Marantz Pm-6a User manual

MARANTZ DESIGN AND SERVICE
Using superior design and selected high grade components, MARANTZ company has created the ultimate in stereo sound.
Only original MARANTZ parts can insure that your MARANTZ product will continue to perform to the specifications for
which it is famous.
Parts for your MARANTZ equipment are generally available to our National Marantz Subsidiary or Agent.
ORDERING PARTS:
Parts can be ordered either by mail or by telex. in both cases, MARANTZ part number has to be specified. !f you order by
_ mail, fulfil MARANTZ order forms.
MARANTZ S.A.
EUROPEAN PARTS DEPARTMENT .
2, Avenue Léopold III
B-7120 PERONNES-lez-BINCHE
BELGIUM 5
TWX: 57589 SEPLT B
The following information must be supplied to eliminate delays in processing your order:
Complete address
Complete part numbers and quantities required
Description of parts
Model number for which part is required
Way of shipment
Signature:
any
order
form
or
telex
must
be
signed
otherwise
such
part
order
will
be
considered
as
null
and
void,
An PWN =
PARTS ORDERING:
Parts may be ordered from the following addresses:
EUROPE
MARANTZ S.A. MARANTZ NORSKE A.S. MARANTZ DENMARK MARANTZ GMBH AUSTRIA
European Parts Department Refstadalleen 13 Bregnergdvej 132b Wiedner Hauptstrasse 98
2, Avenue Léopold III Oslo 5 3460 Birkergd 1050 Wien
B-7120 Péronnes-lez-Binche Norway Denmark Austria
Belgium Telex: 19659 Telex: 39137 Telex: 113583
Telex: 57589
MARANTZ S.A. MARANTZ FRANCE MARANTZ BELGIUM MARANTZ SVENSKA A.B.
326 Avenue Louise Bte 32 4 Rue Bernard Palissy 45 Rue Auguste Van Zande Svartviksvangen 56
1050 Brussels 92600 Asniéres 1080 Brussels Traneberg - Box 12016
Belgium France Belgium 16112 Bromma
Telex: 26602 Telex: 611651 Sweden
Telex: 13449
MARANTZ GERMANY GMBH MARANTZ AUDIO U.K. LTD.
Max Planckstrasse, 22 Unit 15/16
6072 DREIEICH 1 Saxon Way Industrial Estate
West Germany Moor Lane
Telex: 4185316 Harmondsworth UB7 OLW
Great Britain
Telex: 935196
AUSTRALIA
MARANTZ AUSTRALIA PTY., LTD.
32 Cross Street
Brookvale, N.S.W. 2100
Australia
Telex: 24121
All of the above locations are fully equipped to take care of your total service needs. Because various countries have differing
configuration requirements, it is necessary that you contact the service facility in your particular country. in the event that
there is no service location listed for your country, please, contact the nearest facility for the necessary assistance.
In case of difficulties, do not hesitate to contact the Technical
Department at abovementioned address.
ERR em Been BRE Z*

TABLE OF CONTENTS
INTRODUCTION: i sceces ccccetn Se lore hh ee Sree ee heat aes a BMA SR a Gs WB ake aa are amc as 1
1: HRBEATURES woireue at oo pce este ode en acl eeties Rapti Aale Wien aA Bee GDR ele rbot hk Ste Baan 1
2. PAW BOARDS yiceadlsc ieee cee aoa aed soceret ganesh al anata Ga eee ORE RE RA a We a pa See Pe 2
3. TEST EQUIPMENT REQUIRED FOR SERVICING ............ 0.0002 cece ee eee eens 3
4. ADJUSTMENT PROCEDURES ............ 0.0.0 ccc ce ee eee eee e ete enn eeaes 3
5. VOLTAGE CONVERSION .. 10... 0... ccc cc ee ete ee ete eee eee eens 4
6... BROCK DIAGRAM asi ce ociod ech eek kel oe Bee Seared edb 8 Was EO Sie ew SE eae and ee Se es 5
7. DIAGRAM AND COMPONENT LOCATIONS .............0 cc cece eee ere eee teens 6
7.1. Filter Assembly (PHOO) Schematic Diagram and Component Locations............000 ee eee eteees 6
7.2 Speaker Switch Assembly (PW00) Schematic Diagram and Component Locations ............202e0005 6
7.3. Voltage Amp. Assembly (P700) Schematic Diagram and Component Locations .............00200205 6
7.4 Ripple Filter Assembly (PCOO) Schematic Diagram and Component Locations ......:......0+020208% 6
75 Loudness Assembly (PFO0) Schematic Diagram and Component Locations ............000 000s e eee 6
76 ASO Protector Assembly (PNOO) Schematic Diagram and Component Locations ......... gang a ar tede an Soat 7
7.7 Test Point Assembly (PJOO) Schematic Diagram and Component Locations .............00 000 eters 7
78 Tone Amp. Assembly (PEO1) Schematic Diagram and Component Locations...............00 000802 8
79 Tone On-Off Assembly (PS00) Schematic Diagram and Component Locations ............00002+ 000% 8
7.10 Pre-Amp. Assembly (P400) Schematic Diagram and Component Locations ..............0200e00888 9
7.11 Transistor Block Assembly (P401) Schematic Diagram and Component Locations ............0000005 9
7.12 MC Transistor Block Assembly (PM01) Schematic Diagram and Component Locations ..........-+++-. 9
7.13 Head Phone Assembly (PX00) Schematic Diagram and Component Locations ............-.2008880 8% 10
7.14
A-B
Detector
Assembly
(PLOO)
Schematic
Diagram
and
Component
Locations
.............22+2205
11
7.15 A-B Power Switch Assembly (PKO0) Schematic Diagram and Component Locations ...........---++5 11
7.16 Power Amp. Assembly (P600) Schematic Diagram and Component Locations ............. 00200228 12
7.17 Mode/Balance/Vol. Assembly (PGOO) Schematic Diagram and Component Locations .........-+-.+-+- 12
7.18 L.E.D. Power Ind. Assembly (PY00) Schematic Diagram and Component Locations ............08065% 13
7.19 Phone Input Assembly (PV00) Schematic Diagram and Component Locations ............0.-2+¢e55 13
8. EXPLODED VIEW AND PARTS LIST ......... 0.0.0... cece ee eee 14
9; PLEGTRICAL, PARIS LIST 4c4ca vias ier Pa inanel et nenetamarne toa haee USE coelate 21
10.
TECHNICAL
SPECIFICATIONS
.........
0.0.00.
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11. SCHEMATIC DIAGRAM ....... cc cc ccc ccc ce te ce te cet eee erence een etenee 32

MARANTZ
MODEL
Pm-6A
STEREO
PRE
MAIN
AMPLIFIER
INTRODUCTION
This service manual was prepared for use by Authorized
Warranty
Staions
and
contains
service
information
for
the
Marantz Model Pm-6a Stereo Pre Main Amplifier.
Servicing
information
and
voltage
data
included
in
this
manual
are
intended
for
use
by
knowledgeable
and
ex-
perienced
personnel
only.
All
instructions
should
be
read
carefully.
No
attempt
should
be
made
to
proceed
without
a
good
understanding
of
circuitry
operation.
The parts list furnishes complete ordering information. Most
replacement parts should: be ordered from the Marantz
Company. However, a simple description is included for
parts which can be obtained locally.
coveiiie wees nectean TREY
See
1. FEATURES
@ MC Head Amplifier (13 transistors for each channel)
The
first
stage
of
the
MC
head
amplifier
is
a
push-pull
amplifier
consisting
of
4
very
low
noise
NPN
transistors
and
4
very
low
noise
PNP
transistors.
The
second
stage
is
also
a
push
pull
amplifier,
and
the
output
stage
is
a
SEPP
amplifier.
The
feedback
circuit
impedance
is
reduced
as
much
as
possible
to
improve
the
S/N
ratio,
and
a
voltage
gain
of
20
dB
(10
times)
is
obtained
at
a
rated
input
level
of
125
uV.
@ PHONO Amplifier (11 transistors for each channel)
The
PHONO
amplifier
uses
a
full
push-pull
circuit
con-
sisting
of
11
transistors
for
each
channel
so
that
low
TIM
distortion
and
a
high
S/N
ratio
are
obtained.
The
first
stage
is
a
push-pull
circuit
consisting
of
very
low
noise,
high
Gm
N
and
P
channel
FETs
combined
with
a
cascode
current
Miller
circuit
so
that
degradation
of
following
stage
characteristics
due
to
input
stage
im-
pedance
fluctuation
is
prevented.
The
second
stage
consists
of
an
emitter
follower
buffer
amplifier
and
a push-pull
voltage
amplifier.
The
output
stage
uses
a
SEPP
circuit
which
is
adequate
to
drive
any
type
of
load.
The
equalizer
elements
have
very
low
impedances
compared
with
conventional
circuits
so
a
S/N
ratio
of
90
dB
is
obtained
at
the
rated
input
level.
The
equalizer
elements
are
metal
film
resistors
with
tolerances
of
1%
and
polypropylene
capacitors
with
tolerances
of
2%;
this
makes
it
possible
to
obtaine
an
RIAA
phono
equalization
of
+0.2
dB
over
the
audio
range
from
20
Hz
—
20
kHz.

Input
impedances
27
kQ,
47
kQ
and
100
kQ
are
provided
for
different
types
of cartridges
when
the
PHONO
1
input
is
selected.
The
PHONO
amplifier
output
circuit
is
provided
with
a
relay
to
mute
undesirable
noise
when
the
power
is
switched
ON
and
OFF,
and
with
a
EQ
subsonic
filter
to
reduce
turntable
rumble
and
flutter.
Quarter A System
The
quarter
A
system
automatically
switches
the
bias
current
and
supply
voltage
to
the
main
amplifier
by
de-
tecting
the
main
amplifier
input
voltage
and
speaker
current;
thus,
the
main
amplifier
operates
in
class
A
when
the
power
output
is
up
to
30W/8Q,
and
in
class
AB
when
the
power
output
exceeds
that
level.
The phase correction circuit in the detection circuit
prevents distortion from being generated even if a wave-
form with a sharp rising edge is applied.
Marantz’s
usual
superb
amplifier
circuit
has
not
been
altered
in
this
system,
except
that
the
detection
circuit
is
connected
to
the
signal
system.
Voltage amplifier
The input circuit of the voltage amplifier is a source
follower using a pair of FETs, so variation in the im-
pedance of this stage does not influence following stage
characteristics. The next circuit is a differential amplifier
using a dual transistor, followed by an active balance
loading circuit using a dual transistor.
One of the differential amplifier output signals is phase-
inverted, then both signals are applied to the push-pull
amplifier through the emitter follower buffer.
Power amplifier
The power amplifier employs triple Darlington connection
and supper high f— power transistors connected in paral-
lel.
The power amplifier uses unique push-pull circuit with ex-
cellent open loop characteristics and a 2-pole phase com-
pensation circuit, so the frequency response is flat even at
high frequencies and TIM distortion is reduced remark-
ably,
Other features
The speaker protection circuit uses a high performance
IC
and
relay.
The
power
supply
circuit
uses
a
large
trans-
former with high regulation and newly developed, large
capacity custom electrolytic capacitors.
To obtain continuous high power output, high efficiency
heat pipes are used to radiate the heat produced by the
power transistors.
2.
P.W. BOARDS
As can be seen from the circuit diagram the chassis of Model
Pm-6a
consists
of
the
following
units.
Each
unit
mounted
on
a
printed
circuit
board
is
descrided
within
the
square
enclosed by a bold dotted line on the circuit diagram.
wie etd a i etd td
OWONAMAWN=|
—_
SOMNOTARWN A
. Pre-Amp. ........-- mounted on
. Transistor Block ..... mounted on
. Power Amp. ....... mounted on
. Voltage Amp. ...... mounted on
Ripple Filter ....... mounted on
. Tone Amp. ........ mounted on
. Loudness ......... mounted on
. Mode/Balance/Vol. ... mounted on
SF HteR ss. eet ees mounted on
. TestPoint......... mounted on
. A-B Power Switch. ... mounted on
. A-B Detector ....... mounted on
. MC Transistor Block .. mounted on
. ASO Protector ...... mounted on
Tone On-Off ....... mounted on
. Phone Input ....... mounted on
. Speaker Switch ..... mounted on
. Head Phone... ..... mounted on
L.E.D. Power Ind.. ... mounted on
P.W.
P.W.
P.W.
P.W.
P.W.
P.W.
P.W.
P.W.
P.W.
P.W.
P.W.
P.W.
P.W.
P.W.
P.W.
P.W.
P.W.
P.W.
P.W.
Board P400
Board P401
Board P600
Board P700
Board PCO0O
Board PEO1
Board PFOO
Board PGOO
Board PHOO
Board PJOO
Board PKOO
Board PLOO
Board PM01
Board PNOO
Board PSOO
Board PV00
Board PW00
Board PX00
Board PYO0

3. TEST EQUIPMENT REQUIRED FOR SERVICING
This table lists the test equipment required for servicing the Model Pm-6a Stereo Pre Main Amplifier.
Distortion Analyzer
Audio Oscillator
AC VTVM
Oscilloscope
Circuit Tester
DC VTVM
aa |
Use
Distortion measurements
Sinewave and squarewave signal source
LLL
Voltage measurements (AC)
Waveform analysis and trouble shooting and ASO alignment
Trouble shooting
—
AC Wattmeter
Line Voltmeter
Variable Autotransformer (0 ~ 140V AC, 10A)
Shorting Plug
Voltage measurements (DC)
Monitors primary power to amplifier
Monitors potential of primary power to amplifier
Adjust level of primery power to amplifier
lezen
4. ADJUSTMENT PROCEDURES
@ Bias Current Adjustment
(1)
(2)
Class B
Connect JL15 and JL12 with a jumper.
Parts adjusted: RL43 and RL44
Input: ~
Output: 8Q load
Adjustment: Connect a digital voltmeter between
JJO1 and JJO2 (for the L channel)
or between JJO3 and JJ04 (for the
R channel). Wait until the voltage
stabilizes (30-60 seconds), then
adjust RL43 or RL44 so that the
voitmeter reads 14 mV.
Class A
Parts adjusted: RL39 and RL40
Input: -
Output: 8Q load
Adjustment: | Connect a digital voltmeter between
JJO1 and JJO2 (for the L channel)
or between JJO3 and JJO4 (for the
R channel). Wait until the voltage
stabilizes (30—60 seconds), then
adjust RL43 or RL44 so that the
voltmeter reads 370 mV.
Shorts amplifier input to eliminate noise pickup

5.
VOLTAGE
CONVERSION
6.
BLOCK
DIAGRAM
@ EUROPEAN MODEL ONLY
TAGE
POWER SUPPLY
To convert the unit to a different power source voltage,
change the position as illustrated in the drawing below. CAUTION
DISCONNECT POWER SUPPLY CORD FROM AC
OUTLET BEFORE CONVERTING VOLTAGE.
LOW VOL
CIRCUIT
SWITCHING
O—“ |] HEAD PHONES
SPEAKER
PROTECTION
OuTPUT
HIGH VOLTAGE
OWER SUPPLY
E
SPK SYSTEM
Voltage Conversion Chart &
w
el
=o
a = °
I< Es >
oO q a
x =o 5
oz a
53 °
aE 3 3
a
aa c s
fo} aq
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FLAT AMP
TONE AMP
_ N
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8 o ¢& &
Ww > WwW ~
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[om s >
B S
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@
VOLTAGE
SELECTOR
x
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ph Ee
nat.
28 [fb
s
a
fo}
oO
Nn w We a
g 2 48 |
Note on safety: Symbol A\ Fire or electrical shock hazard. Only orignal parts z - &«
should be used to replace any part marked with symbol A . 3
Any other component substitution (other than original Py
type), may increase risk of fire or electrical shock hazard. -§ © ©)
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7. DIAGRAM AND COMPONENT LOCATIONS
7.1 Filter Assembly (PHOO) Schematic Diagram and Component Locations 7.3 Voltage Amp. Assembly (P700) Schematic Diagram and Component Locations
|
PHOO
|
P700
;
R751
2.76(2W)
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1/2
cHOS
4.7/25V
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Pare on Ce
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721
Law gh 9
Sea eees
7.6 ASO Protector Assembly (PNOO)
7.2 Speaker Switch Assembly (PW00)
~ Schematic Diagram and Component Locations
Schematic Diagram and Component Locations
5
P¥aQGi-w? GISOHISSHY
7.5 Loudness Assembly (PF00) Schematic Diagram and Component Locations
[PFOO
_
couoness
7.7
Test
Point
Assembly
(PJ00)
Td
Schematic Diagram and Component Locations
ee ee O
JJO1 JJOZ CERTHSSS HNIO3 xe WLHAD

P400
ms
ane
sue
.
7.8
Tone
Amp.
Assembly
(PE01)
Schematic
Diagram
and
Component
Locations
me
tae
F
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|
7.10
Pre-Amp.
Assembly
(P400)
Schematic
Diagram
and
Component
Location
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7.11
Transistor
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a ° Schematic Diagram and Component Locations
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7.10 Pre-Amp. Assembly (P400) Schematic Diagram and Component Locations
7.11 Transistor Block Assembly (P401)
Schematic Diagram and Component Locations
7.12, MC Transistor Block Assembly (PM01)
Schematic Diagram and Component Locations
7.13 Head Phone Assembly (PX00)
Schematic Diagram and Component Locations
EF