McIntosh MA-2275 Service manual
TUBE
INTEGRATED AMPLIFIER
CONTENTS
Performance Specifications ........................................ 2
Notes ......................................................................... 2
Rear Panel .................................................................. 3
Section Location ........................................................ 4
Block Diagram ...................................................... 5 - 7
Interconnection Diagram .................................... 8 - 10
Main Schematic and PCB................................. 11 - 16
Control Schematic and PCB ............................. 17 - 20
Balanced Schematic and PCB ........................... 21 - 22
Volume/Tone Schematic and PCB ..................... 23 - 26
SERVICE MANUAL
Data Schematic and PCB................................... 27 - 28
Pushbutton Schematic and PCB ........................ 29 - 30
Amplifier Schematic and PCB............................ 31 - 34
Power Supply Schematic and PCB..................... 35 - 38
Meter Schematic and PCB ................................. 39 - 40
Backup PS Schematic and PCB ................................ 41
Terminal Schematic and PCB ................................... 42
Parts List ............................................................ 43 - 48
Exploded View and Parts List ............................. 49 - 52
Repacking Instructions ............................................. 53
PERFORMANCE SPECIFICATIONS
Power Output
Minimum sine wave continuous average power output per
channel, both channels operating is:
75 watts into a 2 ohm load
75 watts into a 4 ohm load
75 watts into an 8 ohm load
Rated Power Band
20Hz to 20,000Hz
Total Harmonic Distortion
Maximum Total Harmonic Distortion at any power level
from 250 milliwatts to rated power output is:
0.5% for a 2, 4 or 8 ohm load
Frequency Response
+0, -0.5dB from 20Hz to 20,000Hz
+0, -3dB from 10Hz to 50,000Hz
Sensitivity
Phono: 4.4mV for 2.5V preamp output
High Level: 450mV for 2.5V preamp output
Power Amplifier Input: 2.5V for rated output
A-Weighted Signal To Noise Ratio
Phono Input: 80dB below 10mV input
High Level: 97dB below rated output
Power Amplifier: 110dB below rated output
Intermodulation Distortion
Maximum Intermodulation Distortion if instantaneous
peak output does not exceed twice the rated output, for
any combination of frequencies from 20Hz to 20,000Hz is:
0.5% for a 2, 4 or 8 ohm load
Preamplifier Maximum Voltage Output
Phono: 8V
High Level: 8V
Main Out: 8V at preamp output
Voltage Gain
High Level to Tape output: 0dB
High Level to Preamp output: 15dB
Wide Band Damping Factor
Greater than 18
Power Requirements
100 Volts, 50/60Hz at 3.6 amps
110 Volts, 50/60Hz at 3.6 amps
120 Volts, 50/60Hz at 3.6 amps
220 Volts, 50/60Hz at 1.8 amps
230 Volts, 50/60Hz at 1.8 amps
240 Volts, 50/60Hz at 1.8 amps
Note: Refer to the rear panel of the MA2275 for the correct
voltage.
Preamplifier Tube Compliment
2 - 12AX7A Phono Circuitry
2 - 12AX7A High Level Circuitry
Power Amplifier Tube Compliment
2 - 12AT7
4 - KT88/6550
Overall Dimensions
Width is 17-3/4 inches (45.09cm), Height is 10-1/8 inches
(25.72cm) including feet, Depth is 18-3/4 inches (47.63cm)
including the Front Panel and Knobs
Input Impedance
Phono: 47k ohms, 65pF
High Level: 22k ohms
Maximum Input Signal
Phono: 90mV
High Level: 8V
1. The heavy lines on the schematic denote the primary
signal path.
2. Unless otherwise noted, all voltages indicated on the
schematics are measured under the following conditions:
a. AC input at 120 volts, 50/60Hz.
b. All voltages are +/-10% with respect to ground. A
high impedance (10 megaohm) voltmeter must be used.
3 . Unless otherwise specified:
a. Resistor values are in ohms.
b. Capacitor values are microfarads (uF).
c. Inductor values are in microhenries (uH).
Weight
77 pounds (35 kg) net, 110 pounds (50 kg) in shipping
carton
NO TES
4 . On PC board drawings, Square pad indicates:
a. Polarized Capacitors - Positive
b. Diodes - Cathode
c. Others - Pin 1
5. WARNING
Parts marked with the symbol have critical
characteristics. Use only replacement parts recommended by the manufacturer.
2
T OP AND REAR VIEWS
MA2275
CAUTION
RISKOF ELECTRIC SHOCK
DONOT OPEN
CAUTION
FORCONTINUED PROTECTION
AGAINSTFIRE HAZARD REPLACE ONLY WITH SAME
TYPEAND RATING FUSE.
120V 50/60Hz 3.6A
AVIS
RISQUEDE CHOC ELECTRIQUE - NE PAS
OUVRIR.REMPLACER PAR UN FUSIBLE DE MEME
TYPE,AMPERAGE ET VOLTAGE.
T 4AL250V
SLO-BLO
EXT SENSOR
POWER
AMP IN
R
L
POWER CONTROL
MAIN
OUTPUTS
PREAMP
12
ACC
INPUTS
DVD
TAPE
TAPE
SUM
TUNER
DATAPORTS
CD 2CD
PHONO
GND
CD INPUT
R
INTEGRATED AMPLIFIER
L
MA2275
McINTOSHLABORATORY, INC.,
BINGHAMTON,NY MADE IN USA
SERIAL
NUMBER
3
SECTION LOCATIONS
TOP VIEW WITH COVERS REMOVED
POWER
1
TRANSFORMER
OUTPUT
TRANSFORMER
METER
PCB
CONTROL
PCB
TERMINAL
PCB
AMP
PCB
1
3
DATA
PCB
6
BALANCED
PCB
4
12
13
8R 8L
OUTPUT
1
TRANSFORMER
VOLUME/TONE
510
PCB
PUSHBUTTON
7
PCB
TERMINAL
PCB
AMP
PCB
POWER SUPPLY
PCB
BACKUP POWER
SUPPLY PCB
11
MAIN
2
PCB
9
CHOKE
1
FILTER
BOTTOM VIEW WITH COVER REMOVED
4
BLOCK DIAGRAM
MA2275
5 76
1
INTERCONNECT
8 109
MA2275
2A
MAIN
049965 SH 1 OF 2
11 1312
2B
MAIN
049965 SH 2 OF 2
J6
129472
Rev. A
C13
C9
C86
R47
C44
R48
C77
U10
R43
C75
C60
C59
D1
C42
C73
R74
C85
U9
R21
C84
R15
C14
R22
R18
R17
U4
U2
K21
K1
C10
R16
D4
K20
J8
JMP1
C48C47
R53
R54
C49
R55
R79
R60
R63
R70
R69
C65
K18
C55
C54
C57
C63
U6
R83
C71 C69
R71
C62
R84
J4
C66
J10
R61
C64
K19
R81
Q1
R80
R88
R85
R82
R87
R94
R93
R91
C74
C82
C78
J7
R52
U7
D2
C80
C79
U11
C83
C81
GP2
R57
R58
R27
*
J11
C11
R19
C7
R11
C76
C3
C15
J1
C58
C41
R46
U5
GP1
R95
R23
R92
R86
R96
U1
C43
R5
R6
R25
K2
V5 V6
R13
R4
K3
K7
C5
R9
R2
C24
J2
C2
R31
C6
R10
*
V4
R1
R3
C1
C16
R26R34
C31
R41
R44
R35
C30
K6
K9
R32 R28
C26
C23
R14
R7
R8
R37
R36
C37
C35
C33
K8 K11
C25
C28
R20
R12
C4
U3
C40
C12
C8
J5
40
R
R39
C36
R45
C34
K10
C27
C18
R77
C32
R42
R38
C29
K13 K12
R29
C17
C50
R56
C53
C56
R62
R65R67
R33
C20
J3
R66
C67
C68
R59
C61
R64
U8
R78
R68
C38
C39
R49
K17
C19
C46
R90
R89
C51
K16
*
C52
*
V7
R75
R76
Q4
R73
R72
R24
Q2
R30
Q3
C45
C72 C70
R51
R50
14 1615
CD DVDPH CD2 TUNER TAPE
TAPE OUT 2 AMP INOUT 1
OUT
MA2275
3
CONTROL
049966
17 18
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