Akai AT-2650 User manual

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I.
iit.
IV.
VI.
Vil.
VII.
IX.
XI.
XI.
For
SECTION 1
SERVICE MANUAL
TABLE OF CONTENTS
TECHNICAL
DATA
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AM-2650
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OF
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MODEL
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MODEL
AM-2650
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PRINCIPAL
PARTS
LOCATION
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MODEL
AT-2650
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2.
MODEL
AM-2650
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9
OPERATING
PRINCIPLES
OF
QUADRATURE
DETECTION
SYSTEM
........-
20-0
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eres
10
OPERATING
PRINCIPLES
OF
PLL
CIRCUIT
EMPLOYED
IN
STEREO
DEMODULATION
CIRCUIT
..
2.0...
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12
1.
PLL
CIRCUIT
OPERATION
.......
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12
2,
STEREO
DEMODULATION
CIRCUIT
2.2...
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13
OPERATING
PRINCIPLES
OF
FM
NOISE
CANCELLER
CIRCUIT
....
2.2...
0.
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15
1.
BASIC
CIRCUIT
FOR
PULSE
NOISE
SUPPRESSION
........
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15
2.
OPERATION
PRINCIPLE
WITH
STEREO
SIGNALS
..
0.0...
0.2
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15
3.
ADJUSTMENT
METHOD
FOR
THE
PILOT
SIGNAL
GENERATING
CIRCUIT
.......------
16
LEVEL
DIAGRAM...
0...
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ES
17
TUNER
ADJUSTMENT
(AT-2650)
2.00
en
ee
18
1.
FM
TUNER
SECTION
ADJUSTMENT
..
0.0.
0
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19
2,
AM
TUNER
SECTION
ADJUSTMENT
...
2.2.00
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20
AMPLIFIER
ADJUSTMENT
(AM-2650)
200.6
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21
1.
IDLING
CURRENT
ADJUSTMENT
.......
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21
2,
LEVEL
METER
INDICATION
ADJUSTMENT
...
2.2.0.0.
6-2
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es
22
TUNING
CORD
THREADING
...
2.1.
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nee
23
CLASSIFICATION
OF
VARIOUS
P.C
BOARDS
...
2.0...
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24
1.
P.C
BOARD
TITLE
AND
IDENTIFICATION
NUMBER
.....
22...
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25
2.
MODEL
AT-2650
COMPOSITION
OF
VARIOUS
P.C
BOARDS
.......
2.
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28
3,
MODEL
AM-2650
COMPOSITION
OF
VARIOUS
P.C
BOARDS...
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52
SCHEMATIC DIAGRAM
basic
adjustments,
measuring
methods,
and
operating
principles,
refer
to
GENERAL
TECHNICAL
MANUAL.

I. TECHNICAL DATA
1. MODEL AT-2650
FM TUNER SECTION
FREQUENCY RANGE
87.5 MHz to 108 MHz
SENSITIVITY (IHF) 1.6 UV
CAPTURE RATIO 1.2 dB
SELECTIVITY (IHF) More than 80 dB
IMAGE REJECTION
More than 110 dB (98 MHz)
IF REJECTION
More than 110 dB (98 MHz)
SPURIOUS REJECTION
More than 110 dB (98 MHz)
AM SUPPRESSION 55 dB
SIGNAL TO NOISE RATIO 75 dB
HARMONIC DISTORTION MONO Less than 0.1% (100% modulation)
STEREO
Less than 0.15% (100% modulation)
FM STEREO FREQUENCY RESPONSE
20 Hz to 15 kHz +1 dB, —3 dB
MUTING
Level Control (1 #V to 100uV)/Switchable to ON-OFF
STEREO SEPARATION
More than 45 dB (1 kHz)
SUB CARRIER SUPPRESSION
More than 65 dB
OUTPUT VOLTAGE
Controllable from 0 mV to 2V (100% modulation)
ANTENNA INPUT IMPEDANCE
300 ohms balanced, 75 ohms unbalanced
AM TUNER SECTION
FREQUENCY RANGE 520 kHz to 1,605 kHz
SENSITIVITY
(IHF)
80
uV/m
(bar
antenna),
13
uV
(external
antenna)
SELECTIVITY
(IHF)
More
than
30
dB
IMAGE REJECTION
More than 80 dB (1,000 kHz) _
IF REJECTION
More than 70 dB
SIGNAL TO NOISE RATIO
More than 50 dB
OUTPUT VOLTAGE _|_ Controllable from 0 mV to 2V
ANTENNA Built-in ferrite bar antenna
MISCELLENEOUS
SEMICONDUCTORS
| Transistors: 12, Diodes: 15, FETs: 3. 1Cs: 5
POWER REQUIREMENTS
120V, 60 Hz for U.S.A. and Canada
220V, 50 Hz for Europe except UK and Australia
240V, 50 Hz for UK and Australia
110V/220V/240V. 50/60 Hz internally switchable for other
countries.
DIMENSIONS
440 (W) x 144 (H) x 368 (D) mm, (17.3 x 5.7.x 14.5”)
WEIGHT
1
1 7.5 kg (16.5 lbs)
*
For
improvement
purposes,
specifications
and
design
are
subject
to
change
without
notice.
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i
2. MODEL AM-2650
POWER AMPLIFIER SECTION
RATED OUTPUT POWER
2-CHANNELS DRIVEN
65
watts
per
channel,
minimum
RMS,
at
8
ohms
from
20
to
20,000
Hz
with
no
more
than
0.08%
total
harmonic
distortion
POWER BANDWIDTH (IHF)
6 Hz to 60 kHz / 8 ohms (Total Harmonic Distortion: 0.08%)
6 Hz to 60 kHz/8 ohms (Total Harmonic Distortion: 0.08%)
SIGNAL TO NOISE RATIO (IHF) PHONO
Better than 75 dB
AUX | Better than 95 dB
RESIDUAL
NOISE
Less
than
0.5
mV
at
8
ohms
CHANNEL
SEPARATION
(IHF)
PHONO
Better
than
$5
dB
at
1,000
Hz
DAMPING
FACTOR
More
than
30
(1
kHz,
8
ohms)
OUTPUT
SPEAKERS
A,
B
(4
to
16
ohms)/A+B
(8
to
16
ohms)
HEADPHONE 4 to 16 ohms
PREAMPLIFIER SECTION
INPUT SENSITIVITY/IMPEDANCE
PHONO PHONO 1: 3 mV/33/47/100 kohms
PHONO 2: 3 mV/47 kohms
AUX 150 mV/100 kohms
TUNER 150 mV/100 kohms
TAPE
MONITOR
PIN:
150
mV/100
kohms,
DIN:
150
mV/100
kohms
OUTPUT LEVEL/IMPEDANCE
TAPE REC PIN: 150 mV/1 kohms, DIN: 30 mV/30 kohms
FREQUENCY RESPONSE
PHONO (RIAA EQUALIZATION)
TUNER, AUX, TAPE MONITOR
30 Hz to 15 kHz +1 dB, —1 dB
10 Hz to 60 kHz +1 dB, —1 dB
TONE CONTROL BASS +9 dB at 100 Hz
TREBLE +9 dB at 10 kHz
LOUDNESS
CONTROL
|
+10
dB
at
100
Hz,
+5
dB
at
10
kHz
(Volume control set at —30 dB position)
FILTER HIGH —3 dB at 10 kHz
LOW —3 dB at 30 Hz
AUDIO MUTE —20 dB attenuation
MISCELLANEOUS
SEMICONDUCTORS
Transistors:
33,
Diodes:
17,
ICs:
4
POWER
REQUIREMENTS
|
120V,
60
Hz
for
U.S.A.
and
Canada
220V. 50 Hz for Europe except UK and Australia
240V, 50 Hz for UK and Australia
110V/220V/240V, internally switchable, 50/60 Hz for other
countries.
DIMENSIONS
440
(W)
x
144
(H)
x
345
(D)
mm,
(17.3
x
5.7
x
13.6”)
WEIGHT
10.9
kg
(23.5
Ibs)
*
For
improvement
purposes,
specifications
and
design
are
subject
to
change
without
notice.

Ht. DISMANTLING OF UNIT
1. MODEL AT-2650 In case of trouble, etc. necessitating dismantling, please dismantle in the order
shown in the photographs. Reassemble in reverse order.
j 5
SCREW & KNOBS
SCREWS
Ww
On
SCREWS
UPPER COVER
SCREWS
i
FRONT : PaxtL SCREWS.
2
tt mare
f
Eee Ee at
yer ee og
e
@
1
| } |
| :
Ben, —e |
TRALEE it “ita
<__TUSRAENUURULETTATU RUE
BOTTOM Pi.ATE

2. MODEL AM-2650
Ht
iL iE
m Ce ae a ee aces
TUES ALLL LL
wey, TN ILUELNUNLG incHELIDALI HL
_& eee a e _ JS
d BOTTOM PLATE e
SCREWS
1 5
4A & Cc
| i
a \
NS
J * Gti
AKAL : ¢ { { { {
D E F
SCREWS CONTROL KNOBS
|
2 16
SCREWS
|
S | 7
BEPERCEUVER
|
i
|
i
|
|
'
SCREWS
Ly SCREWS.
FRONT PANEL
4 ° 8
wa

ili, CONTROLS
1. MODEL AT-2650
AEALT cai an svenco Tunes moan AT- 2660
© 2) ©
|
(9) GQ)
“900A BALAES ~ 98 BET OPEN!
‘SACU BE LOR - ME NS ERE /
seabenanceetae ~ mace OE |
pa cides ae ee ARON>O©
WNHAARWN>
Fig. 1 Controls AT-2650
FM DIAL SCALE
AM DIAL SCALE
SIGNAL STRENGTH METER
FM TUNING METER
POWER INDICATOR LAMP
FM STEREO INDICATOR LAMP
TUNING KNOB
POWER SWITCH
OUTPUT LEVEL CONTROL
NOISE CANCEL SWITCH
FM MUTE SWITCH and LEVEL ADJUSTER
INPUT SELECTOR
ANTENNA TERMINALS
AM FERRITE BAR ANTENNA
OUTPUT TERMINALS

2. MODEL AM-2650
OMNDGRYN>
ee ee ee ee
go RaON>O
aid tains Mobs ceca
i
‘E14 f
ee oe
POWER PHONES FILTER roue ease TREBLE
TAPE MONITOR:
SOURCE
Py a 4g ter tp
ea es er ;
ps)
@
q
f
f
-
is
Ns
a
_
. -E = ade 2 Ei ee cae i
AK AL erento miccn are AMPLRER moan! AM-2850
— i | i
i
|
| |
i
— | |
®
©
OU®
©
(8)
G
—SPEAKER Ao B (4-ehme)
Aend 8 (8-wotans)
canyen
* dn cese of une gutside Of indicated |
+ SROCK HAZARD 00 WAT TREKS
RISREE HK SBE - WE PAS SRLEVEE !
“SeRMETERESoATANR ~ 9x00 OFFA!
Fig. 2 Controls AM-2650
SPEAKER SYSTEM SELECTOR 16. TAPE MONITOR SWITCH
OUTPUT POWER LEVEL METERS (Left and Right) 17. IMPEDANCE SWITCH
AUDIO MUTE SWITCH 18. PHONO 1 TERMINALS
MODE SWITCH 19. PHONO 2 TERMINALS
LOUDNESS SWiTCH 20. TUNER TERMINALS
VOLUME CONTROL 21.. AUX TERMINALS
INPUT SELECTOR 22. Aand B SYSTEM SPEAKER TERMINALS
POWER SWITCH and POWER INDICATOR LAMP 23. EXTRA AC OUTLETS (some models not equipped
HEADPHONE JACK with this facility)
LOW FILTER SWITCH 24. GROUND TERMINAL
HIGH FILTER SWITCH 25, TAPE 1 SYSTEM DIN JACK
TONE SWITCH 26. TAPE 1 SYSTEM REC JACKS
BASS TONE CONTROL 27. TAPE 1 SYSTEM PLAY JACKS
. TREBLE TONE CONTROL 28. TAPE 2SYSTEM REC/PLAY JACKS
.
STEREO
BALANCE
CONTROL
29.
AC
CORD
(AC
Iniet
for
UK
and
some
other
countries)

IV. PRINCIPAL PARTS LOCATION
1. MODEL AT-2650
FRONT END BAR ANTENNA
FB824UI4 FILTER P.C BOARD ANT 901
T3-6501C
POWER TRANSFORMER
AT - 2650T -70
POWER SUPPLY P.C BOARD
T3- 4502
POWER SWITCH __
Sw}
TUNER PC BOARD
T3- 6501A
ti
Fig. 3 Top View
POWER INDICATOR
D2
rFM STEREO INDICATOR Di
; &
{
: ;
{oo
me ' Hl | ~
i i i
POWER SWITCH | | : TUNING SHAFT SELECTOR SWITCH
Sw | i i ! Swi
i |
OUTPUT LEVEL CONTROL ~ i i CMUTE LEVEL CONTROL
VR2 5SOKB | : VR3 2CKB
NOISE CANCEL SWITCH — “FM MUTE SWITCH
SW 3 swe
Fig. 4 Front View

2. MODEL AM-2650
WER TRA
a
BE
TR
NSr
Oe
MER
ELECTROLYTIC
CAPACITORS
risuiene:e
GARD
: 903,904 4000 52wv a
=
|
:
‘i
e202
|
lel
ea
M3-65014
: i
MAIN AMP PC BOARD
M3-E6504A
” 1
PEE.
MAIN VOL, & BALANCE P.C BOARD
M3-6502 A/B
Fig. 5 Top View
rAUDIO MUTE SWITCH SW3
;MODE SWITCH Sw!
i - LOUDNESS SWITCH SW2
| H
|
|
|
EA
L
KER SYSTEM ’ :
CTOR Ae ane LEFT RIGHT
m
|
H | |
‘ i
‘ ad : i
ee
per
es
Oe
i
ee
.
es
=
ob.
of.
of.
“
:
ot
See
|
i
{
LED PC BOARD
M3-6504C
1
1am
~
i:
i
pees
ean
“
a
S
cngeeels
woot
seat
i
4 i
Seerice
Si
ponte
ere
sis
betes
:
oiled
fia
=
POWER
SWITCH
|
Low
HiGH
=
|
i
|
i
'
SWw3O0!
sws
sw2
BASS
CONTROL
BALANCE
CONTROL
Sade ite | ! VRI SOKC VR2 250KMN
coe
|
|
TONE
SWITCH
TREBLE
CONTROL
TAPE
MONITOR
SWITCH
evel
:
sw}
VR2
S5SOKC
sw3
|
FILTE® SWITCH
Fig. 6 Front View