Akai AM 2450 Service Manual

Page 2

AT-2450

AM-2450

AKAI STEREO TUNER AND STEREO INTEGRATED AMPLIFIER

MODEL AT-2450 AM-MSO

ALSO APPLICABLE TO BLACK PANEL MODEL

SECTION 1 SERVICE MANUAL ...................... 1
SECTION 2 PARTS LIST ............................ 33
SECTION 3 SCHEMATIC DIAGRAM ................. 48

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The Quadrature Detection Circuit is comprised of a
Phase Circuit, a Multiplier Circuit and a Low Pass Filter
(L.P.F.) as shown in Fig. 7.

There are two types of Phase Circuits, the Single tuning
type shown in Fig 8 and the Double tuning type shown
in Fig. 9. However, because with the double tuning type
there is less frequency deviation in relation to carrier
frequency, linearity is improved as shown in Fig. 10 and
phase distortion is reduced, this type of phase circuit is
employed in the AT-2450.

Input signal 51 is divided into the part which enters the
direct multiplier circuit and the part which passes the
phase circuit and enters the multiplier circuit. The signal
supplied to the phase circuit is always 90° phase delayed
at Ll. Also because at Nonmodulation time, L2 is tuned
to 10.7 MHz, if modulation is applied and $1 is changed
from 10.7 MHz, phase deviation at L2 will take place
proportionately in relation to this change part and this
becomes 82 signal which is delayed in relation to SI.

At Non-modulation, because as shown in Fig. 11, the
input signal 81 and 90° phase delayed (by means of L1)
signal 82 are switched by means of the multiplier circuit,
the output signal becomes 53.

Because this S3 passes the low pas filter and becomes S4
fixed direct current, the detector output is zero. Then,
when modulation is applied, because the switched
output is varied according to the degree of modulation,
and the output which passed the lowe pass filter
becomes the pulsating current part as shown in Fig. 12,
detector output is obtained.

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AC INLET SYSTEM

This model is equipped with an AC INLET SYSTEM. Please refer to the AC INLET SYSTEM CHART below for the
specific type. By the AC INLET SYSTEM, AC (mains) cord can be connected to and disconnected from the model
because the model is provided with socket exclusively forAC (mains) cord on its main body.

Please note, however, thét certain models are not equipped with this system and has a built-in AC (mains) cord as

before.
AC INLET SYSTEM CHART
CLASS I CLASS 11

@ This mark indicating double insula-
tion will be attached to machines rear

panel
a
0
Picture 1
AC INLET
to be
installed

on machines

countries

Q Connects to
I/\/ machine's
/ AC inlet Most of the
Connects to Denmark European
machines Picture 2 countries
AC Inlet
AC (mains)
cord
Australia ' Australia
differs 32"de diifers according
'0 W3" 5" to wall socket
Parts List for AC (mains) Cord Set
Standard Description Type of AC Inlet Parts No.
CEE Cord Set CEE (3 cores) 3P EW302993
C1 I BEAB Cord Set BEAB (3 cores) 3P EW302994
5 SAA Cord Set SAA (3 cores) 31> EW302996
U/T Cord Set U/T (3 cores) 3P EW302646
CEE Cord Set CEE (2 cores) 2P EW638144
C1 II BEAB Cord Set BEAB (2 cores) 2P EW302995
5 SAA Cord Set SAA (2 cores) 2? EW302991
U/T Cord Set U/T (2 cores) 2P EW302899

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