Pioneer MA-62 KL Service Manual
<ART-084-0>
SERVICE
MANUAL
MIXING
AMPLIFIER
MFEiE
KL
<t
4to2Y
1 1D>
()ProNEeR.
MA-CiE!
CONTENTS
I.SPEC|F|CAT|ONS
.....2
2. CONNECTION DIAGRAM
..
. . . 3
3. NAMES OF
CONNECTORS ON
THE
BACK PANEL ...., 4
4.FRONTPANELFACILITIES
....5
5. BLOCK DIAGRAM
... 7
6.C|RCU|TDESCRTPTTON...
.....9
7. LEVEL
DIAGRAM .. ..
.
. . .11
S.DISASSEMBLY..
....12
9.
PARTS AND
P.C.
BOARD LOCATION
. . .. .14
10.
EXPLODED
VIEW
AND
PARTS LIST
. . . .
.16
11.
SCHEMATIC
DIAGRAMS, P.C. BOARD PATTERNS
AND
PARTS
LISTT
11.1
Circuit Connection
Diagram and Miscellaneous Parts . . .19
11.2 Switch
Circuit-B Assembly
. . . .22
11.3
MicrophoneAmplifierAssembly
......23
11.4
SwitchCircuit-AAssembly
......33
12.
PACKING METHOD
AND
PART NUMBERS ......36
,1.
SPECIFICATIONS
SEMICONDUCTORS
lCs...
........2
Transistors
.....22
Diodes
........3
lnput Select:
CH1, CH2:
MIC
i
PHONO
CH3, CH4,
CH5, CH6: MIC
/
LINE
Output
Channel
Select:
CH1,CH2,
CH5,CH6: L/ L& R
/
R
CH3,
CH4
(PAN-POT):
L
-
R
(Panoramic
Potentiometer)
I nput
(Sensitivity/l
mpedance)
:
MIC:
0.25mV
l4.lkS]"
PHONO:
2.5mV
/
50kS)
LINE:
50mV
i
50kfi
MIC Attenuator:
0dB,
-20d8
MIC
Overload Level: 250mV rms
(at
attenuator
-20d8)
PHONO
Overload Level:
250mV rms
(at
ikHz)
Output:
Stereox
2
(parallel)
Rated Output Level: 330mV
Harmonic Distortion Less than
0.2o/o
(at
1V
output)
Maximum
Output: 5V
(T.H.D.=
0.5%,50k0 load)
Channel Separation: More
than 70dB
(at
l
kHz)
Cross-talk:
More
than 70dB
(at
l kHz)
Frequency Response:
Mlc:
2}Hzto 15kHz
(19d8)
PHONO:
R IAA Equalization:
t0.5dB
LINE:
2OHzto2SkHz(1?Oe)
MIC Low
Cut: fc- 2OOHz
(6dB/oct.)
Channel lnterference:
Less than 1dB
Residual Hum
&
Noise: Less than
0.05mV
S/N
(lHF,
Short-Circuited, A Network)
MIC:
52dB
PHONO:
60dB
LINE:
67dB
Headphone
Output:
Maximum
260mV
(8Sl)
MISCELLANEOUS
Power
Requirements:
AC 120V,
60Hz
Power
Consumption:
5W
Dimensions: 400tW)
x 132(H)
x
264(D)
mm
(15-3/4
x
5-3/16
x
10
3/8 in.)
Weight: Without
Package:
5.8k9, 13 lb
With
Package
7.3kq, 16 lb
FURNISHED PARTS
Connection
Cordwith Pin Plus
. . . . .
. .
1
Operatinglnstructions
.......
1
NOTE: Specifications
and
the
design subject to
posslble
modification
without
notice
due to improvements.
MA.EiE
2.
CONNECTION
DIAGRAM
'o'
I
;tFF;:':l
,e-iai
Q
r"o*.,
SPEAKER
SYSTEN4S
LEFT
CHANNEL
RIGHT CHANNFI
rrr
STEREO TAPE DECK
(for
recording)
STEREO TAPE
DECK
(for
playback)
STER EO TURNTABLE
INPUT
TERMINALS
(AUX)
F
USE
120V
mociei
1A
ee
e
lr
t_:
T---
@
0
:l
i:
ri
i
""t
I
i;
AC
5-Line
Voltage
model
0.5A
220v
240V
1A
1 10V
1
20v
1
30v
i
L-ry4\tr"-i
MICROPHONES
cord
i
iit
ft
@
]
GROUND
TT
HF
.ii:{
t:;:;:;
":'U:t"
STEREO HEADPHONES
(for
monitor)
C
oO
Oo
O.
C
e.
Oec c OccO
3.
NAMES
OF
CONNECTORS
ON THE
BACK
PANEL
LINE
TNPUT
TERMTNALS
(CH
3,
4,5,6)
HONO
TNPUT
TERMTNALS
(CH
1,CH 2)
Outputs
from
stereo tuners, from the recording output of
a
power
amplifier,
or from tape decks, are
connected
to
these inputs.
OUTPUT TERMTNALS
('.t,
2)
!fn.r.
outputs
are for
connecting to the inputs of a
tape
ldeck
or the
auxiliary terminals of an amplifier.
I
There are two
kinds of OUTPUT
2 terminals;
the 5-pin
iOtN
type connector
may be
connected to a DIN
plug
of
i
rape
deck
for recording.
lAt
the same time, the input terminals of
pre-amplifier
may
I
be connectecJ to
phono
type
terminals.
I
I
l
l
PHONES
f
ACK
This
jack
is
for
stereo headphone
connection.
The
monitor function
of the
headphone will
enable
you
to set
a
good
balance
between
the input
sources distributed to
both
stereo output
channels.
NOTE:
l|e recommend
the use
of
tightly
fitting
headphones
such as
Pioneer
model
SE-305 effective
in
sealing
out the outside sound.
This'set
of terminals
is for connecting a stereo turntable.
You
should use a
moving magnet
type
phono
cartridge.
MICROPHONE
I NPUT TERMI NALS
Microphones
should be connected
to
these
iacks.
The MA-62 functions
superbly
whether
you
use
low or
high
impedance
microphones.
The
upper
iacks
are used to
connect
5-pin
DIN-type
plugs
and the lower to connect
usual
phone
type
plugs.
When in
simultaneous connections
to both terminal sets only the
phone
type
jacks
are
operative.
I
-
-
GROUND
TERMINAL
lf
the
turntable
used
has
a
ground
wire,
connected to this terminal.
it should be
6.
CIRCUIT DESCRIPTION
Signal
Path
1. T'he
signals
from
the microphone terminals
and the
phono
terminals
(of
channels 1
and
2
only)
are amplified by the two NPN
transistors
in the direct
coupled NFB-type
amplifier
after
selection
with the input
switches.
2.
Both the standard
jacks
and the DIN type
connectors can be used
for
the microphone
inputs,
but as
the
standard
jacks
defeat
the
DIN
connector,
it is
not
possible
to use
the
standard
jacks
when a microphone is
con-
nected
to the DIN type connector for the
same
channel.
If two
microphones are
plugged
into the
same channel at the same time, only
the one
plugged
into the standard
jack
can
be
used.
3. The
amplified signals
from
the microphone
or turntable
are
next
fed
to the resistors in
the mixing
stage through the slider type level
controls of each channel
(except
3 and
4,
which have
pan-pots)
and
the
output chan-
nel selector
switch.
4.
The signals mixed
by
the resistors in
the
mixing stage
are
then
amplified
in
the direct
coupled amplifier,
by
the
PNP
and the NPN
transistors
(2
transistors in all).
5.
The
signal taken from
the
NPN
transistor
emitter
(emitter
follower)
passes
through
the
MASTER
VOLUME
potentiometer
to be
amplified in another two-transistor
direct
coupled
amplifier
and then sent
to the
output terminals
from
the
emitter follower.
INPUT
MA-EiE!
6.
The
output
terminals
have both
phono
jacks
and a DIN
type
connector. The two
pairs
of
phono
jacks
and DIN
type connector
are
wired in
parallel,
so they
can be used simul-
taneously,
if necessary.
7.
The
headphone
output
signal
(for
monitor-
ing
purposes)
is
a
portion
of the
output
which
appears
at the output terminals,
am-
plified
by
an integrated
circuit.
The
Microphone and
Equalizer
Amplifier
Stage
Figure
1 is a
simplified
circuit diagram of
the
microphone/equalizer amplifier
for
channels 1
and 2. The switching between the equalizer
function
and
the
mike amp
function is effected
by
the switch
marked S.
The
microphone
input
terminal
has
a sensitivity
of 0.25 mV
while
the
phono
input
sensitivity is
2.5
mV
at
lkHz in each
case,
so
altering the
gain
by merely
switching the CR
element
of the
closed
loop
NFB would
cause
instability,
which
would lead to distortion
and
noise.
Therefore, the amount
of the current NFB
from
first
stage
transistor
Q1
is
changed
by Sa,
and the CR
element is
switched, to
determine
the
frequency
characteristics,
by Sb.
OUTPUT
PHONO-MlC
PH0NO*MlC Fig.
1
Mixing
Stage
The
mixing
circuit
of this unit is
a very
ortho-
dox
and highly
stable
series
resistance
circuit
using isolation
resistors.
Resistors
RMr
thru
RM6 in the
diagram
are such isolation
resistors.
The
signals
to be
mixed
are
fed
to terminals
A
thru
F,
and
perfect
mixing is
obtained
at
point
X in
the
diagram.
If low resistance
values
are
used as RM's,
changes in the
signal levels from
each
source
may
occur
due to the
different
output impedances
of the sources
connected
to
A thru
F.
To
prevent
this,
resistances
of
33OkSl
are
used
as RM's
in this unit-differences
due to
output impedance
are negligible.
To
prevent
interference
between the various
signals,
the
impedance
at
point
X
(the
mixing
point)
must
be
kept
quite
low
in relation
to the RM values.
To
fulfill
this
condition,
parallel
feed-type
NFB
is applied from
the emitter
of
Qq
to the
base of
Q:
in
the
mixing
ampli{ier. This not only
helps
to
reduce
distortion
and noise
(the
effect
of
NFB),
but
also keeps
the
input
impedance
of
Q3
verj low,
maintaining
stable operation.
cc
o
F
(J
uJ
J
LU
a
F
f
o-
F
l
o
L
)
O
cr
F
z
o
C)
J
Lri
ui
I
MIXING
CIRCUIT
(L
CHANNEL)
RNF
OUTPUT
RM,
-RM6:
ISOLATION
RESISTORS
(330k,f2)
RNF:
NFB
RESISTOR
(560ks-,)
L&R
RM,
RM,
RMe
To
Mixing
Circuit
(R
Channel)
Fig.2
10
Loading...