
B–64115EN/01
8. TROUBLESHOOTING
485
A fault occurred on the FSSB (serial servo bus) that connects servo
amplifiers to the CNC.
This alarm is issued if a fault occurs in any of the axis control cards
making up the FSSB, optical cables, and servo amplifiers.
Use the LEDs on the servo amplifiers.
Using the 7–segment LEDs installed on the servo amplifiers, the
defective location can be identified.
Amplifier
0
B
CNC
Amplifier
1
Amplifier
2
Amplifier
3
Amplifier
4
Amplifier
5
A
If portion A, indicated by dotted line, contains the defective location, the
LEDs on the servo amplifiers will be as shown in the table below.
Amplifier
No.
Amplifier
0
Amplifier
1
Amplifier
2
Amplifier
3
Amplifier
4
Amplifier
5
LED
display
“–” “–”
“L”
or
“–”
“U” “U” “U”
In this case, any of the following locations may be defective:
(1)Optical cable connecting together the servo amplifier whose LED is
“L” or “–” and that whose LED is “U”. In the above figure, the optical
cable in portion A may be defective.
(2) Either of the servo amplifier whose LED is “L” or “–” and that whose
LED is “U”. In the above figure, either amplifier 2 or 3 may be defective.
If portion B, indicated by dotted line, contains the defective location, the
LEDs on the servo amplifiers will be as follows:
Amplifier
No.
Amplifier
0
Amplifier
1
Amplifier
2
Amplifier
3
Amplifier
4
Amplifier
5
LED
display
“–” or “U”
In this case, any of the following locations may be defective:
(1)Optical cable connected to the CNC. In the above figure, the optical
cable in portion B may be defective.
(2)Any of the axis control cards in the CNC
(3)First servo amplifier connected. In the above figure, amplifier 0 may
be defective.
8.28
ALARM 926
(FSSB ALARM)
Causes and actions
D Identifying the defective
location
FSSB connection
example