Yamaha SB168-ES Service Manual page 75

2-4. INPUT 1 – 16 GAIN MIN & MAX
Measure the CH 1 to 8 and then measure the CH 9 to 16.
Inspection patch should be changed to inspect CH 9 to 16ch.
AVS-ESMonitor runs automatically to change the patch as
necessary.
A. GAIN +10 dBu
Select the test program menu "GAIN MIN" for CH 1 to 8. (See
page 55)
Select the test program menu "AD9-16ch GAIN MIN" for CH
9 to 16. (See page 55)
① Gain
(INPUT 1 to 8 are already measured and can be omitted.)
Input Frequency Input Level
1 kHz +10 dBu
② Distortion
(INPUT 1 to 8 are already measured and can be omitted.)
Input Frequency Output Level
1 kHz +4 dBu
③ Residual noise
Short the INPUT to be measured with 150Ω.
(INPUT 1 to 8 are already measured and can be omitted.)
Permissible Range
-80 dBu or less
④ Level Difference between channels
The range of difference in the gain measured in the item ①
should be as follows.
Permissible Range
Within 1.5 dB
B. GAIN -62 dBu
Select the test program menu "GAIN MAX" for CH 1 to 8.
(See page 55)
Select the test program menu "AD9-16ch GAIN MAX" for
CH 9 to 16. (See page 55)
① Gain (INPUT 1 – 16)
Input Frequency Input Level
1 kHz -62 dBu
② Distortion (INPUT 1 – 16)
Input Frequency Output Level
1 kHz +4 dBu
Specifi ed Output Level Permissible Range
+4 dBu +4 ±2 dBu
Permissible Range
0.05% or less
Specifi ed Output Level Permissible Range
+4 dBu +4 ±2 dBu
Permissible Range
0.1% or less
③ Noise level EIN (INPUT 1 – 16)
Parameters
Short the INPUT to be measured with 150Ω.
Permissible Range
-62 dBu or less
If the measured value is out of the above permissible range,
check the level as follows.
Measured value - (gain at 1kHz) ≦ -128
④ Level Difference between channels (INPUT 1 – 16)
The range of difference in the gain measured in the item ①
should be as follows.
Permissible Range
Within 2.5 dB
C. Phantom power (INPUT 1 and 9)
Select the test program menu "+48V ON". (See page 55)
Select the test program menu "+48V OFF" to conduct
Discharge Test when the switch is turned off. (See page 55)
The voltage should be as follows when the +48V MASTER
switch is turned on with the No. 2 and No. 3 pins of XLR
shorted and 10 kΩ load connected between the No. 2 and No. 1
pins.
Permissible Range
DC 33.6 to 36.1 V
Check also that discharging starts quickly when the +48V
MASTER switch is turned OFF.
Take measurement of OUTPUT 1 and 9 as samples.
2-5. Fan check
Check that the rotating speed of the fan increases when the
FAN HIGH, LOW switch on the rear panel is set to HIGH side
and that the rotating speed of the fan decreases when set to
LOW side.
SB168-ES
75