Yamaha Mx12.6 Service Manual

							MX12/6
MX20/6
1
SERVICE MANUAL
PA011541
MX12/6  20001210-69800
MX20/6  20001210-99800  1.419K-7721 K          Printed in Japan 2000.12
HAMAMATSU, JAPAN
 CONTENTS
This document is printed on chlorine free (ECF) paper with soy ink.
SPECIFICATIONS ................................................ 3/5
DIMENSIONS ............................................................ 6
PANEL LAYOUT .................................... 7
BLOCK & LEVEL DIAGRAM .......................................................10
WIRING ................................................................... 12
CIRCUIT BOARD LAYOUT ............... 14
DISASSEMBLY PROCEDURE ............................ 15
LSI PIN DESCRIPTION .............................. 18
IC BLOCK DIAGRAM ................................. 20
CIRCUIT BOARDS ....................................... 21
INSPECTIONS ........................................................... 33
CIRCUIT DIAGRAMS ............................................. 38
PARTS LIST
MIXING CONSOLE
MX20/6 MX12/6 
						

							MX12/6
MX20/6
2 2
IMPOR TANT NOTICE
This manual has been provided for the use of authorized Yamaha Retailers and their service personnel. It has been assumed
that basic service procedures inherent to the industry, and more specifically Yamaha Products, are already known and under-
stood by the users, and have therefore not been restated.
WARNING :Failure to follow appropriate service and safety procedures when servicing this product may result in per-
sonal injury, destruction of expensive components and failure of the product to perform as specified. For
these reasons, we advise all Yamaha product owners that all service required should be performed by an
authorized Yamaha Retailer or the appointed service representative.
IMPORTANT :This presentation or sale of this manual to any individual or firm does not constitute authorization certifi-
cation, recognition of any applicable technical capabilities, or establish a principal-agent relationship of
any form.
The data provided is belived to be accurate and applicable to the unit(s) indicated on the cover. The research engineering, and
service departments of Yamaha are continually striving to improve Yamaha products. Modifications are, therefore, inevitable
and changes in specification are subject to change without notice or obligation to retrofit. Should any discrepancy appear to
exist, please contact the distributorÕs Service Division.
WARNING :Static discharges can destroy expensive components. Discharge any static electricity your body may have
accumulated by grounding yourself to the ground bus in the unit  (heavy gauge black wires connect to
this bus.)
IMPORTANT :Turn the unit  OFF  during disassembly and parts replacement. Recheck  all  work before you apply power
to the unit.
WARNING: CHEMICAL CONTENT NOTICE!
The solder used in the production of this product contains LEAD. In addition, other electrical/electronic and/or plastic (Where
applicable) components may also contain traces of chemicals found by the California Health and Welfare Agency (and possibly
other entities) to cause cancer and/or birth defects or other reproductive harm.
DO NOT PLACE SOLDER, ELECTRICAL/ELECTRONIC OR PLASTIC COMPONENTS IN YOUR MOUTH FOR ANY REASON WHAT
SO EVER!
Avoid prolonged, unprotected contact between solder and your skin! When soldering, do not inhale solder fumes or expose
eyes to solder/flux vapor!
If you come in contact with solder or components located inside the enclosure of this product, wash your hands before handling
food.
WARNING
Components having special characteristics are marked             and must be replaced with parts having specification equal to those
originally installed.
2 
						

							MX12/6
MX20/6
3
SPECIFICATIONS
Frequency response20Hz—20kHz +1dB, -3dB     @+4dB, 600ohms (Input Gain control at minimum level)
Total harmonic distortion
						

							MX12/6
MX20/6
4
 Input Specifications
Input Gain Input NominalInput level
Connector typeconnectors Control impedance impedance
Sensitivity *1 Nominal Max. before clipping
MIC INPUT-60
5k ohms50-600ohms
 mics-80 dB (0.078mV) -60 dB (0.775mV) -40 dB (7.75mV)
XLR-3-31 type *2(1-n *5)
-16 -36 dB (12.3mV) -16 dB (123mV) +4 dB (1.23V)
LINE INPUT-34
50k ohms 600ohms lines-54 dB (1.55mV) -34 dB (15.5mV) -14 dB (155mV)
Phone jack (TRS) *2(1-n *5)
+10 -10 dB (245mV) +10 dB (2.45V) +30 dB (24.5V)
ST INPUT-34
10k ohms 600ohms lines-54 dB (1.55mV) -34 dB (15.5mV) -14 dB (155mV)
RCA phono jack(*7)
+10 -10 dB (245mV) +10 dB (2.45V) +30 dB (24.5V)Phone jack *3
RETURN (L, R) 10k ohms 600ohms lines -12 dB (195mV) +4 dB (1.23V) +20 dB (7.75V) Phone jack *3
TAPE IN (L, R) 10k ohms 600ohms lines -26 dBV (50.1mV) -10 dBV (316mV) +10 dBV (3.16V) RCA phono jack
CH INSERT IN
10k ohms 600ohms lines -20 dB (77.5mV) 0 dB (0.775V) +20 dB (7.75V) Phone jack (I/O) *4
(1-n *6)
*1 Input sensitivity: the lowest level that will produce the nominal
output level when the unit is set to maximum gain.
*2 XLR type connector, phone jack (TRS) (T=Hot, R=Cold, S=Gnd):
balanced type.
*3 Phone jack: unbalanced type.*4 Phone jack (I/O) (T=Out, R=In, S=Gnd): unbalanced type.
*5 n=8 (MX12/6), n=16 (MX20/6)
*6 n=4 (MX12/6), n=8 (MX20/6)
*7 9/10, 11/12 (MX12/6), 17/18, 19/20 (MX20/6)
  • 0dB=0.775Vrms, 0dBV=1Vrms
 Output Specifications
Output connectorsOutput NominalOutput level
Connector typeimpedance impedance
Nominal Max. before clipping
ST OUT (L, R) , MONO OUT 150ohms 600ohms lines +4 dB (1.23V) +24 dB (12.3V) XLR-3-32 type *1
GROUP OUT (1-4)
AUX SEND (1, 2) 75ohms 600ohms lines +4 dB (1.23V) +20 dB (7.75V) Phone jack (TRS) *2
EFFECT SEND
C-R/PHONES (L, R) 100ohms10k ohms lines +4 dB (1.23V) +20 dB (7.75V)
ST phone jack (TRS) *340ohms phones 3mW 75mW
REC OUT (L, R) 600ohms 10k ohms lines -10 dBV (316mV) +10 dBV (3.16V) RCA phono jack
CH INSERT OUT (1-n *5) 600ohms 10k ohms lines 0 dB (0.775V) +20 dB (7.75V) Phone jack (TRS) *4
*1 XLR type connector: balanced type.
*2 Phone jack (TRS)  (T=Hot, R=Cold, S=Gnd): impedance balanced
type.
*3 ST phone jack (TRS) (T=L, R=R, S=Gnd): unbalanced type.*4 Phone jack (I/O) (T=Out, R=In, S=Gnd): unbalanced type.
*5 n=4 (MX12/6), n=8 (MX20/6)
  • 0dB=0.775Vrms, 0dBV=1Vrms 
						

							MX12/6
MX20/6
5 
						

							MX12/6
MX20/6
6
Units: mm
DIMENSIONS
35
658
58835
11835 35
< MX20/6 >
< MX12/6 >
46854.6
17.6
438
368
268
384
118
46 
						

							MX12/6
MX20/6
7
1
2
3
4
5
6
7
8
9
PANEL LAYOUT
Channels
1-8 (MX12/6)
1-16 (MX20/6)
(Monaural)Channels
9-12 (MX12/6)
17-20 (MX20/6)
(Stereo)
1
2
3
6
7
8
9
8
44
55
GAIN Control
PEAK Indicator
Equalizer
AUX1, AUX2 Controls
POST Switch
EFFECT Control
PAN Control (MX12/6:CH1-8, MX20/6:CH1-16)
BAL Control (MX12/6:CH9-12, MX20/6:CH17-20)
GROUP, ST Select Switches
Channel Fader
 
Channel Control Section 
						

							MX12/6
MX20/6
8
1314
12
1011
8
2
1
43
6
7
5
9
1
2
3
4
5
6
7
8
9
10
11
12
13
14
ST Master Fader
MONO Control
GROUP 1-4 Faders
TO ST Switch
SEND
RETURN
DIGITAL EFFECT
TAPE IN Control
ST GRAPHIC EQUALIZER
C-R/PHONES Output and Meter Select Switch
C-R/PHONES Control
LEVEL Meter
POWER Indicator
LAMP Connector
 
Master Control Section 
						

							MX12/6
MX20/6
9
1245
3
765431
2
8
 
Connector Section
 
Rear Panel
1
2
3
4
5INPUT Jacks (MX12/6:CH1-8, MX20/6:CH1-16)
INPUT Jacks (MX12/6:CH9-12, MX20/6:CH17-20)
ST OUT (L, R) Jacks
MONO OUT Jack
C-R/PHONES Jack
1
2
3
4
5
6
7
8INSERT I/O Jack (MX12/6:CH1-4, MX20/6:CH1-8)
PHANTOM +48V Switch
SEND Jack
RETURN L (MONO), R Jacks
GROUP OUT (1-4) Jacks
TAPE IN (L, R) Jacks
REC OUT (L, R) Jacks
POWER Switch 
						

							MX12/6
MX20/6
10
BLOCK & LEVEL DIAGRAM
+30dB
+20dB
+10dB
0dB
-10dB
-20dB
-30dB
-40dB
-50dB
-60dB
CH INPUT LINE IN
GAIN Min.[+10dB]
CH INPUT MIC IN
GAIN Min.[-16dB]
CH INPUT LINE IN
GAIN Max.[-34dB]
CH INPUT MIC IN
GAIN Max.[-60dB]ST INPUT
GAIN Min.[+10dB] ST INPUT
GAIN Min.[+10dB]
ST INPUT
GAIN Max.[-34dB]Max. Before Clip
INSERT I/O [0dB]Max. Before Clip
TAPE IN [-10dBV]
FaderRETURN [+4dB]
CH & ST INPUT to GROUP/STEREO [0dB]
RETURN to AUX/STEREO [-2dB]
CH & ST INPUT to AUX/EFFECT [-6dB]
TAPE IN & DSP to AUX/STEREO [-6dB]AUX
EFFEC
TControMaster
CH INPUTMX12/6:1~4ch
MX20/6:1~8ch
MIC INPUT[-60~-16dB]
LINE INPUT[-34~+10dB]
INSERT I/O[0dB]
PADPHANTOM
(8ch/sw)from DC Power Supply
HA
GAIN
[-60dB~-16dB]
[-34dB~+10dB][0dB]Lo
Mid
Hi
3-Stage EQ
PEAK
Ch.Fader[-10dB]
BA[0dB][0dB]
1-2
3-4
ST
[-6dB]PAN
POSTAUX1
AUX2
EFFECT
CH INPUT
MX12/6:5~8ch
MX20/6:9~16ch
MIC INPUT[-60~-16dB]
LINE INPUT[-34~+10dB]from DC Power Supply
PHANTOM(8ch/sw)
PADHA
GAIN[-60dB~-16dB]
[-34dB~+10dB][0dB]Lo
Mid
Hi
3-Stage EQ
PEAK
Ch.Fader[-10dB]
BA[0dB][0dB]
1-2
3-4
ST
[-6dB]PAN
POSTAUX1
AUX2
EFFECT
ST INPUT
MX12/6: 9/10ch, 11/12ch
MX20/6:17/18ch, 19/20ch
[-34~+10dB]
L
RHA
HA
[0dB]
GAIN[-34dB~+10dB]
3-Stage EQ
Lo
Mid
Hi
3-Stage EQ
PEAK
BABA
ST Ch.Fader[-10dB][0dB]
SUMBAL
[0dB]
POST
1-2
3-4
ST
[-6dB]
AUX1
AUX2
EFFECT
TAPE IN
[-10dBV]L
RBA
BA[0dB][-6dB]TAPE IN
RETURN
[+4dB]
L/MONO
RBA
BA[+4dB]
[-2dB]
AUX2 ST
AUX1
[0dB]
DIGITAL
EFFECT
ON
[-6dB]
AUX2 ST
AUX1
STEREO R
EFFECTSTEREO L GROUP4 GROUP3GROUP2 GROUP1
AUX1
AUX2 STEREO R
EFFECT STEREO LGROUP4GROUP3GROUP2 GROUP1
AUX1
AUX2
GROUP1 
[0dB]
SUM
SUM SUMSUM[0dB]
[0dB]
[0dB]
[0dB]
[0dB][-10
d
GROUP2 [-10d
GROUP3 [-10d
GROUP4 [-10d
SUM SUM
INVINV
[
SUM
SUM[0dB]
[0dB]
SUM
PROGRAM
PARAMETER
DI
EF
L
[0dB]
A A
1/4
IC101, 201, 301, 401
2
31IC503
6
2
1 7
JK102, 202, 302, 402JK101
JK201
JK301
JK401
MAIN
ICF01
21ICD01
21
ICD01
67
ICE01
21
ICE01
67
ICG01
21ICG01
67ICF01
67
ICI01
21
ICI61
67ICI01
67
1/4 MAIN
1/4 MAIN
1/4
IC501, 601, 701, 801
2
31IC703
6
2
1 7
IC903
ICA03 21
67
21
67
IC904 21
31
57 67 IC901
21
ICA01 21 JK501
JK601
JK701
JK801
JK901
JKA01
JK902
JKA02JK502
JK602
JK702
JK802
MAIN
1/4 MAIN
1/4 MAIN
1/4
MAIN
JK305
CN302-14CN202-1
CN301-7CN201-4
CN204-
CN204-10 CN304-3 CN204-4~8
CN
3
CN3CN204-1~3CN304
CN301-9CN201-2 CN302-13CN202-2ICB51
31
ICB01
57
ICB01 ICB51
2/2 DCJK
2/2 DCJK