Yamaha Mx12.6 Service Manual

							31 MX12/6
MX20/6
2-5. Separation
With the fader set to the nominal position and the ST (assign switch) turned on at each INPUT channel, turn the Pan control
(BAL control in the case of ST CH INPUT) counterclockwise fully and set the output level of ST L OUT to +20 dBs. Then check
that the level of the leakage to ST R OUT is -50 dBs or less. Also, turn the PAN control clockwise fully and set the output level
of ST R OUT to +20 dBs. Then check that the level of the leakage to ST L OUT is -50 dBs or less.
2-6. LED (PEAK) light-up level
Check that the input level at which each LED lights up w hen a signal is applied to the input of CH INPUT (MICS) or ST INPUT
(either Phone or PIN) is within the range as specified below.
2-7. METER LED light-up level
Check that each METER LED starts to light up when the output level of ST L OUT and ST R OUT is as specified in the table
below. When the level is increased, however, LEDÕs should light up one after another from the bottom.
Check that the Ò0Ó LED starts to light up when the GROUP OUT 1 and 2 level is +5 ± 2 dBs with METER switch set to GROUP SW
ON and GROUP 1-2/3-4 SW OFF and when GROUP OUT 3 and 4 level is +5 ± 2 dBs with METER switch set to GROUP SW ON
and GROUP 1-2/3-4 SW ON. Also, check that the TAPE IN (L, R) level is -7.8 ± 2 dBs when the METER switch is set to TAPE IN.
2-8. Distortion factor
Set each of the INPUT and MASTER controls and the fader to the nominal position and set GAIN as specified from the table1
to the table5. Then check that the distortion factor when a +14dBs output is obtained at each output terminal is 0.1% or less. At
this time C-R/PHONES is excluded. In the case of C-R/PHONES (L, R), set the level control knob at the 12 oÕclock position
which is the nominal position and check that the distortion factor when a 3dBs output is obtained is 0.1% or less.
2-9. Maximum output (1KHz)
Set each of INPUT and MASTERS controls and the fader to the nominal position and GAIN as specified from the table1 to the
table5. Then check that the output obtained at ST OUT L and ST OUT R is +24 dBs and that obtained at GROUP 1 to 4 OUT,
AUX1 OUT, AUX2 OUT and EFFECT OUT is +20 dBs with 1% or less distortion factor. Also, check that the output obtained at
C-R/PHONES (L, R) is +7.5 dBs with 1% or less distortion factor.
2-10. Input converted noise
Make settings as described under Item 1-2 and short-circuit the MIC input terminal of CH INPUT with 150W. Then check that the
noise level obtained at ST L OUT is -43 dBs or less.
If it is not, calculate the input converted noise level (= noise level - channel gain). It should be -127 dBs or less.Note) Use the
DIN AUDIO filter.
Unit [dBs]
Input terminal PEAK LED
CH INPUT -43 ± 2
ST INPUT -17 +2/-3
Unit [dBs]
LED name Meter Switch Light-up start level
PEAK +17 ± 2
+5 +9 ± 2
+3 +7 ± 2
+1 +5 ± 2
0+4 ± 2
-1 ST +3 ± 2
-3 +1 ± 2
-5 -1 ± 2
-7 -3 ± 2
-10 -6 ± 2
-15 -11 ± 4
-20 -16 ± 6 
						

							MX12/6
MX20/6
32
¥ The level of [10] HALL 2 varies but it means nothing problematic.
¥ Apply no input signal, set the CH EFFECT level control to the MIN position and PROGRAM select switch to [11] HALL 3. Then
check that the noise level at ST L OUT and ST R OUT is -54 dBs or less.
¥ Take measurement using the DIN AUDIO filter and with RESPONSE set to AVE.
*1 Execute this check for each of 16 programs from [1] to [16]. Also, input the music source (such as vocal that enables to
recognize the effect easily) and check the effect of the DIGITAL EFFECT function by listening.
2-11. Residual noise
Make settings as described under Item 1-2, set the fader and level control of all input sections to the minimum position and turn
off the assign switch. Then with the fader and volume controls in the master section to the maximum and minimum positions,
check that the noise level obtained then is as specified in the table below.
Use the DIN AUDIO filter.
When measuring C-R/PHONES, set the METER switch to ST and the ST fader to the MIN position.
2-12. Phase
Check that the phase of the signal applied to each input terminal and that of the signal obtained at each output terminal are the
same.
¥ Polarity of connector
[Cannon connector]
pin1 GND   +(HOT)    -(COLD)
pin2 +(HOT)
pin3 -(COLD)
[Phone connector]
Sleeve GND   +(HOT)    -(COLD)
Tip +(HOT)
Ring -(COLD)
2-13. Phantom power (+48V)
Connect a 10kW (1W or more) load resistance between pins [1] and [2] of CH INPUT input connector (MIC) and short-circuit
between pins [2] and [3]. Turn on the phantom switch and check that a +35 ± 3 V voltage is obtained at both ends of the load
resistance then.
2-14. LAMP
Check that the voltage at the LAMP terminal is 12 ± 1 V (AC).(30 ohms load)
2-15. DIGITAL EFFECT
With GAIN control set to the MIN position, input a -40 dBs signal to CH INPUT (MIC) 1. Set each fader and control to the MAX
position and check the output level as specified below is obtained when the DIGITAL EFFECT ON switch is turned on.
Unit [dBs]
Fader/Volume STEREO L, R MONO GROUP1~4 AUX1, 2 EFFECT C-R/PHONES
OUT OUT OUT OUT OUT OUT
MAX -76.5 -78.5 -78.0 -75.0 -74.0 -86.0
MIN -94.0 -94.0 -94.0 -94.0 -94.0 -101.0
Unit [dBs]
Output terminalPROGRAM select switch PARAMETER control Output level
ST L OUTq VOCAL ECHO 1 MIN +3.5 ± 3
ST R OUT
AUX1 OUT +4.0 ± 3
AUX2 OUT
ST L OUTq VOCAL ECHO 1 *1 MAX -5.0 ± 20
ST R OUT!6 GATE REVERB 
						

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MX20/6
34 
						

							35 MX12/6
MX20/6 
						

							MX12/6
MX20/6
36 
						

							37 MX12/6
MX20/6 
						

							MX12/6
MX20/6
38
CIRCUIT DIAGRAMS
Note : See parts list for details of circuit board component parts.
: Metal Film Resister
: Flame Proof Carbon Resistor
: Mylar Capacitor
: Ceramic Capacitor
CIRCUIT DIAGRAM 1/10 (MIAN 1/4) ..................... C1
CIRCUIT DIAGRAM 2/10 (MIAN 1/4) ..................... C2
CIRCUIT DIAGRAM 3/10 (MIAN 1/4) ..................... C3
CIRCUIT DIAGRAM 4/10 (MIAN 1/4) ..................... C4
CIRCUIT DIAGRAM 5/10 (MIAN 4/4) ..................... C5
CIRCUIT DIAGRAM 6/10 (MIAN 1/4, MAIN 2/4,
MAIN 3/4, DCJK 2/2) .............................................. C6
CIRCUIT DIAGRAM 7/10 (DCJK 1/2) ..................... C7
CIRCUIT DIAGRAM 8/10 (IN8 1/2) MX20/6 only ... C8
CIRCUIT DIAGRAM 9/10 (IN8 1/2) MX20/6 only ... C9
CIRCUIT DIAGRAM 10/10 (IN8 1/2, IN8 2/2)
MX20/6 only .......................................................... C10
 CONTENTS
NJM7815FA (XD853A00)
REGULATOR 
NJM7805FA (XJ607A00)
REGULATOR +5V
1: INPUT
2: GND
3: OUTPUT1
2
3
NJM7915FA (XD854A00)
REGULATOR
3
2
1
1: OUTPUT
2: COMMON
3: INPUT1
2
3
NJM7812FA (XJ608A00)
REGULATOR +12V
1: INPUT
2: GND
3: OUTPUT 
						

							   
 
6 5 4
3
H FG E D C B A AH G F E D C B
1
2C1MX12/6 MX20/6MX12/6 MX20/6 MX12/6 MX20/6
CIRCUIT DIAGRAM 1/10(
MAIN1/4)
Not used
Not used UsedUsed R121,
221,
321,
421
C116,
216,
316,
416MX20/6 only
238CC1-8817676
to P.C2-G1
OP AMP
OP AMP
OP AMP
OP AMP
to MAIN 2/4-CN303
MX12/6 only
OP AMP OP AMP
OP AMP OP AMP OP AMP
1
2 1
21
2
(
P.C2-B1)
OP AMP
1
2
OP AMP
1
2
OP AMP OP AMP
1/4to P.C3-G5
to P.C8-G2
(
to IN8 1/2-CN404)
MAIN 
						

							   
 
6 5 4
3 1
2C2
H ABG F CDE AH G BCF E D
MX12/6 MX20/6
MX12/6 MX20/6 MX12/6 MX20/6
CIRCUIT DIAGRAM 2/10(
MAIN1/4)
238CC1-8817676
to P.C3-G1
OP AMP
(
P.C1-B1)from P.C1-G5
OP AMP OP AMPOP AMP OP AMP
OP AMPOP AMP
OP AMP
OP AMP OP AMP
OP AMP
OP AMP
OP AMP
1/4 MAIN