Yamaha PSR-S770 Service Manual page 43

LCD■display
023■:■DAC■MUTE■Check
024■:■MUTE■Check
025■:■Emergency■Circuit■
Check
Checks whether the DAC MUTE for the DAC IC's output works properly or not.
1) Press the [START/STOP] button to produce the C5 sine wave sound. "OFF" is shown on the LCD.
2) Press the TAB [>] button to activate the DAC MUTE circuit.
"ON" is shown on the LCD, and all the output from the speakers, PHONES, and OUTPUT jacks are
muted.
3) Press the TAB [<] button to cancel the DAC MUTE circuit.
"OFF" is shown on the LCD and the C5 sound is produced.
4) Press the [START/STOP] button to stop the sound and to exit the TEST item.
Checks whether the MUTE for all outputs works properly or not.
1) Press the [START/STOP] button to produce the C5 sine wave sound. "OFF" is shown on the LCD.
2) Press the TAB [>] button to activate the MUTE circuit.
"ON" is shown on the LCD, and all the output from the speakers, PHONES, and OUTPUT jacks
are muted.
3) Press the TAB [<] button to cancel the MUTE circuit. At this time, check that the muting relay on
the HP circuit board works properly.
"OFF" is shown on the LCD and the C5 sound is produced.
4) Press the TAB [>] button to activate the MUTE circuit.
5) Connect the level meter to the OUTPUT jacks.
6) Measure the output levels and confirm that the measured values are within the specified range.
[OUTPUT] (10kW load)
L/L+R: -35.0 dBu or less
7) Press the [START/STOP] button to stop the sound and to exit the TEST item.
Caution:
When checking the output of the speakers, do not insert any plug to the PHONES jack.
Checks whether the Fail-Safe Circuit for digital volume control works properly or not.
1) Press the [START/STOP] button to produce the A3 sine wave sound. "OFF" is shown on the LCD.
2) Press the TAB [>] button to activate the Fail-Safe Circuit function.
"ON" is shown on the LCD, and all the output from the speakers, PHONES, and OUTPUT jacks
are muted.
3) Press the TAB [<] button to cancel the Fail-Safe Circuit function. At this time, check that the
muting relay on the HP circuit board works properly.
"OFF" is shown on the LCD and the A3 sound is produced.
4) Press the [START/STOP] button to stop the sound and to exit the TEST item.
Caution:
When checking the output of the speakers, do not insert any plug to the PHONES jack.
Test■items■and■judging■conditions
R: -35.0 dBu or less
PSR-S770/PSR-S970
43