c) Switching
of MONO and STEREO Receiving
Modes
The MONO/STEREO mode switching function .has
been incorporated for FM reception, and is also
included in the stored station presetting data.
5-2-2 Acceptance of Key Input
SINGLE PRESSING J
CONTINUOUS
DEPRESSIONS
I '
--
::?4msec
I
I
I
I
I
>E--------------~
500ms
50 50 50 50 50
Fig. 5-4
• Chatterings will be absorbed for 24 msec.
• Continuous depressions will be accepted first at 24
msec after the depression start, second
at 500 msec
after the first, and then
at every 50 msec thereafter.
•
All multiple depressions· shall be inhibited. Once a
multiple depression
is made, no key inputs will be
accepted until after all of the depressed keys have
been released.
5-2-3 Initial Setting (RST Mode)
a) FL Display:
INP'UT SOURCE
TUf\l[l~'
:;.:~,ari ---i
FMAUTC
SCAN MOOlE
FM
I_/ 17
I U MHz
Fig. 5-5
b) The received frequency will be at the lowest in the
FM band for each destination:
c) The mode will be STEREO (FM AUTO).
d) The scan mode will be MANUAL.
e)
All the preset channels will be at the lowest FM
frequency.
f) The last frequencies of individual bands of the
tuner will be the lowest frequencies.
5-2-4 Status in a Backup Mode
Basically, the status immediately before engaging the
backup will
all be sustained, but slight deviations will
be involved, as listed below.
a) When a backup mode
is engaged during AUTO
SCAN, the scanning will stop.
b) When a backup mode
is engaged in a storage stand-
by mode,
the standby will be disengaged.
c) The pre-backup status will be sustained for about
3 weeks.
5-2-5 Active and Non-Active Modes at Tuner
(1) Active Mode
This is a mode after the data has been transmitted to
the microcomputer (A1007A)
of At\1P to have the
input selector
of AMP switched to TUNER, that is, a
mode where
all the tuner performance has been
enabled.
The data for
the microcomputer of AMP will be
transmitted from port R41 (A1007T Pin 2 ) when
the BAND, UP/DOWN, and Preset
CH keys have
been pushed, and its timing will be as illustrated
below.
Pin®
R41(Al007T)
Fig. 5-6
--------------SERVICE MANUAL AA-A25/Y
1,
AA-A25L---------------
ll

IV. TUNER ADJUSTMENT
6-1 THE INSTRUMENT CONNECTIONS
AM S.S.G
OUTPUT
0-
TEST LOOP
ANTENNA
APPROX
600mm
' SET
Leh OR Reh
OUTPUT
AC
VOLTMETER
Fig. 6-1 Instrument Connections for AM (MW, LW) Section Adjustment
FM S.S.G
:'XT MOD
INPUT
<>-t77---------t-t--1-0750HMS
OUTPUT
ANTENNA
TERMINAL
FM STEREO
GENERATOR
TP
GND
Leh
OUTPUT
Reh
OUTPUT
SET
DISTORTION
METER
Leh
INPUT
Reh
FREQUENCY
COUNTER
AC VOLTMETER
INPUT
AC VOLTMETER
Fig. 6-2 Instrument Connections for FM Section Adjustment
6-2 TUNER, FRONT END, MPX PC BOARD ADJUSTMENT POINTS
_J
"'
i N
)-
"'
., _J
i'
'Z
<( 0
"'
<(
z
w
(/)
,.
_J
N
u
>
@ii§
:Iii~
u
i~
i >
., uJ
~
"'
:;;
<(
FRONT END PCB
(MOl) SN3S V>J3
;;;7 Oj 17
~
~©
"' f-
';:_J
!!,
:;;;
<(
...
., ::,
~o.0
>-::1:
""
CD
u
a..
X
a..
~
CD
<..)
a..
0:::
w
z
::::i
I-
(
Fig. 6-3
--------------SERVICE MANUAL AA-A25/Y
1,
AA·A25L---------------
14

(3) Preset CH Key
a) When the Tuner is in an Active Mode:
Except when at standby for storage, a single
pressing of one of the preset channel keys will load
the front (I to 8) and back (9 to 16)side channels
under that key alternately, and the FLD will
display the number of the channel thus loaded.
When at standby for storage, the frequency
currently being received will be stored in either the
front (1 to 8) or back (9 to 16) side memory until
under the key that has been pushed, and the
·storage standby mode will then be disengaged.
b) When the Tuner is in a Non-Active Mode:
A push of one of the keys will have the front side
preset channel (1 to 8) under that key loaded, and
have data transmitted to the microcomputer of
AMP to switch the input selector of AMP to
TUNER.
However, when in the last active mode of the
tuner, a back side (9 to 16) channel had been
listened to, and that channel key is now pushed,
the loading effected will not be that of the front
side (1 to 8) but of the back side (9 to 16)
channel.
(4) [MEMO 1 - 8J, [MEMO 9 - 16]
These are the keys for storing a channel frequency
data in the Preset CH, and used for channels 1 to 8
and 9 to 16, respectively. Specifically, when either of
the keys is pushed, the MEMO Indicator will be lit,
and the channel number display flashed on and off,
to alert the operator as to which side of the Preset
CH key, 1 to 8 or 9 to 16, is being operated.
For 1 to 8: For 9 to 16:
Fig.5-12
The above mode will be sustained for 5 seconds, and
the flashing repeated for 10 times at a 1/2 duty.
When, however, the Preset CH key is pushed for data
storage, or when any other key is pushed, the storage
standby mode will be instantly disengaged.
When the tuner is in a non-active mode, nothing will
occur.
(5) [MODE]
Each single pressing of this key will switch the FM
reception between MONO and STEREO from one to
the other.
When the tuner is in a non-active mode, nothing will
occur.
(6) [SCAN MODE]
Each single pressing of this key will switch the scan
mode between AUTO and MANUAL from one to the
other, and due indications made at the same time.
-------------------SERVICE MANUAL AA-A25/Y,, AA-A2SL-------------------
13

64 FM SECTION ADJUSTMENT
! Step Adjustment Item Adjustment Point Result Remarks
Band
SW to FM
1
FMOSC
L6
12V at 108.1MHz 108.1MHz Mono input.
(in
FRONT END PCB) Display
to 108.1MHz.
Connect
DC Voltmeter to TP2.
FM
mode SW to Mono
2 Low Range
L1 to LS Less than 1 OdB
90MHz, Mono input.
Sensitivity (in
FRONT END PCB) input from SSG Display
to 90MHz.
3% Distortion Factor.
High Range
VCl, 2, 4 Less than 10d
B 106MHz, Mono input.
3 Sensitivity (in FRONT END PCB) input from
SSG
Display to 106MHz.
3% Distortion Factor.
4
For best Result, Repeat Steps 2 and 3 two or three times
Middle Range Less than 1
OdB
98MHz, Mono input.
5 Sensitivity None input from
SSG
Display to 98MHz.
(Confirmation)
3% Distortion Factor.
FM
DC Voltmeter between TPS and TP6.
6 Center Voltage
T7,T8
0V indication Tune only noise
without inter-·
ference from broadcasting.
98MHz, 60dB, Mono
input.
Display to 98MHz.
7 Distortion (Mono)
T7,T8 Less than 0.3% Confirm
that the DC Voltage
between
TPS and TP6 is within
0 ± 0.025V.
MPX
98MHz, 60dB Stereo input.
8 Free Running
VR2
19kHz Display
to 98MHz.
Frequency (in MPXPCB) Connect Frequency
Counter to
TP7 (in MPX PCB).
98MHz, 60dB, Stereo
L..CH
9 Stereo Separation VR1 More than 38dB (R-CH)
input:
(in MPXPCB) Display to 98MHz.
Minimum
output of R-CH (L-CH)
98MHz, 60dB Stereo (L-CH
or
T1
R-CH) input.
10 Distortion (Stereo) (in FRONT END PCB), Less than 0.5% Display
to 98MHz.
Confirm
that the DC voltage
T7, T8 between
TPS and TP6 within
0 ± 0.025V.
NOTES: 1. Set the internal modulation signal generator to 100% (75kHz dev. (in Europe) 40kHz dev.), IkHz of each.
2. Adjust T1 (Front End), if the proper distortion (STEREO) could not obtained in step 10. (Confirm PM
Sensitivity in case is turned more than a half turn).
-----------------'---SERVICE MANUAL AA·A25/Y,, AA-A25L--~-----------
16

)
' /
6-3 HOW TO CALL THE PRESET FREQUENCY FOR THE TUNER ADJUSTMENT
SHORT
(MOMENTARILY)
I
I
I
~=!
;:,
c.==-~.
FLD
[g]
Tuner preset frequencies for adjusting RF, IF and FM
demodulator are able to preset as follows insted of
operating TUNING control button to get the test fre-
quencies from Signal Generator.
I
~
H
1/9 2/10
I
AM AM
1 to 8 600kHz
l000kHz
USA & CANADA
9 to 16
AM AM
530kHz lO00kHz
1 to 8
MW MW
603kHz 999kHz
EUROPE 3 BAND
9
to 16
MW
MW
522kHz 999kHz
1 to 8
AM AM
EUROPE 2 BAND 603kHz 999kHz
UNIVERSAL AREA
AM AM
9 to 16 522kHz 999kHz
8
AM AM
1 to 603kHz 999kHz
SOUTH AFRICA
9 to 16
AM AM
522kHz 999kHz
CONTROL(BJPCB
[g] [g]
~
[1]
©
[1]
0 @
[1]
Fig. 64
Short-circuit momentarily two test points shown in
Fig. 64. Then select required test frequency by pushing
one
of the Preset Station buttons according to Chart 6-1.
PRESET STATION CH
3/11
4/12 5/13 6/14
7/15 8/16
AM
FM FM
FM FM
FM
1400kHz 88.0MHz 90.0MHz 98.0MHz 105.0MHz 108.0MHz
!
AM FM
FM
* FM FM
: FM
1611kHz 87.4MHz 90.0MHz 98.0MHz 106.0MHz 108.1MHz,
MW
FM FM FM FM
FM !
1404kHz 88.0MHz i 90.0MHz 98.0MHz 106.0MHz 108.0MHzi
MW
LW LW LW
LW
LW
16llkHz
146kHz 160kHz 200kHz 300kHz 353kHz
AM
FM FM FM FM
FM
1404kHz 88.0MHz 90.0MHz 98.0MHz 106.0MHz 108.0MHz
AM
FM
FM
* FM FM FM
161lkHz 87.4MHz 90.0MHz 98.0MHz 106.0MHz 108.1MHz
AM FM FM FM FM
FM
1404kHz 88.0MHz 90.0MHz 98.0MHz 106.0MHz 108.0MHz'
AM
FM FM
* FM FM
FM I
l0llkHz
87.4MHz 90.0MHz 98.0MHz 100.0MHz 108.1MHz
* = FM AUTO Chart
6-1
NOTE: For model only, Set
AM STEP SW to 9kHz, which located on the rear panel.
---------------SERVICE MANUAL AA-A25/Y,, AA-A25L---------------
15

VII. PC BOARD TITLES AND IDENTIFICATION NUMBERS
MODEL AA-A25
PC Board Title
PC Board Number ! Remarks
.
MAIN AMP PC BOARD Al007A501A
1u, Y1I
A1007A508A
~
A1007A509A jE, V, sj
POWER PC BOARD Al007A501B
!u, Y1I
Al007A508B
Al007A509C
E, V, SI
HEAD PHONE PC BOARD A1007A501E
SPEAKER
PC BOARD I Al007A501G IU,
C, A, E, S, y l I
FILTER PC BOARD A1007A509D
[y]
CONTROL (A) PC BOARD A1007A504A
CONTROL (B)
PC BOARD Al007A504B
I PRE
AMP PC BOARD Al007B503A
•
PIN JACK PC BOARD Al007B503B
TUNER
PC BOARD A1007B502A
!u, c, A, E, v, s, Y1 I
I
MPX PC BOARD Al007B507B
I FRONT END
PC BOARD A3040A5200
MODEL AA-A25/L
•
PC Board Title I
PC Board Number Remarks
.
MAIN AMP
PC BOARD Al007A509A
~
POWER
PC BOARD A1007A509C !B, El
HEAD PHONE
PC BOARD Al007A501E
SPEAKER
PC BOARD A1007A501G
CONTROL (A)
PC BOARD Al007A504A
CONTROL (B)
PC BOARD Al007A504B
PRE
AMP PC BOARD A1007B503A
PIN JACK
PC BOARD Al007B503B
TUNER
PC BOARD Al007B507A !
~
MPX PC BOARD Al007B507B
FRONT END
PC BOARD A3040A5200
-----------SERVICE MANUAL AA-A25/Y,, AA·A25L------------
18