Yamaha M7CL-32, Руководство по обслуживанию

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M7CL-32/M7CL-48
118
INSPECTIONS
1. Preparation
1-1. Measuring Instruments
Use measuring instruments which can measure the inspection
items accurately with confidence.
Input impedance of the measuring device should be 100 k
Ω
or more.
· System Two
· Tester
· Filter (12.7 kHz, –6 dB/OCT)
· Level meter
1-2. Parameters
◊
Unless otherwise specified, the parameter settings are as
follows.
· Set the WORD CLOCK to INT 48 kHz.
· Set the “+48V MASTER” to ON.
· Turn on only the channel being measured.
PAN : CENTER
GAIN : MIN
FADER : NOMINAL (0 dB)
PHONES LEVEL : MAX
TALKBACK GAIN : MAX
· 0 dBu = 0.775 Vrms
· 0 dBFS = 0 dB, full scale
· Set the oscillator output impedance to 150
Ω
.
· Correct with LPF at 12.7 kHz, –6 dB/OCT during noise
measuring.
(For measurement, use the average values and not effective
values.)
· Correct with LPF at 80 kHz, –18 dB/OCT during distortion
measuring.
◊
For analog output inspection, add or change parameter settings
as follows.
· For maximum output measurement, unless otherwise
specified, output 0 dB from the internal oscillator.
· Set the analog output loads as follows:
OMNI OUT: 600
Ω
PHONES(x 2): 8
Ω
1-3. Updating the Program
If the main program is not the latest version, it is necessary to
update it to the latest version.
∗
For the latest version, download the latest program from the
YSISS home page and save it in the USB memory device.
(1) How to check the version of the main program
Press the MENU in the LCD screen and the current version will
be shown in the “SETUP” page screen.
(2) How to write programs
For the program writing procedure, refer to the “LOADING THE
PROGRAM” section in the “SERVICE CHECK PROGRAM”.
(See page 126)
1-4. Initialization
Refer to “Initializing the internal memory” for Initializing the
internal memory. (See page 189)
1-5. Fader Calibration
Refer to “Calibration function: Calibrating faders” for calibrating
faders. (See page 192)
1-6. CPUM circuit board SRAM Backup Inspection
Check that “== INITIALIZE MENU ==” does not appear on
the LCD screen when the power is turned on.
2. ANALOG IN/OUT Characteristic Inspection
2-1. OMNI OUT 1—16
Parameters: Input from INPUT (XLR) of CH1.
Assign CH1 to OMNI OUT 1—16.
(1) Gain (OMNI OUT 1—16)
(2) f characteristics (OMNI OUT 1—16)
Parameters: 1 kHz is used as the reference of the permissible range.
(3) Distortion factor (OMNI OUT 1—16)
(4) Residual noise(OMNI OUT 1—16)
Parameters: Turn off STEREO.
(5) OMNI OUT 1—16 level difference
Adjust the range of difference in the gain measured in item (1)
above as follows.
(6) Crosstalk between adjacent channels (OMNI OUT 1—16)
Parameters: Turn on OMNI OUT of only one odd number channel
for output with OMNI OUT of other channels turned
off and measure the noise level of even number
channels next to the odd number channel on both side.
Perform the same check on the even number channels.
Input Frequency Input Level Prescribed Output Level Permissible Range
1 kHz +10 dBu +4 dBu +4
±
2 dBu
Input Frequency Input Level Permissible Range
20 Hz +10 dBu –1.5 — +0.5 dB
20 kHz +10 dBu –1.5 — +0.5 dB
Input Frequency Output Level Permissible Range
1 kHz +22 dBu 0.01 % or below
Permissible Range
–86 dBu or below
Permissible Range
Within 1 dB
Input Frequency Output Level Permissible Range
(Odd Channel) (Even Channel)
1 kHz +23 dBu –57 dBu or below