Yamaha RX-777 Service Manual page 8

RX-777
1. Test mode for the DISPLAY to light all segments.
Turn the POWER SW ON while pressing the EDIT and
No. 8 keys simultaneously. The unit enters the TEST
mode for the DISPLAY to light all segments.
2. Test mode for the microprocessor
software version check.
While in the DISPLAY test mode, push the No. 1 key to enter
the TEST mode for the microprocessor software version
check.
3. Memory reset mode
While in the DISPLAY test mode, push the A/B/C/D/E
key to enter the Memory reset mode and all RAM
settings are reset to the factory settings.
4. Test mode to display the Protection
PS port (pin No. 80) input voltage.
Turn the POWER SW ON while pressing the EDIT and
No. 6 keys simultaneously. The unit enters the TEST
mode to display the Protection PS port input voltage as
an AD value for 3 sec.
The microprocessor will not respond to any commands
while in this mode.
5. Test mode to display the Protection
DC port (pin No. 79) input voltage.
Turn the POWER SW ON while pressing the EDIT and
No. 7 keys simultaneously. The unit enters the TEST
mode to display the Protection DC port input voltage as
an AD value for 3 sec.
The microprocessor will not respond to any commands
while in this mode.
Cancel:
When the POWER is turned OFF, the TEST mode is cancelled.
PROTECTION FUNCTION
When the microprocessor detect an abnormal condition, the Power is turned off.
Vref is the AD reference Voltage. The microprocessor compares the monitored voltage relative to Vref = 255.
PS Error Detection
PS error detection begins 1 sec. after Power ON. If the monitored level is lower than 53/255 Vref or higher than
134/255 Vref (AD value), protection is activated.
Output DC Voltage Detection
DC voltage detection begins 4.4 sec. agter Power ON. If the monitored level is lower than 12/255 Vref or higher than
115/255 Vref (AD value), protection is activated.
Over Current Detection
Over current detection begins immediately after Power ON. If the monitored level is High, protection is activated.
7
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Abnormal
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Normal
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Abnormal
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Abnormal
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Normal
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Abnormal