Marantz PM243 - 2 Function of each Part; APM RORAOS con Cins Sasuke N Eeenanedaurueie Canta Tenance Eaeees Need; CCC; Eee Eee Teen Anne Eenes Wee Eeees

MODEL PM243/143 STEREO PRE MAIN AMPLIFIER
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SMODEL #263
INTRODUCTION
This service manual was prepared for use by Authorized
Warranty
Stations
and
contains
service
information
for
the Marantz Model PM243/143 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 in-
cluded for parts which can be obtained locally.
2. FUNCTION OF EACH PART:
(1)
TREBLE/BASS/MIDDLE
SWITCH
By
using
the
loudness
circuit
and
setting
the
tap
position
on
sch
VR
to
70%,
100
Hz
and
10
kHz
are
boosted.
A
TR
1. P.W. BOARDS|
As can be seen from the circuit diagram the chassis of
Model PM243/143 consists of the following units. Each
unit mounted on a printed circuit board is discribed within
the square enclosed by a bold dotted line on the circuit
diagram. :
4. Main Amp ......... mounted on P.W. Board P700
2. Power Switch....... mounted on P.W. Board PGOO
3. Indicator.......... mounted on P.W. Board PSOO
4. 16P Connector ...... mounted on P.W. Board PVQOO
5. 6P Connector....... mounted on P.W. Board PV50
impedance
element
is
inserted
in
the
NF
lines
of
the
main
arenes
to
achieve
boosting
of
the
middle
range.
|
100 Hz +6 dB, 1 kHz +4 dB, 10 kHz +3 dB.
(2) POWER AMPLIFIER
_For voltage amplifier, monolithic IC uPC1270H | covering as far as the driving step is used; and for. the final step,
a
discrete
transistor
ts
used,
making
up
the
power
amplifier.
No
idling
adjustment
is
required;
if it is
needed
according
to
varistor diode’
s
rank,
it is
done
by
changing
the serial
resistance.
The
0
rank is
used for
this
unit.
(3) MUTING/LIMITER
Muting
is
enabled
when
the
power
is
turned
ON/OFF
by
controlling
the
voltage
at
pin
2
of
uPC1270H
(the
+
side
sf
the
front
step)
with
OQNO1
—
OQNO3.
An
abnormal
voltage
caused
by
short-circuiting
of
the
speaker
system,
etc.,
detected
by
QNO6
and
ONO7
so
that
the
above
muting
circuit
is
driven
by
QNOS
and
ON10.
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