Yamaha A-1 Service manual
llll
FRONT
PANEL
POWER SWITCH
~
SPEAl<ER SWITCH
@ DISC SWITCH
I®
VOLUME
0
SEALING
0
HEAD
@ BASS
ill REAR PANEL (GENERAL MODELS)
0 GNO
@ PHONO - CARTRIDGE LOAD JACKS
18)
PHONO - MM INPUT JACKS (for MM Cartridge)
6 PHONO -
CONTROL
PANEL
PHONE JACK
CONTROL
TERMINAL
MC
INPUT JACKS (for MC Cartridge)
0 TUNER INPUT JACKS
0
AUX
INPUT
JACKS
TREBLE
TONE SWITCH
~
MOOE SWITCH
@TAPE
<tJli)
INPUT SELECTOR SWITCH
@ PHONO SELECTOR SWITCH
@TAPE
@)
PRE
0 SPEAKER
@AC
@AC
@VOLTAGE
CONTROL
MONITOR SWITCH
PB/REC OUT JACKS
OUT JACKS
TERMINALS
OUTLETS
CORD
SELECTOR
Printed
YA
in
Japan
AHA
5.
78, T. T
r:I
Ii/!)
2K
C T
PACKAGE
SPECIFICATIONS
REAR
INTERNAL
DISASSEMBLY
CIRCUIT
BLOCK
ADJUSTMENT
WIRING
PRINTED
SCHEMATIC
PARTS
· · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · 2
PANELS
VIEW
PROCEDURES
DESCRIPTIONS
DIAGRAM/LEVEL
..........................................
CIRCUIT
DIAGRAM
LIST
..
p
· · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · ·
· · · · · · · · · · · · · . · . · ·
· · . · ·
...............
....................
.........................................................
DIAGRAM
................................................................
BOARDS
· ·
.... · ...............
......................................................
..
· · · · · · · · · · · · · · · · · · · · · · · · · · , · · · · · · · · . . . . . . . . . 4
·
... · ·.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
·
.... · ..
· · · · · · · · · · · · · · · · · . ·
· · ·
..
·. · .........................
:
..........................
· · · ·
..
· · . · · . · ·
....................
.. · ..
·,....
· · . . . . . . . . . 5
10
11
12
17
3
6
8
(SPECIF/CATIONS
SUBJECT
CHANGE
WITHOUT
NOTICE.)
POWER OUTPUT
DAMPING
PRE
INPUT
PHONO
TOTAL
INTER
FACTOR
OUT
SENSITIVITY
MAXIMUM
HARMONIC
MODULATION
SIGNAL/NOISE
RESIDUAL
FREQUENCY
TONE
CHANNEL
POWER BAND WIDTH
N.D.C.R
HEAD
SPEAKER
AC
OUTLETS
POWER SOURCE
DIMENSIONS
NOISE
----------
RESPONCE
CONTROL
SEPARATION
PHONE
TERMINALS
WEIGHT
ACCESORRYS
an
4n
an
an
OUTPUT
IMPEDANCE
/IMPEDANCE
TUNER,
PHONO MM
PH
INPUT
PHONO
PH
DISTORTION
TUNER +
PH
PHONO
DISTORTION TUNER +
------PH-O-NO~M---C~(A------c-cN-=E=T-W--=-o-R~-K-,--)--70-,---d.,--B
PHONO MM (A NETWORK) 85d8
TUN }
AUX
TAPE
------·-·----···---
TAPE TONE
DISC
·---------------
TONE OFF J
TUN I
AUX
TAPE
RIAA
TUNER +
PHONO MM +
PHONO
an,
PHONO MM +
SWITCHED x 2
UNSWITCHED x 1
US
General Model
European Model
North European Model
British & Australian Models
0.02%
0.05%
LEVEL/
AUX,
TAPE
ONO
MC
MM
ONO
MC
SP
OUT
ONO MM +
MC
SP
+ R
OUT
REC
E_C_O_U_T
TONE OFF
ON
f
------------------
\
SP
OUT
DEVIATION
SP
OUT
SP
MC + SP
35W, 0.03%
SP
& Canadian Models
OUT
ON
(8rl)
OUT
OUT
OUT
70W + 70W, (20 - 20KHz)
80W + 80W, (20 - 20KHz)
85W + 85W, (DIN)
100
(1
KHz)
2V/600n
200mV/47Kn
2.5mV/47Kn
60µV
/1
(200pF)
on
230mV (0.01%, 1 KHz)
6mV
(0.01
%,
1 KHz)
Less
than 0.01%,
Less
than 0.005%,
___
L_e_ss_t_h_an_0._0_1
Less
than 0.003%,
35W, 60Hz : 7KHz = 4 : 1
___________
°_Ya~,
112d8
105d8
--
--
-------------·----
Less
than 50µV
TONE OFF
10Hz±0
(
1 00KHz 0 +
20-
TONE
10Hz - 4 ± 0.5dB
ON
[
100KHz o::'::gds
20-
20-
20KHz 0
BASS
±0.2d8
:20Hz±10dB
(TURN OVER
TREBLE
:20KHz±10dB
(TURN OVER
70dB
(1
KHz,5.1
75dB
(1
KHz,5.1
75dB
(1
l<Hz,PHONO short)
10-
50KHz
6mW - 70W
(0.1%
A NETWORK
39mW (Brl)
4n-16rl
100W,
(MAX
TOTAL)
100W
(MAX)
120V, AC60Hz
110/120/130/220/230/240V, AC50/60Hz
110/120/130/220/230/240V, AC50Hz
220V, AC50Hz
240V, AC50Hz
435
(W)
x 117 (H) x
15.8
kg
(34
lb
13
CARTRIDE
COAD PLUG
PHONO SHORT PLUG x 2
8rl,
20-
20KHz, (35W)
20
- 20KHz, (8V)
2_0_-_2_0_K_H----'z,_(_2V-----'----)
__
(8rl)
_
~dB
20KHz'-gdB
20KHz::'::~dB
FREQ+
FREQ+
350Hz)
3.5KHz)
Krl)
Krl)
VOL
-30dB
VOL
-30dB
VOL
-20dB)
381
(D)
oz)
(47Krl
(68Kn
x 2)
x 2)
------------------------------------------3
..,
US & CANADIAN
..,
EUROPEAN
,v
BRITISH & NORTH
MODELS
MODEL
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=
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© •
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AUSTRALIAN
@GND
@ PHO NO -
@PHONG
TERMINAL
CARTRIDGE
- MM
e PHONO - MC
@lj)TUNER
f@AUX
INPUT
INPUT
MODEL
INPUT
INPUT
JACKS
JACKS
"
LOAD
JACKS
JACKS (for MM Cartridge)
JACKS (for
MC
Cartridge)
@TAPE
(ID
@)SPEAKER
llm)
@AC
PB/REC
OUT
PRE OUT JACKS
TERMINALS
AC
OUTLETS
CORD
JACKS
\\lf.lVOLTAGE SELECTOR
© •
© •
4--------------------------------------------
TTOP
VIEW
VR &
SW
CIRCUIT
PRE
AMP
CIRCUIT
q[l)
SPEAKER SWITCH
~
POWER SWITCH
DRIVE
{@HEAT
CIRCUIT
SINK
BOARD
BOARD
BOARD
@POWER TRANSISTOR
@POWER
@,
ELECTROLYTIC
®ELECTROLYTIC
@POWER
,jfi\)POWER
CIRCUIT
CIRCUIT
18000µ F
/63WV
TRANSFORMER
TRANSFORMER
BOARD
CAPACITOR
BOARD
CAPACITOR
v
BOTTOM
VIEW
$ PHONES JACKS
@)TONE
CONTROL
CIRCUIT
BOARD
@)
TONE SWITCH
~
MODE SWITCH
@TAPE
@J
@TUNER
~
@l
@PREAMP
@
ill)
® POWER
~
®
~
,;!it)
AUX
MONITOR
SWITCH
SWITCH
SWITCH
PHONO SWITCH
PHONO SELECTOR SWITCH
DRIVE
FET
CIRCUIT
CIRCUIT
CIRCUIT
BOARD
BOARD
BOARD
TRANSFORMER
POWER
ELECTROLYTIC
POWER
PIN
TRANSFORMER
CIRCUIT
CIRCUIT
JACK
CAPACITOR
BOARD
BOARD
CIRCUIT
BOARD
1.
Top
cover removal
The
top
cover
screws
2.
Bottom
The
bottom
(13)
screws in
3.
Front
a.
Pull
knob
b.
Use
a 2
screws
VOLUME
and
at
the
VOLUME
c. Pull
sealing panel
at
cover removal
panel removal
the
out
mm
of
the
out
can be removed when the (1)
the
rear
cover
Photo
(left channel) front part
and
remove.
diameter
the
knob,
same
knob.
the
BASS and TREBLE knobs inside the
and
d. Remove screws (14)
e. Remove screws (1)
front
panel
* Make sure
lead wire
gently.
that
connections
and POWER switches.
to
of
the
can
unit
(see
photo)
are removed.
be
removed when the (5)
(4)
to
1 are removed.
of
the VOLUME
hexagonal wrench
to
loosen
the
(right channel) inside part of the
pull the knob
time remove the
out
from the shaft,
nut
used
to
mount
remove.
to
(18)
in
to
you
(3)
Photo 1.
in
Photo 2 and pull
do
not
break the pilot lamp
with
the
out
the
DISC, SPEAKER
~~-~~;===.·····.h.oic1e,·.~--:·-~-=-
Pi
4. Power printed circuit board removal
a. Remove
the
top
b. Hold the (1) and (2) holders shown
between small pincers and push them
of
the
arrow
to
~~~o
lol
lomp
cover. (Refer
~, · ...•
1 I Front
...•
(n;llrr=i
~-i:!.))IL--10
~I
Rear
to
I
I
of
switch
Step
remove them. Now pull
1.)
in
panel
in
the
direction
the
Fig. 1
Photo 3
power
printed circuit board up and remove.
* When replacing
tions
of
pins and of
the
the
power printed circuit board connector
printed board, check
the
electrolytic capacitor printed
the
posi-
circuit board.
5. Electrolytic capacitor printed circuit board removal
a.
Remove
the
top
and
bottom
covers. (Refer
to
Steps 1
and 2.)
b. Remove
Step
c. Detach
terminals on
4.)
the
power printed circuit board. (Refer
the
lead wires which are connected
the
electrolytic capacitor printed circuit
to
board.
d. Remove screw (4)
band which serves
in
Photo 2 and then remove
to
secure
the
electrolytic capacitor.
* When replacing this circuit board, make sure
TR137
into close
Fig. 2.
(9) and
contact
TR138
(10)
in
with the heat sink
Photo 2 are brought
as
shown
to
the
the
that
in
f. Pull
out
the
pilot
lamps of the DISC, SPEAKER and
POWER switches from
switches, taking care
wire connections. (See Fig.
the
that
holders
you
1)
do
at
not
the
break
rear
the
of
the
lead
9.
Tone control printed circuit board
a. Remove
b. Remove hexagonal
then
the
the
tone
front
control
panel. (Refer
nuts
(8)
printed
to
to
(10) in
circuit
Step
board.
3.)
Photo
6 and
6.
Drive printed circuit board
a.
Remove
and
b.
Disconnect
terminals
c.
Hold
between
of
printed
7.
VR
a.
Remove
b. Push
from
c.
Remove
d.
Pull
printed
remove
the
top
and
bottom
2.)
the
lead wires which are
on
the
drive
the
(1) and (2) holders
printed
small pincers and push
the
arrows
circuit
& SW printed circuit board removal
the
the
out
circuit
the
to
board
the
front
(3)
and
rear
and
screws (5)
the
connectors
board,
board
remove
up
DRIVE
panel. (Refer
(4) plastic rivets
remove.
and
detach
itself.
removal
covers. ( Refer
circuit
shown
them
them.
Now pull
remove.
G.
and
BOARD
to
(6)
in
Photo
and pin jacks
the
lead wires and
connected
board.
in
the
Step
3.)
shown
5.
of
the
to
in
Photo
direction
the
Photo
in
Photo
VR &
Photo
Steps
to
drive
then
the
5
SW
10. Power transformer
a. Remove
the
top
removal
and
bottom
covers. (Refer
to
Steps 1
and 2.)
b. Remove screws ( 1)
Photo
7) and
panel
back.
4
at
either
side
then
loosen screws (2) and lean
of
the
rear panel (see
the
rear
1
5
c. Detach
power
circuit
wires
d.
Remove screws (4)
and
11. Pin
a. Remove screws (1)
shows a
b.
Lean
under
the
lead wires which are
transformer
board
connected
and electrolytic
as well
as
to
the
to
then
jack
the
remove
printed
US
'a'
the
power
circuit
& Canadian models.)
rear panel back, referring
and
'b'
of
to
the
fuse.
(7) and (8)
transformers.
board
to
(7)
Step
AC
and
in
10
connected
capacitor
outlets
to
pin
Photo
(power
(11)
jack
to
and
8.
the
to
the
printed
the
lead
in
Photo 4,
removal
(The
photo
procedure
transformer
removal).
5
c. Detach
circuit
the
board,
four
and
pin plugs
then
remove
of
the
pin jack printed
the
board
itself.
8. Preamplifier printed circuit board
a.
Remove
b.
Remove
(1)
*
c.
Detach
connected
and
the
screws (1)
and
(2)
Remove
remove
the
then
the
front
in
the
Photo
panel. (Refer
to
(7)
4.
VR &
in
SW
to
Step
Photo 6 as
printed
circuit
3.)
well as screws
screw (7). ·
lead wires and
to
the
preamplifier
board
itself.
the
connectors
printed
circuit
board
to
which are
board
Photo
12. Power
a. Lean
ing
to
under
fuse
replacement (the fuse rating differs accord·
the
destination
the
rear panel back, referring
'a'
and
'b'
of
of
the
Step
model)
10
removal).
b.
The
fuse
holder
is
8. Replace
6
the
fuse
with a 7.0AT,
located
behind
-------------------------------------------7
to
(power
the
screw in
250V
Photo
the
procedure
transformer
unit.
Photo
8
Photo
9
CIR
MC
head
The
MC
configuration
circuit
transistors
serve
to
Principle behind noise reduction with parallel connection
It
is
assumed
e2,
have
the
resistors
the
output
e0=e1 x R2/R1 + R2+e2x
U!T
amplifier circuit
head
amp
which
inside
the
are
connected
effectively
that
internal
and
signal
voltage
DESCR!PTIO
I ifier
circuit
is
C-2's -head
reduce
the
two
resistances
e0
will
used
similar
to
amplifier
in
complementary
the
noise
signal
R 1
sources
are
be:
that
sources
and
R1/R1 + R2}
in
the
A-1
of
the
IC. Low-noise
in Fig. 1,
R2,
respectively.
parallel
components.
connected
features
equivalent
and
e1
and
in
parallel,
...
1
r
Fig. 1
In
the
same
way,
the
a
If
vectors
Fig. 2,
way,
two
Based on
following
noise
(N}
In
parallel
3dB
there
accompanies
the
overall noise
Contrary
direct
source
number
signal
*
*
*
will join
the
the
noise
of
the
is
reduced
connected
dB=
10 log10N (2)
the
case
connection
(theoretical
are
current.
to
proportion
resistance,
of
source
Voltage
sistance)
Current
tion
to
Thermal
which
increases in
the
signal
noise
same
this
formula
of
the
two
the
It
components.
the
parallel
resistance.
noise
noise
the
signal
noise
source
second
at a 90°
components
can
be
amplifiers
approach,
between
(dB}
and
in
parallel:
A-1
's MC
brings
value}.
types
of
voltage
is
therefore
voltage noise,
to
and
connections
(noise
(noise
source
of
the
resistance.
part
angle. This
considered
the
so
proportion
will be 1
are
connected
it
is
the
the
number
head
about
However,
noise
in
and
the
necessary
thermal
it
is
necessary
unrelated
which
increases in
resistance}
signal
will be 1
reduced
possible
degree
amplifier,
a noise
as
an
amplifier:
other
the
current
noise
which
to
the
source
to
the
/2e2
means
/y'2
by
in parallel.
to
come
by
of
amplifier
the
reduction
shown
that
accompanies
to
subtract
of
to
determine
agrees
signal
direct
resistance
square
and
that,
as
e0.
In
3dB
when
to
which
stages
two-stage
in
Fig.
one
that
noise
is
the
signal
with
source
propor-
(noise
root
the
in
this
the
the
of
3,
the
in
the
the
re-
of
If
e1
is
then
phase,
no
If
will have
ponents
the
each
remaining
Considered
between
conceivably
the
equivalent
e0 = e1 = e2,
the
same
the
and
noise
amplifier,
the
first
part
two
voltage
two
so
components
unchanged
from
output
the
e1 x R2/R1 + R2 = 1/2e1
and
signals
e0.
amplifiers
same
the
value
at
times
total
two
signals will be
an
average
of
the
to
phase
right
e2
and
when
e1
are
canceled
are
with
of
e0
will
configure
being
in
the
same
perspective,
of
90°.
half
of
90°
if
R1
is
and
e2
out
connected
respect
will
not
canceled
·:
separate
phase.
the
neither
From
formula
R1 = R2
equivalent
have
the
and
there
in parallel,
to
the
signal
change.
th
However,
signals in
out,
and
phase
difference
0°
or
is
observation,
(1) will be:
to
R2,
opposite
will be
they
com-
at
times
180°
but
Signal source resistance
Fig. 3
Fig. 2
L
C
DIAGRAfJl/LEV
DiA
R
J
ST
BEFORE MEASUREMENT
•
After
the power switch
• Connect
@
VOLUME
dummy
load resistance (7aW)
CONTROL +
is
push
on, wait 3 - 4 minutes before measuring,
to
the speaker terminals.
MIN
to
be
sure
of
the most stable operation.
MC
AMP
MC~
PHONO
&,
......-
MC!
MM(i::»-----::;;--0"°
CARTRIGE
LOAD
TUNER(Ol-------,---------'--0...-0---,---<o,,_
AUX(OJ~---~--;------'A~U~X~
II~
MC
RELAY
AMP
TAPE
PB
(OJ-------,,---------'
{dBml
+40
+30
+20
+10
a
PHONO
I
I
I
-PHONO
AUX
MM (!kHz)
MC
(I kHz)
-JO
-20
-30
-40
-50
-60
-70
1-81.91
-90
EO
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I
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I
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I
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:;
I
I
I
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I
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I
AMP
PHONO
I
TUNER
I
I
INPUT
SELECTOR
EQ
AMP
1,r-------------
ON
VOLUME
;,-~---------a_
TC.AMP
w
ON
o.
...
"'
TONE
CONTROL
I
I
I
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I
I
TONE
I
I
I
I
MAX
I\
\
~IOdB
VOLUME
I
I
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'
CONTROL
+IOnB
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DISC
-----
>
STEP
2
.
POWER
EQALIZER
DC
MC
I ,
I ,
I ,
1,'
ON
~'
MAIN
AMP
'I
PHONES
'
Distortion
3
Suplly Voltage
AMP
Offset Voltage
AMP
POWER
P.C.B
PRE AMP P.L.B
VR4a1
VR4a2
VR &
VR3a1
VR3a2
(L
(R
SW
(L
(R
CH)
CH)
P.C.B
CH)
CH)
Digital Multi
Meter
Digital Multi
Meter
Audio Frequency
Generator (2aKHz,
2aKHz
>TERMINALS/
TEST
POINT
POWER
PRE AMP
TP1
TP2
REC
(L
(R
OUT
R.C.B
P.C.B
CH)
CH)
JACK
3V)
PATING
OR
STANDARD
+35 ±
1V
-35 ± -a.5V
av±
2aamv
Distortion+
RE-
MARKS
Fig. 1
Fig. 2
Min
Fig. 3
Distortion ratio
CH)
P.C.B
CH)
Meter
Digital
Multi
Meter
Digital Multi
Meter
DRIVE
TP1, TP2
TP2, TP4
P.C.B
(LCH)
(R
CH)
Electrolytic
Capacitor P.C.B
TP1, TP3 (L CH)
TP2, TP4
(R
CH)
OIUlf/\L
/v\LJLTl/vlETEn
<lil
POWER
·-35
:_
IV
av±
7.4 ±
VOLTAGE
---35 '.::O.SV
10mv
Fig. 4
2mV
Fig. 5
----··
RELAY
.. · DRIVE
4
DC
POWER
lndring Current
5
MAIN
AMP
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
REC
OUT
I
CIRCUIT
Offset Voltage
AMP
DIGITAi_
MULTIMETER
19
DC
offset
OV
· IOmV
Audio frequeucy
Generator (
201<.Hz
[ill§]0
o
a~
eaiDDDee
DOD
Fig3
DRIVE
P.C.B
VR5a1 (L CH)
VR5a2
(R
Electrolytic
Capacitor
VR1a1 (L CH)
VR1a2
)
(R
--------------------------------------------10
PIN
JACI(
CIRCUIT BOARD
1.
PINJACK
VR
S.
SW
CIRCUIT
BOARD
(21
NA07044
NA07136:US
GA61890
-------.,
VI r
I
I
I
WH,
BR
I
OR I
AC
WHI
OR
8.5V
3BV
0
38.2V
6.5V
38V
I
I
I
I BE
I
I
I
I
I VI
I RE
I
I
I
I
HL E
HR
BE
WH
WH
OR
OR
VI
RE
BL
BE
WH
VI
OR
OR
BL
BL
ns-35tR
NA07044
NA07136:
US
MOOEL
E
RE
ELECTROLYTIC
CAPACITOR
CIRCUIT
NA07130
NA07 I 29:
BOARD
US MODEL
>12
>12
MODEL
L.~-3,~_J
GY
L----------------~
'-----------------~
GY
E RI
0
a::
.J
w
0
0
"'
OJ
0
::E
f-
a
~
a::~:...:
U
Otf>
w
br::
>
,::{,::{
zz
2.
FET
CIRCUIT
CIRCUIT
BOARD
BOARD
NA07042
NA07046
UNSWITCHED SWITCHED
•WIRE
BL
BR
RE
OR
YE
GR
II>
BE
Pio-
S,.
II>
Ii>
Ii>
II>
COLOR ABBREVIATIONS
Black
Brown
Red
Orange
Yellow
Green PK
VI
GY
WH
GG
SB
Pio-
Ii>
!lo-
Ii>
11>
Ii>
Violet
Gray
White
Grass Green
Sky Blue
Pink
Blue
NA07133:
NA07132:
NA7176
NA7134
NA0704
CANADIAN MODEL
US
MODEL
· EUROPIAN a BRITISH MODELS
. EUROPIAN, SEC MODEL
I : GENERAL a
3.
PREAMP
AUSTRALIAN
CIRCUIT
MODELS
BOARD NA07043,
TR411
NA07135:
TR409
US
TR403
model
TR407
TR405
SP
TR40I
FET
CIRCUIT BOt\RD
11
----------------;..,_--------------------------12
TR4I4
TR4I2
T R4I0 T Fl404
TR408
TR406
TR402
---------------------------------------------
4.
VR
&
SW
CIRCUIT
---------
BOARD
NA07044,
TR302TR304
-----------------:----
NA07035:
US
model
only
5.
TONE
CONTROL
CIRCUIT
BOARD
NA07045
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