Yamaha Mg12.4 Service Manual

							SERVICE MANUAL

 CONTENTS
SPECIFICATIONS .........................................................3/5
DIMENSIONS .....................................................................7
PANEL LAYOUT .................................................8
MG12/4 CIRCUIT BOARD LAYOUT & WIRING
...............................12
MG16/4 CIRCUIT BOARD LAYOUT & WIRING
...............................14
MG12/4 DISASSEMBLY PROCEDURE ........16
MG16/4 DISASSEMBLY PROCEDURE ........21
IC BLOCK DIAGRAM ............................................26
CIRCUIT BOARDS .................................................27
INSPECTIONS ................................................................39/44
MG12/4 PARTS LIST
MG16/4 PARTS LIST
BLOCK DIAGRAM & LEVEL DIAGRAM
OVERALL CIRCUIT DIAGRAM
MG16/4
,
MIXING CONSOLE
MG12/4
Copyright (c) Yamaha Corporation. All rights reserved.  PDF-K1411      ’05.06
PA011779
MG12/4: 200304-24800
MG16/4: 200304-34800
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							2 MG12/4
MG16/4
IMPORTANT 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
understood 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
personal 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,
certification, recognition of any applicable technical capabilities, or establish a principal-agent
relationship of any form.
The data provided is believed 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 distributor’s 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 Z and must be replaced with parts having specification equal to
those originally installed.
IMPORTANT NOTICE FOR THE UNITED KINGDOM
Connecting the Plug and Cord
IMPORTANT .
The wires in this mains lead are coloured in accordance with the following code:
BLUE:NEUTRAL
BROWN: LIVE
As the colours of the wires in the mains lead of this apparatus may not correspond with the coloured markings identifying
the terminals in your plug proceed as follows:
The wire which is coloured BLUE must be connected to the terminal which is marked with the letter N or coloured BLACK.
The wire which is coloured BROWN must be connected to the terminal which is marked with the letter L or coloured RED.
Making sure that neither core is connected to the earth terminal of the three pin plug.
Z 
						

							3 MG12/4
MG16/4

 SPECIFICATIONS
General Specifications
Where 0 dBu = 0.775 V and 0 dBV = 1 V
1Measured with 12.7 kHz, –6 dB/oct. low pass filter (equivalent to 20 kHz, – ∞filter).
(CH MIC INPUT to ST, GROUP OUT/AUX, EFFECT SEND)
2Turning PAN/BAL to left or right.3Shelving turnover/rolloff frequency: 3 dB before maximum cut or boost. Frequency Characteristics (ST OUT) 20 Hz–20 kHz +1 dB, –3 dB @+4 dBu, 600 
Ω(with gain control at minimum level)
Total Harmonic Distortion (ST OUT) 0.1 % (THD+N) @+14 dBu, 20 Hz–20 kHz, 600 
Ω (MG12/4: CHs 1 to 4, MG16/4: CHs 1 to 8)
(MG12/4: CHs 1 to 4, MG16/4: CHs 1 to 8)  (with gain control at maximum level)
Hum and Noise
1
–128 dBuEquivalent input noise 150 Ω(MG12/4: CHs 1 to 4, 
MG16/4: CHs 1 to 8)
–100 dBu Residual output noise (ST OUT)
–88 dBu (92 dB S/N)ST, GROUP Master fader at nominal level and all Ch 
assign SW’s off.
–81 dBu (85 dB S/N)AUX master control at nominal level; all channel mix 
controls at minimum level.
–64 dBu (68 dB S/N)ST, GROUP Master fader and one Ch fader at nominal 
level.
Maximum Voltage Gain
2
60 dB CH MIC INPUT → CH INSERT OUT
84 dB CH MIC INPUT → GROUP OUT/ST OUT (CH to ST)
94 dB CH MIC INPUT → ST OUT (GROUP to ST)
62.2 dB CH MIC INPUT → REC OUT (CH to ST)
76 dB CH MIC INPUT →AUX SEND (PRE)
86 dB CH MIC INPUT → AUX SEND (POST)
58 dB CH LINE INPUT → GROUP OUT/ST OUT (CH to ST)
84 dB ST CH MIC INPUT → GROUP OUT/ST OUT (CH to ST)
58 dB ST CH LINE INPUT → GROUP OUT/ST OUT (ST CH to ST)
47 dB ST CH LINE INPUT → AUX SEND (PRE)
57 dB ST CH LINE INPUT → AUX SEND (POST)
34 dB ST CH INPUT → GROUP OUT/ST OUT (ST CH to ST)
16 dB RETURN → ST OUT
9 dB RETURN → AUX SEND
27.8 dB 2TR INPUT → ST OUT
Monaural/Stereo Input Gain Control 44 dB variable
Monaural/Stereo High Pass Filter 80 Hz 12 dB/octave
Crosstalk (1 kHz)–70 dB between input channels
–70 dB between input/output channels (CH INPUT)
Monaural/Stereo Input Channel Equalization:
Max. Variation
3
±15 dB
HIGH 10 kHz shelving
MID 2.5 kHz peaking
LOW 100 Hz shelving
Monaural/Stereo Input Peak IndicatorOn each channel: red indicator lights if post-EQ signal (on ST channels, if either post-EQ sig-
nal or post-mic-amp signal) comes within 3 dB of the clipping level.
Level MetersTwo 12-point LED meters
Peak point: red indicator
+5, +3, +1, and 0 points: yellow indicators
–1, –3, –5, –7, –10, –15, –20: green indicators
Phantom +48 VDC Power (Balanced input) Supplied when Phantom +48 V switch is ON.
Included Accessory Power adaptor (PA-20)
Power SupplyUSA and Canada: 120 V AC, 60 Hz
Europe: 230 V AC, 50 Hz
Australia: 240 V AC, 50 Hz
Korea: 220 V AC, 60 Hz
China: 220 V AC, 50 Hz
Power Consumption MG16/4: 36 W MG12/4: 29 W
Max. Dimensions (W 
×H ×D) MG16/4: 423 ×108 ×416.6 mm MG12/4: 322 ×108×416.6 mm
Weight  MG16/4: 5.2 kg MG12/4: 5.0 kg 

 
						

							4 MG12/4
MG16/4
Input Specifications
Where 0 dBu = 0.775 V and 0 dBV= 1 V* Input sensitivity: the lowest level that will produce the nominal output level when the unit is set to maximum gain.
Output Specifications
Where 0 dBu = 0.775 V and 0 dBV= 1 V
Input ConnectorGainInput 
ImpedanceAppropriate 
ImpedanceSensitivity*Rated LevelMax. Before 
ClippingConnector 
Specifications
MIC INPUT
(MG16/4: CHs 1 to 8)
(MG12/4: CHs 1 to 4)–60
3 kΩ50–600 Ω mic
–80 dBu 
(0.078 mV)–60 dBu 
(0.775 mV)–40 dBu 
(7.75 mV)
XLR-3-31 type (balanced)
–16–36 dBu 
(12.3 mV)–16 dBu 
(123 mV)+4 dBu 
(1.23 V)
LINE INPUT
(MG16/4: CHs 1 to 8)
(MG12/4: CHs 1 to 4)–34
10 kΩ600 Ω line
–54 dBu 
(1.55 mV)–34 dBu 
(15.5 mV)–14 dBu 
(155 mV)Phone jack (TRS) 
(balanced [T: hot; R: cold; 
S: ground])
+10–10 dBu 
(245 mV)+10 dBu 
(2.45 V)+30 dBu 
(24.5 V)
ST CH MIC INPUT
(MG16/4: CH9(L)/CH10(R),
CH11(L)/CH12(R))
(MG12/4: CH5(L)/CH6(R),
CH7(L)/CH8(R))–60
3 kΩ50–600 Ω mic
–80 dBu
(0.078 mV)–60 dBu 
(0.775 mV)–40 dBu 
(7.75 mV)
XLR-3-31 type (balanced)
–16–36 dBu 
(12.3 mV)–16 dBu 
(123 mV)–10 dBu 
(245 mV)
ST CH LINE INPUT
(MG16/4: CH9(L)/CH10(R),
CH11(L)/CH12(R))
(MG12/4: CH5(L)/CH6(R),
CH7(L)/CH8(R))–34
10 kΩ600 Ω line
–54 dBu 
(1.55 mV)–34 dBu 
(15.5 mV)–14 dBu 
(155 mV)
Phone jack (unbalanced)
+10–10 dBu
(245 mV)+10 dBu
(2.45 V)+30 dBu 
(24.5 V)
ST CH INPUT
(MG16/4: CH13(L)/CH14(R),
CH15(L)/CH16(R))
(MG12/4: CH9(L)/CH10(R),
CH11(L)/CH12(R))
10 kΩ600 Ω line–30 dBu 
(24.5 mV)–10 dBu 
(245 mV)+10 dBu 
(2.45 V)Phone jack (unbalanced);
RCA pin jack
CH INSERT IN 
(MG16/4: CHs 1 to 8)
(MG12/4: CHs 1 to 4)10 kΩ600 Ω line–20 dBu 
(77.5 mV)0 dBu 
(0.775 V)+20 dBu 
(7.75 V)Phone jack (TRS) 
(unbalanced [T: out; R: in; 
S: ground])
RETURN (L, R)10 kΩ600 Ω line–12 dBu 
(195 mV)+4 dBu 
(1.23 V)+24 dBu 
(12.3 V)Phone jack (TRS) (unbalanced 
[T: hot; S: ground])
2TR IN (L, R)10 kΩ600 Ω line–26 dBV 
(50.1 mV)–10 dBV 
(316 mV)+10 dBV 
(3.16 V)RCA pin jack
Output ConnectorsOutput 
ImpedanceAppropriate 
ImpedanceRated LevelMax. Before 
ClippingConnector Specifications 
ST OUT (L, R)150 Ω600 Ω line+4 dBu (1.23 V)+24 dBu (12.3 V)XLR-3-32 type (balanced)
Phone jack (TRS)
(balanced [T: hot; R: cold; S: ground])
GROUP OUT (1-2)
AUX SEND (1-2)150 Ω10 kΩ line+4 dBu (1.23 V)+20 dBu (7.75 V)Phone jack (TRS)
(impedance balanced [T: hot; R: cold; S: 
ground])
CH INSERT OUT
(MG16/4: CHs 1 to 8)
(MG12/4: CHs 1 to 4)150 Ω10 kΩ line0 dBu (0.775 V)+20 dBu (7.75 V)Phone jack (TRS) 
(unbalanced [T: out; R: in; S: ground])
REC OUT (L, R)600 Ω10 kΩ line–10 dBV (316 mV)+10 dBV (3.16 V)RCA pin jack
C-R OUT (L, R)150 Ω10 kΩ line+4 dBu (1.23 V)+20 dBu (7.75 V)Phone jack (TRS) 
(impedance balanced [T: hot; R: cold; S: 
ground])
PHONES 100 Ω40 Ω phone3 mW75 mWStereo phone jack



 
						

							5 MG12/4
MG16/4
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							6 MG12/4
MG16/4
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7.75 mV£ 
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–16–36 dBu
¢ 12.3 mV
£ –16 dBu
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£ +4 dBu
¢  1.23 V
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LINE INPUT
(MG16/4
 CH1
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(MG12/4
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 600 

å ï –54 dBu
¢ 1.55 mV
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ST CH MIC INPUT
(MG16/4CH9(L)/CH10(R)z
CH11(L)/CH12(R))
(MG12/4CH5(L)/CH6(R)z
CH7(L)/CH8(R))
–603 k

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ST CH LINE INPUT
(MG16/4
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z 
CH11(L)/CH12(R))
(MG12/4 
CH5(L)/CH6(R)z 
CH7(L)/CH8(R))–3410 k

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å ï –54 dBu
¢ 1.55 mV
£ –34 dBu
¢  15.5 mV
£ –14 dBu
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£
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+10–10 dBu
¢ 245 mV£ +10 dBu
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ST CH INPUT
(MG16/4 
CH13(L)/CH14(R)z 
CH15(L)/CH16(R))
(MG12/4 
CH9(L)/CH10(R)z 
CH11(L)/CH12(R))10 k
 
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å ï –30 dBu
¢ 
24.5 mV£ –10 dBu
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245 mV£ +10 dBu
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2.45 V£
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RCA
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CH INSERT IN 
(MG16/4 
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(MG12/4 
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å ï –20 dBu
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77.5 mV£ 0 dBu
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0.775 V£ +20 dBu
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RETURN (LzR) 10 k
 
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195 mV£ +4 dBu
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1.23 V£ +24 dBu
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2TR IN (L
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¢ 50.1 mV
£ –10 dBV
¢  316 mV
£ +10 dBV
¢  3.16 V
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£ +20 dBu
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10 k
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10 k
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PHONES
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40 

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							7 MG12/4
MG16/4

 DIMENSIONS

 MG16/4 
 MG12/4
393
31.5
309.6 D 416.6
H 108
101.3 3
W 423
428
27.5
480
When mounted on rack
317.4
D 416.6
325.6
102.62 H 108W 322
480 322
When mounted on rack
Units : mm
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							8 MG12/4
MG16/4
q[GAIN] Control
w[PEAK] Indicator
e[ 
80 ] Switch (High Pass Filter)
rEqualizer ([HIGH], [MID], [LOW])
t[AUX1] and [AUX2] Controls
y[PRE] Switch
u[PAN] Control (MG16/4: CHs 1 to 8. MG12/
4: CHs 1 to 4)
[PAN/BAL] Control (MG16/4: CHs 9/10 and
11/12. MG12/4: CHs 5/6 and 7/8)
[BAL] Control (MG16/4: CHs 13/14 and 15/
16. MG12/4: CHs 9/10 and 11/12)
i[ 
 ] ST Switch
o[PFL] (Pre-Fader Listen) Switch
!0[GROUP] Switch
!1Channel Fader

 PANEL LAYOUT
Note: Within this manual, all panel illustrations show the MG16/4 panel.
						

							9 MG12/4
MG16/4
q[ST] Master Fader
w[GROUP 1-2] Fader
e[ TO ST ] Switch
rMaster SEND ([AUX1] and [AUX2] Controls)
tRETURN ([AUX1], [AUX2], and [ST] Controls)
y[2TR IN] Control
u[PHANTOM +48V] Switch
iLevel-Meter Signal Switches
(ST-GROUP Toggle Switch and 2TR IN Switch)
o[C-R/PHONES] Control
!0Level Meter
!1[POWER] Indicator
!2[PHONES] jack
y
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!1
!0
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							10 MG12/4
MG16/4
qChannel Input jacks
[MIC] jacks (MG16/4: CHs 1 to 8, 9/10, 11/12.
MG12/4: CHs 1 to 4, 5/6, 7/8)
[LINE] jacks (MG16/4: CHs 1 to 8. MG12/4: CHs
1 to 4)
w[INSERT I/O] Jacks
(MG16/4: CHs 1 to 8. MG12/4: CHs 1 to 4)
eChannel Input jacks
Phone type (MG16/4: CHs 9/10 to 15/16. MG12/4:
CHs 5/6 to 11/12)
RCA pin type (MG16/4: CHs 13/14, 15/16. MG12/
4: CHs 9/10, 11/12)
r[GROUP OUT] (1, 2) Jacks
t[ST OUT] (L, R) Jacks
y[C-R OUT] Jacks
u[SEND] Jacks
i[RETURN L] (MONO), [RETURN R] Jacks
o[REC OUT] (L, R) Jacks
!0[2TR IN] Jacks
!1[POWER] Switch
!2[AC ADAPTOR IN] Connector
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o!0
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!1
!2tr qw

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