Alto OEX400 Service Manual
Service Manual
Model: OEX-400
www.altoproaudio.com
Version: 1.2
CONTENT
1. Introduction.............................................................................................1
2. Specification............................................................................................2
3. Block Diagram.........................................................................................4
4. Schematic Diagram.................................................................................5
5. Wiring Diagram......................................................................................10
6. Printed Circuit Board..........................................................................11
7. Exploded View & Mechanical Parts List..................................................14
8. Electrical Parts List.............................................................................19
1. Introduction
Trolley appearance
2 (two-SPEAKER) + 1 (7-channel mixer super combination)
One-way full-range speaker system
4 XLR MIC input with ultra low noise microphone pre-amplifiers and PHANTOM power+48V
1 stereo LINE input
Warm, natural 2-band EQ for each channel
Precision level control
24-bit DSP effects with powerful algorithms (16 presets)
Extremely high headroom offering excellent dynamic range
Plastic reinforced cabinet (polypropilene)
350W (EIAJ) of Power
Two 10m speaker cables
Two folding speaker
Compartment for store following accessories:
Accessory List:
Folding speaker 2 10"
Power cord 1 IEC power cord
Customized Speaker Cable 2 10m
MIC 2 5m
- 1 -
2.Technical Specification
Mixer Section
- 2 -
Speaker Section
Power Section
Physical
- 3 -
3. Block Diagram
D
C
CH INPUT
(CH1~3)
BAL/UNBAL
CH INPUT
CH4/5
BAL/UNBAL
1
X1-3A
X1-3B
T
R
S
XLR&TRS
X9
XLR
X4
LEFT(MONO)
X5
RIGHT
XLR&TRS
2
3
4
5
6
7
8
LOW HI
X13
X1
X2
X3
2-STAGE EQ
MIAN-BUS
LEVEL
5
6
4
3
2
1
1
2
3
4
5
2
3
1
LOW HI
2-STAGE EQ
DSP/FX AUX1 POST
DFX(DSP)
63HZ
400HZ
160HZ
2.5K
1K
16K
6.3K
POWER MODEII
RMS 300W
7-STAGE EQ
J13
4
3
2
LOW BOOST
MAIN LEVEL
MONITOR LEVEL
MASTER METER
1
CON4
POWER_CONNECT
+22V
-22V
POWER SUPPLY
OEX-400_MIXER
LEVEL
4
5
2
3
1
DSP/FX AUX1 POST
MONITOR METER
R
T
S
MASTER SPK OUT1
X14
R
T
S
MASTER SPK OUT2
R
T
X4
S
MONITOR OUT
STEREO OUTPUT
D
+15V
+5V
-15V
C
CH6/7
STEREO INPUT
B
A
TAPE INTAPE OUT
X6
AUX RETURN
X8
STEREO UNBAL INPUT
PRESETS
LOW HI
R
T
2-STAGE EQ
LEVEL
X5
S
PHONES OUT
STEREO OUTPUT
B
DSP/FX AUX1 POST
R
T
X7
S
FX SEND
4
5
2
3
1
AUX RETURN LEVEL
DSP BOARD
MAIN-BUS
DFX(DSP)
R
T
X6
S
FOOTSWITCH
A
MUTE
DSP FOOT
1
2
3
4
5
6
7 8
- 4 -
4. Schematic Diagram
X1A
XLR&TRS
X1
X2
X3
D
CH1 XLR INPUT
CH1 TRS INPUT
T
R
S
XLR&TRS
X1B
X2A
XLR&TRS
CH2 XLR INPUT
C
CH2 TRS INPUT
T
R
S
XLR&TRS
X2B
X3A
XLR&TRS
CH3 XLR INPUT
CH3 TRS INPUT
T
R
B
A
S
XLR&TRS
X3B
5
6
4
3
2
1
X1
X2
X3
5
6
4
3
2
1
X1
X2
X3
5
6
4
3
2
1
CN500
1 2
3 4
5 6
7 8
9 10
11 12
13 14
15 16
17 18
19 20
21 22
23 24
25 26
HEADER 13X2
+30VCC
-30VCC
CN500 connect to POWERMODEII
CN501 connect to J14(SCH5)
C3
47u/25V
C4
47u/25V
C1
47u/25V
C2
47u/25V
C13
47u/25V
C15
47u/25V
C11
47u/25V
C12
47u/25V
C14
47u/25V
C27
47u/25V
C25
47u/25V
C26
47u/25V
R1
3K9
R2
3K9
R19
22K
R20
22K
R6
3K9
R7
3K9
R23
22K
R24
22K
R8
3K9
R12
3K9
R27
22K
R28
22K
R500
33R 5W
R501
47R 5W
+22VCC
-22VCC
J17
CON2
CN501
1
2
3
CON3
S1
SW SL2020
R163
22K
C146
47u/25V
1
2
CH1CH1+
CH2CH2+
J6
1
2
3
4
5
6
7
8
9
10
CON10
J8
CON12
12
11
10
9
8
7
6
5
4
3
2
1
12
11
10
9
8
7
6
5
4
3
2
1
J9
CON12
J7
10
CON10
R252
22K
1
2
3
4
5
6
7
8
9
MO-OUT-L
MO-OUT-R
HP-OUT-L
HP-OUT-R
FOOTSW
EFFECT-IN
AUX-RETURN-L
AUX-RETURN-R
C31
47u/25V
47u/25V
C64
22P
R54
10K
C67
22P
C32
C65
2
3
C68
2
3
2
3
100P
R51
R50
10K
R55
R56
22P
U1A
4580M
22P
U3A
4580M
U5A
4580M
C72
22P
10K
10K
10K
C69
22P
R61
10K
R154
120R
C193
100PC192
47u/25V
1
47u/25V
1
47u/25V
1
4
5
2
3
1
4
5
2
3
1
4
5
2
3
1
4
5
2
3
1
4
5
2
3
1
C5
R52
10K
C16
R57
10K
C17
R58
10K
X4
SCJ-0658-1-Y
X5
SCJ-0658-1-Y
X6
SCJ-0658-1-Y
X7
SCJ-0658-1-Y
X8
SCJ-0658-1-Y
6
5
6
5
6
5
R91
12K
C66
22P
U1B
4580M
R21
22K
R93
12K
C70
22P
U3B
4580M
R25
22K
R94
12K
C71
22P
U5B
4580M
R29
22K
T
MOINTOR OUT
R
S
T
HEADPHONE OUT
R
S
T
FOOTSW
R
S
T
FX SEND
R
S
T
AUX RETURN
R
S
C6
47u/25V
7
C18
47u/25V
7
C28
47u/25V
7
R3
3K9
EQ HI
10KHZ
LO
100HZ
R100
8K2
R9
3K9
EQ HI
10KHZ
LO
100HZ
R104
8K2
R10
3K9
EQ HI
10KHZ
LO
100HZ
R109
8K2
MAIN SECTION
OEX-400_2.SCH
VR1
B50K
R101
8K2
VR2
B50K
VR5
B50K
R105
8K2
VR6
B50K
VR9
B50K
R110
8K2
VR10
B50K
2
2
2
2
2
2
C82
4N7(M)
C87
4N7(M)
C83
4N7(M)
C88
4N7(M)
C84
4N7(M)
C89
4N7(M)
13
R4
3K9
R102
8K2
13
13
R5
3K9
R106
8K2
13
13
R11
3K9
R111
8K2
13
-VCC1
C120
0.1u
C126
+VCC1
0.1u
DSP SECTION
OEX-400_3.SCH
8 4
C7
47u/25V
C19
47u/25V
C20
47u/25V
-VCC
U1C
4580M
+VCC
7 BAND EQ
OEX-400_4.SCH
R138
10
R141
10
2
3
2
3
2
3
4580M
C92
4.7u/50V
4580M
C93
4.7u/50V
4580M
C94
4.7u/50V
8 4
U2C
4580M
U2A
U4A
U6A
C100
22P
47u/25V
C101
22P
47u/25V
C103
22P
47u/25V
C121
0.1u
C127
0.1u
R124
1M
1
C8
1 3
R22
22K
R125
1M
1
C21
1 3
R26
22K
R126
1M
1
C29
1 3
R30
22K
+VCC
POWER&DSP
OEX-400_5.SCH
47u/25V
47u/25V
47u/25V
-VCC
C9
C22
C23
2
2
2
VR3
W50K
VR7
W50K
VR11
W50K
R139
10
R142
10
R143
10
R103
8K2
U2B
4580M
J1
R107
8K2
U4B
4580M
J2
R108
8K2
U6B
4580M
J3
R140
10
C33
4.7u/63V NP
6
5
6
5
6
5
C102
22P
PRE/POST
C104
22P
PRE/POST
C105
22P
PRE/POST
-VCC3
-VCC2
+VCC3
+VCC2
R132
36K
7
C10
47u/25V
R133
36K
7
C24
47u/25V
R134
36K
7
C30
47u/25V
R92
20K
R95
20K
R96
20K
C122
0.1u
C123
0.1u
C128
0.1u
C129
0.1u
2
2
2
4580M
4580M
R53
10K
R59
10K
R60
10K
8 4
U3C
8 4
U5C
VR4
W50K
1 3
VR8
W50K
1 3
VR12
W50K
1 3
-VCC2
+VCC2
-VCC3
+VCC3
87654321
4580M
4580M
MAIN-BUS
FX-SEND
MAIN-BUS
FX-SEND
MAIN-BUS
FX-SEND
8 4
U4C
8 4
U6C
D
C
B
C124
0.1u
C125
0.1u
C130
0.1u
C131
0.1u
A
1 2 3 4 5 6 7 8
- 5 -
D
C
B
A
X9
XLR-M
X10
T
R
S
SCJ-0658-1-Y
X11
SCJ-0658-1-Y
X12
UNBAL-4P
-VCC
R144
10
R145
10
+VCC
TAPE-IN
TAPE INTAPE OUT
4580M
1
2
3
4
5
2
3
1
4
5
2
3
1
LCH IN
RCH IN
8 4
U7C
C194
100P
-VCC4
+VCC4
C43
47u/25V
C42
47u/25V
C44
47u/25V
C50
47u/25V
C52
47u/25V
C51
47u/25V
C132
0.1u
C133
0.1u
4580M
CH4/5-IN
R164
12K
2
3
R15
3K9
R16
3K9
R37
22K
R38
22K
R39
22K
R40
22K
C195
100P
8 4
U8C
U10A
4580M
47u/25V
47u/25V
C74
22P
C53
C54
C134
0.1u
C135
0.1u
6
5
47u/25V
1
R74
22K
R75
22K
R170
R171
4580M
R97
12K
C45
U8B
4580M
8 4
U9C
2.2K
2.2K
R33
22K
C73
22P
47u/25V
7
R31
22K
TAPE IN
TAPE OUT
C136
0.1u
C137
0.1u
C34
J10
1
2
3
4
5
6
7
8
9
10
11
12
CON12
R13
3K9
EQ HI
10KHZ
LO
100HZ
R112
8K2
R17
3K9
EQ HI
10KHZ
LO
100HZ
R117
8K2
J11
1
2
3
4
5
6
7
8
9
10
11
12
CON12
VR13
B50K
R113
8K2
VR14
B50K
VR17
B50K
R118
8K2
VR18
B50K
2
2
2
2
C85
4N7(M)
C90
4N7(M)
C86
4N7(M)
C91
4N7(M)
TAPE-OUT
13
13
13
13
TAPE-IN
R14
3K9
R18
3K9
R114
8K2
R119
8K2
2
3
2
3
6
5
U8A
4580M
U7A
4580M
U7B
4580M
C35
47u/25V
C46
47u/25V
2
3
2
3
4.7u/50V
R66
10K
C75
22P
1
R67
10K
C78
22P
R76
10K
C76
22P
1
R78
10K
C79
22P
R77
10K
C77
22P
7
R81
10K
C80
22P
4580M
C95
4.7u/50V
4580M
C96
47u/25V
C98
47u/25V
U9A
U11A
C97
C99
47u/25V
4580M
C106
22P
C111
22P
R127
1
47u/25V
R128
1
47u/25V
R68
10K
R80
20K
R79
20K
8 4
U13C
1M
C36
1M
C47
CH4/5-IN
C144
0.1u
C145
0.1u
R32
22K
R62
10K
R34
22K
R69
10K
J4
J5
J12
CON4
-VCC
+VCC
47u/25V
1 3
PRE/POST
47u/25V
1 3
PRE/POST
1
2
3
4
C37
2
C38
2
R146
10
R147
10
VR15
W50K
VR19
W50K
R115
8K2
R116
8K2
R99
20K
U9B
4580M
U11B
4580M
4
5
2
3
1
6
5
6
5
X13
SCJ-0658-1-Y
C107
22P
R98
20K
C108
22P
VR20
2
W50K
1 3
T
R
S
OUT1
X14
4
5
2
3
1
SCJ-0658-1-Y
OUT2
X15
4
5
2
3
1
SCJ-0658-1-Y
AMP MO OUT----NC
-VCC5
C138
0.1u
8 4
U10C
4580M
+VCC5
C139
0.1u
8 4
U11C
4580M
R135
36K
7
R136
36K
7
FX-SEND
C39
47u/25V
C48
47u/25V
C140
0.1u
C141
0.1u
2
R70
10K
-VCC1
8 4
+VCC1
R63
10K
MAIN-BUS
U12C
4580M
1 3
VR16
W50K
C142
0.1u
C143
0.1u
MAIN-BUS
FX-SEND
R35
22K
R71
10K
R36
22K
87654321
C109
22P
R161
62K
2
3
U12A
4580M
C112
22P
R165
2K2
2
3
U13A
4580M
C40
1
47u/25V
R168
1
10k
C113
6
5
U12B
4580M
R72
10K
C196
1N5
22P
R64
10K
R73
10K
7
C49
47u/25V
1
6
5
C110
22P
6
5
C114
22P
R162
10K
U13B
4580M
MAIN-IN-EQ
R65
18K
U14B
4580M
C41
7
EFFECT-IN
47u/25V
2
U14A
4580M
3
7
DSP-IN
D
C
B
A
1 2 3 4 5 6 7 8
- 6 -
87654321
R262
15.0K
CI00185
C238
100nF
6
5
R265
12.0K
R264
27.0K
4580M
U10B
7
C239
47u/25V
R248
1K
R249
10K NC
R254
4.7K
TO AMP IN
J13
4
3
2
1
CON4
R253
4.7K
D
C
C115
22P
R41
22K
6
5
R155
120R
R247
10K
R156
120R
C198
10P
R172
5K6
Q1
PNP
1N4148
D2
Q2
PNP
R175
6K8
E2C
E2C
MAIN-IN-EQ
D
MN-EQ-OOL-1
+VCC6
C
1N4148
D1
R178
39K
1
1
7
B
R191
470R
R192
470R
B
2
3
U23A
4580M
MN-EQ-OOL-2
U15B
4580M
3
+VCC6
LM339
U21A
3 12
R194
43R
3 12
3
5
5
2
4
4
2
1
2
3
GR
D10
U22A
LM339
C197
10P
-VCC6
-VCC6+VCC6
MN-EQ-SOURCE
R42
R176
22K
6K8
R177
39K
1
7
6
R195
510R
7
6
D12
1
GR
1
GR
D11
U21B
LM339
U22B
LM339
2
3
U15A
4580M
R196
1.2K
D13
GR
C116
22P
U16A
4580M
9
9
R173
5K6
C55
47u/25V
1
R184
680R
1 3
VR21
W50K
R120
8K2
2
R189
2K7
C117
22P
R43
22K
6
5
U16B
4580M
C56
7
47u/25V R44
22K
C237
0.22u/50V
MASTER(VOLUMES)
TAPE-OUT
+10DB0DB-10DB-30DB
1
D19
4148
7
D22
4148
D20
4148
U20A
4580M
D21
4148
U20B
4580M
R199
100K
R202
100K
R200
2
100K
3
MN VMETER
MO VMETER
R201
6
100K
5
D17
RED
-VCC6
R82
10K
+VCC6
R83
10K
-VCC6
C57
47u/25V
47u/25V
C60
14
YE
D14
U21C
LM339
8
8
U22C
LM339
14
R197
2.7K
D15
YE
13
RED
D16
U21D
LM339
11
10
R198
22K
11
10
U22D
LM339
13
+10DB0DB-10DB-30DB
R84
10K
4580M
R213
8K2
8 4
U20C
2
3
6
5
4580M
-VCC6
+VCC6
4580M
U17B
C152
0.1u
C153
0.1u
C81
22P
U17A
47u/25V
R137
36K
47u/25V
1
7
C61
C59
C190
47UF/25V
C191
47UF/25V
C58
B
R207
27K
47u/25V
VR22
2
W50K
1 3
MONITOR OUT
R255
27K
R255 IS NOT USED
-VCC
R148
A
10
R149
10
+VCC
1 2 3 4 5 6 7 8
R46
22K
MO-OUT-L
C118
22P
R217
10K0
R214
100R 1/4W
R45
22K
C119
22P
R216
10K0
R215
100R 1/4W
MO-OUT-R
2
3
2
3
U18A
BA15218N
U19A
BA15218N
6
1
5
6
1
5
U18B
BA15218N
U19B
BA15218N
7
7
R157
120R
R158
120R
R159
120R
R160
120R
HP-OUT-L
HP-OUT-R
4580M
8 4
U14C
-VCC1
+VCC1
C166
0.1u
C167
0.1u
8 4
U15C
4580M
-VCC8
+VCC8
C168
0.1u
C169
0.1u
4580M
8 4
U16C
R151
10
-VCC
+VCC
R150
10
C170
0.1u
C171
0.1u
4580M
8 4
U17C
C172
0.1u
C173
0.1u
4580M
8 4
U18C
C174
0.1u
C175
0.1u
4580M
8 4
U19C
C164
0.1u
C165
0.1u
C188
47UF/25V
C189
47UF/25V
B
A
- 7 -
87654321
D
C
MN-EQ-OOL-1
MN-EQ-OOL-2
MN-EQ-OOL-1
MN-EQ-OOL-2
63HZ FREQUENCY BAND
13
R218
18K
2
W100K
VR24A
46
5
W100K
VR24B
7
U23B
4580V
C200
220N
R225
15K
5
6
160HZ FREQUENCY BAND
13
R221
18K
2
W100K
VR25A
46
5
W100K
VR25B
1
U24A
4580V
C202
220N
R121
8K2
3
2
R226
15K
R122
8K2
220N
C199
220N
C201
R227
15K
R174
5K6
R123
8K2
R232
1K2
MN-EQ-SOURCE
MN-EQ-SOURCE
MN-EQ-OOL-1
MN-EQ-OOL-2
MN-EQ-OOL-1
MN-EQ-OOL-2
1KHZ FREQUENCY BAND
13
R219
18K
2
W100K
VR27A
46
5
W100K
VR27B
1
U25A
4580V
C205
10N
R229
47K
3
2
2.5KHZ FREQUENCY BAND
13
R222
18K
2
W100K
VR28A
46
5
W100K
VR28B
7
U25B
4580V
C207
10N
R47
22K
5
6
R230
47K
R48
22K
10N
C204
10N
C206
R231
47K
R190
2K7
R49
22K
R233
1K
MN-EQ-SOURCE
MN-EQ-SOURCE
MN-EQ-OOL-1
MN-EQ-OOL-2
W100K
VR30B
-VCC
+VCC
R152
10
R263
0R 1/4W
R153
10
16KHZ FREQUENCY BAND
13
46
W100K
VR30A
4580V
2
5
8 4
U23C
R220
18K
-VCC8
+VCC8
C176
0.1u
C180
0.1u
7
U26B
4580V
C209
1N
4580V
8 4
U24C
R208
27K
5
6
C177
0.1u
C181
0.1u
R209
27K
4580V
1N
C208
8 4
U25C
R210
27K
R166
2K2
C178
0.1u
C182
0.1u
4580V
MN-EQ-SOURCE
8 4
U26C
C179
0.1u
C183
0.1u
D
C
B
A
MN-EQ-OOL-1
MN-EQ-OOL-2
400HZ FREQUENCY BAND
13
R223
18K
2
W100K
VR26A
46
5
W100K
VR26B
1 2 3 4 5 6 7 8
7
U24B
4580V
C212
33N
R179
39K
5
6
R180
39K
33N
C213
R181
39K
R234
1K8
MN-EQ-SOURCE
MN-EQ-OOL-1
MN-EQ-OOL-2
6.3KHZ FREQUENCY BAND
13
R224
18K
2
W100K
VR29A
46
5
W100K
VR29B
1
U26A
4580V
C210
1N
R203
100K
3
2
R204
100K
1N
C211
R205
100K
R235
3K3
MN-EQ-SOURCE
B
A
- 8 -
87654321
D23
1N4002
R211
R85
R86
27K
10K
27K
10K
+VCC
-VCC
C214
56P
C63
47u/25V
R182
39K
2
3
D3
1N4148
U27A
4580M
R236
10R
R87
10K
R183
39K
C215
3N3R212
2K2
D4
1N4148
D5
1N4148
TR1
J176
331
15K
2
2
VR23
W50K
R237
56K
R242
2
12K
1 3
+5V
MAIN-BUS
J14
3
2
1
CON3
R228
1
CN1
C62
1
47u/25V R167
MUTE
6
5
U27B
4580M
7
AUX-RETURN-R
D
C
DSP-OUT-R
AUX-RETURN-L
DSP-OUT-L
U31A
74HC14
U31B
74HC14
U31C
74HC14
12
34
56
HEADER 8X2
D28
1N4148
DSP-IN
R129
1M
C203
220N
D29
1N4148
5
U29A
6
Q
7
B
A
Q
1
FX-CLIP
SD
CLK
CD
J
K
2
4
3
74HC109
1
U28A
LM393
+VCC
3
2
C223
100N
R88
10K
R130
1M
R244
2M2
7
U28B
LM393
5
6
R206
7.5K
R193
470R
-VCC
R245
820K
R251
2K
DSP-IN
D6
1N4148
D8
1N4148
R250
1K
DSP-OUT-L
DSP-OUT-R
D7
1N4148
D9
1N4148
R131
1M
+5V
10
+5V
8
3
Q
DIS
THR
Q
Q
VCC
GND
1
11
SD
CLK
CD
15
TRIG
CVolt
J
K
U29B
74HC109
7
6
9
R
U30
NE555
14
12
13
12
34
56
78
910
1112
1314
1516
4
2
5
C222
100N
D24
1N4002
1000UF/35V
D25
1N4002
D26
1N4002
+5V
R89
10K
C216
1000U/35V
C231
+VCC
FX-CLIP
-VCC
+5V +5V
U31D
8 9
74HC14
U31F
12 13
74HC14
U32
LM317T
3
Vin
C217
100N C218
C226
10U/25V
C220
100N
2
VIN
U34
LM337T
10 11
J15
1
2
3
4
5
6
7
8
9
10
CON10
U31E
74HC14
+5V
1
1
R90
10K
ADJ
C227
10U/25V
ADJ
R246
+Vout
VOUT
J16
10
CON10
220R
C233
1uF/35V
FOOTSW
2
R238
100R
R240
1.1K
R241
1.1K
R239
100R
3
1
2
3
4
5
6
7
8
9
SW2A
SW 6PIN
+VCC
1
2
SW2B
SW 6PIN
4
5
C228
1000U/25V
C229
1000U/25V
D18
RED
R169
4K7
C232
1U/50V
-VCC+5V
P
3
P
6
+5V
-VCC
R185
680R
100N
C221
100N
R186
680R
1
R187
680R
U33
LM7805CT
Vin
R188
680R
SW1
1
2
3
4
4BIT ENCODER
+5V
GND
2
D27
LED
POWER
R243
2k
4580M
8 4
U27C
3
C230
470U/16V
5
6
-VCC5
+VCC5
C184
0.1u
C185
0.1u
4580M
8 4
U28C
C219
100N
-VCC
+VCC
C186
0.1u
C187
0.1u
+5V+VCC
D
C
B
A
MUTE
C225
C224
100N
1 2 3 4 5 6 7 8
100N
- 9 -
5. Wiring Diagram
D
4
CN501
C
B
A
J15
DSP-313123/2
CN1 CN2
J13:PIN3
J13
J12
J9
J8
J10
J11
POWER-CONNECT
26PIN
CN500
321
CN1
CN11
26PIN
POWERMODII
J16
OEX-400_MIXER
J6
J7
PIN1
PIN2
CN1
D
CN2
PIN1-PIN2 OPEN:AC INPUT=230V
C
PIN1-PIN2 SHORT:AC INPUT=120V
J14
1 2 34
B
A
- 10 -
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