Fanuc Alarm AL-U FSSB Alarm Information by KFASLLC

KFAS: Fanuc CNC Parts, Service, & Repair

Fanuc ALARM AL-U aiSV-B

Alarm AL-U Fanuc 0iF or 31iB on aiSV-B means,
SV FSSB communication error (COP10B)
Cause and troubleshooting
(a) Replace the optical cable (COP10B) of the servo amplifier that is the closest to the CNC of those displaying U. (the cable between UNIT2 and UNIT3.)
(b) Replace the servo amplifier that is the closest to the CNC of those displaying U. In the following example, replace UNIT 3.)
(c) Replace the servo amplifier on the COP10B side that is the closest to the CNC of those displaying U.
(UNIT2.)

(d) Replace the CNC servo card.

A06B6240 aiSV-B B65515EN Maintenance Manual

*CAUTION: High Voltage present.
Note: Some Machine's electrical cabinet doors are equipped with "door interlock" that will cause the breaker to trip when the door is open.
See the machine's manual for information on how to bypass so that you can observe the alarm LED status

Fanuc CNC Alarm App for your smart phone