Pioneer MA-62 KL User 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
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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
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T---
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i:
ri i
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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.
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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

MA.EiE
7. LEVEL DIAGRAM
EOUA tI ZERl
MIC AMP
LINE
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HIADPHON E5
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OUTPUT
HEADPHONES
FREQUENCY AT 1kHz. 0dBV- 1V
11

8. DISASSE M BLY
Removal of Side Panels (See Exploded
View.)
1. To remove the left and right side panels take
out the three securing screws as illustrated,
being careful not to lose the washers.
Removing the Bottom Cover
2. After the side panels have been removed,
there are only two screws to take out before
the bottom cover can be detached. Please
refer to the exploded view below.
Removing the Front Panel
3. First, take off all the control knobs and
slider caps, taking care not to lose the
springs from inside the individual level con-
trols and the master volume control.
4. Next, remove the two fixing screws at the
front of the front panel, and the four at the
back. Do not forget to take off the rubber
feet at the back of the panel, as these two
are attached with screws also.
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6. After the mike amp
the switch assembly
Again, the six fixing
first.
ass'y has been removed,
(A) may be taken off.
screws must be removed
The Microphone Amplifier Assembly
5. This assembly is removed by taking out the
six fixing screws as shown in the diagram
(Figure 4).
The Switch Assembly (A)
MA.CiE
The Switch Assembly (B)
7. Switch B ass'y may be removed once the
four fixing screws have been taken out.
The Volume Controls
8. The two-ganged volume controls and the
slider volume controls may be removed in-
dividually, after the microphone amplifier
assembly has been taken off, by unscrewing
the securing nuts and setscrews in each case.
SWITCH CIRCUIT-A
ASSEMB LY
AWS-060-0
SWITCH CIRCUIT-
ASSEMBLY
AWS-061-O
MICROPHONE AMPLIFIER
ASSEMBLY
AWM-056-0
13
Fis.4

9. PARTS AND
Top View
VARIABLE RESISTOR
(LEVEL)
ACX-003-0
ROUND SHADING
PLATE (A)
AEC-132-0
VARIABLE RESISTOR
(PAN.POT)
ACV-128-O
HANDLE
ANH.179-A
ROUND SHADING
PLATE (A)
AEC-132-0
VARIABLE RESISTOR
(MASTER)
ACX-106-0
SHADING PLATE (B)
AED-022-0
P.C. BOARD LOCATION
ROUND SHADING
PLATE (A}
AEC-132-0
ROUND SHADING
PLATE (B)
AEC.133-A
SHADING PLATE
AED-021-0
PHONO JACK
AKB-017-0 B (6 JACKS)
PHONO JACK-A (4 JACKS)
AKB-014-0
FUSE HOI-DER
AKR-020-0
PILOT LAMP BV, 50mA
A E L-007-0
PUSH SWITCH (POWER)
A SG-023-0
AC POWER
ADG-O05-O CORD
(A)
t4

Bottom View
SWITCH CI RCU IT.B ASSEMB LY
AWS-061-0
MIC AMPLIFIER ASSEMBLY
AWM-056-A
SWITCH CIRCUIT.B ASSEMB LY
AWS-061-0
MA-6E!
PO\AJER TRANSFORMER
ATT-203-0
AC SOCKET
AKP-002-0
PHONE JACK
(HEADPHONES)
K72-026-0
SWITCH
CIRCUIT.A
ASSEMBLY
AWS-060-0
BINDING POST
FOR GROUND
AKE-0i 7-0
PHONE JACK
(MICROPHONE)
K72-O24-O
15

10. EXPLODED VIEW AND PARTS LIST
NOTE: Any parts asterisked(* ) are sLrb ject to tleinq not supplierl
Key No. Description Part No
1
2
3
4
5
Knob (LEVEL, MASTER)
Spr i ng
Knob (memory marker)
Front panel assembly
Knob {PAN'POT)
RAA 095.0
RBK 042 B
R N K,042 A
AN B-234 A
AAB-072 0
AEC.136.4
ANE-041 A
AEC 135.A
ABA,O1 1 A
AMS OO5,A
l
B
9
10
11
12
13
14
15
16
1l
t6
19
20
21"
22'
24
25
lb
27
29
30
31
32
34
35
Knob supporter
Bottom cover
Foot
Screur M4 x 26
Side board iL)
Handle stay assembly (L)
Switch circuit B assembly
Switch circuit-B assembly
Handle
l\1ic amplif ier assembly
Handle stay assembly (R)
Round shading plate (B)
Rou nd shading plate (A)
Shading plate (A)
Shadlng plate (B)
Chassis
Shield plate
Variable resistor 25OkJ)'AC (PAN-POT)
Phone jack iMICROPHON E)
Insulator (washer)
ANG 094 A
AWS O6i O
AWS 061-0
ANH,179 A
AWM 056 A
ANG 094 O
AE C 1 33.A
AEC 132 O
AED-021 0
AED O22-O
AN A-059 C
ANH 181-0
ACV-128 0
K72 024.0
E32-045-A
Phono jack'B (6 lacks)
Phono jack A (4 jacks)
Variable resisror 100kI),A2 (LEVE L)
Variable resistor'1 00k{l'A2 (MASTER )
Phone jack (HEADPHONES)
Nut (insulator)
Washer (insulator)
Rubber gromnet
Pilot lamp BV, 5OmA
Binding post for ground
AKB 017-0
AKB 014,0
ACX,003-0
ACX 106-0
Kl2 026.0
871 031-0
E34 014-0
AEB.O34-A
AEL OO7 O
AKE 017-0
K 13-047-0
AK R-020 0
AKP 002,0
l\n49 121,A
ADG OO5 O
AEC 079-0
AMS 006 A
AAD,045 0
ASG 023-0
AN F-177 0
36
31
JO
39
40
41
42
43
44
45'.
Ground terrrinal strip (4P)
Fuse holder (AC power)
AC socket
AC socket-held metal
AC power cord
AC cord grommet
Side boarcl (R )
Knob (PO''\tER)
Push switch (POWER )
P.C. board lrolder
46
41
48
Switch circu it'A asse{nblV
Pon,er transfonrer
Connector {DlN tVpe 5P)
AWS 060,0
ATT-203 0
K93 003 B
16