Marantz 2240 - Introduction; Service Notes; FM Front End Unit; AM Tuner Unit

Pearce ars Bak 4
INTRODUCTION
This service manual was prepared for use by Authorized Warranty Stations and contains
service information for Marantz Model 2240 Stereo-phonic Receiver.
Servicing information and voltage data included in this manual are intended for use by the
knowledgeable and experienced technician only. All instruction should be read carefully. No
attempt should be made to proceed without a good understanding of the operation in the
receiver.
The parts list furnish information by which replacement part may be ordered from the
Marantz Company. A simple description is included for parts which can be usually be obtained
through local suppliers.
1. SERVICE NOTES
As. can be seen from the circuit diagram the chassis of Model 2240 consists of the following
units. Each unit mounted on a printed circuit board is described within the square enclosed by a
bold dotted line on the circuit diagram.
1: (FMiFront Ends 0 ecb ee oa peed ie kaeee en ce teas Mounted on P.W. Board, P100
2iy ANIME THUR ceviseicte at iceltitear boca: Sats eater pice deviated echus ameteseueye Mounted on P.W. Board, P150
Si CRM =P a xvetie S osadwdinns oa0 0 witha Jented asad ie wie Mounted on P.W. Board, P200
Gis MP Xistediccsies astound ohh a hi BoraslaraPera de oid wana o3te. pdcetet Mounted on P.W. Board, P300
5. ANT-ATT. MutingUR......... 0.0.0 cece ee eee Mounted on P.W. Board, PU0Q1
6:. Dolby: Level vs. ciciices una 4 Hike oe See Bvrbine wield Wea WA Mounted on P.W. Board, PCO1
72 “PRONO:AMDP 42%. os aie Boel e eas, olen wae Sie ea ee as Mounted on P.W. Board, P400
83. {Dial Lamp iacteiice deectae hale @ hob we ek Sols erie eee es Mounted on P.W. Board, PZ01
9. Monitor, SW... . cc eee eee eee een Mounted on P.W. Board, PTO1
10. Function Lamp ........0.. 0. cee cece eee ee eee Mounted on P.W. Board, PY01
The. (Pre-TOme: Amps ie c2d os elaare. 8 «i dhe Sn ane ace eter ee SE Mounted on P.W. Board, PEO1
AZ “Filter SBeSW cs 5.55, ane, oie eis eek eae Cece Me, Bia avelalalonet wes Mounted on P.W. Board, PHO1
13: Power AMD e:aecad ee cee bb ae ew eee en eed eee e's Mounted on P.W. Board, P700
14. Power Supply «2.0... cee eee eee cece eee eee eens Mounted on P.W. Board, P800
2. AM TUNER
The AM TUNER postion of the 2240 is composed of one IC circuit (including RF
amplifier, local oscillator, mixer, IF amplifier, and detector) and three transistors. One of them
is a signal strength indication amplifier, while the other two are amplifiers for detected audio
signals.
All components except Tuning capacitor and ferrite bar antenna are mounted on a printed
circuit board P150.
The AM signals induced in a ferrite bar antenna are applied to the input of RF amplifier (pin
12)
and
amplified
to
the
level
required
for
overcoming
the
conversion
noises,
thus
giving
good
S/N performance. The tuned circuits inserted in both output and input circuit of RF amplifier
assure very high image and spurious rejection performance.
Thus amplified and selected AM signals are then applied to one input of Mixer section (pin
1}. While the local oscillator voltage is injected to the other input of the section (pin 16]
through a capacitor C157. Then both AM signals and oscillating voltage are mixed and
converted into 455 KHz intermediate frequency. The resulting IF signal is applied to the IF
transformer L153 consisting of one ceramic filter and two tuned circuits.
The
output
of
L153
is.led
to
the
IF
amplifier’s
input
(pin
9)
through
a
coupling
capacitor
C162
and
amplified
to
the
sufficient
level
to
drive
the
detector.
The
detected
audio
signa
derived
from
pin 7
is
filtered
and
amplified
and
final
audio
output
is
obtained
from
the
collector
of
H153
and
applied
to
the
TAPE
OUTPUT
jacks
through
the
function
switch.