Fanuc alarm U
αi SVM · Fanuc αi SVM
What it means
Inverter: FSSB fiber communication error on COP10B side - unit failing to receive data from CNC/master direction.
Likely causes
- COP10B optical fiber cable failure (cable nearest the affected unit)
- SVM optical interface failure
- Upstream SVM COP10B-side failure
- CNC servo card failure
Triage note: B-65285EN 3.2.12: replace the COP10B cable first, then the SVM nearest the CNC, then the CNC servo card. Brief U blink at power-on followed by steady '-' is normal, not a failure.
Replacement parts
We supply the following units for this alarm — tested, warranty-backed:
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COP10A/B FSSB optical fiber cable
FSSB Optical Fiber Cable · Primary suspect
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A06B-6114-H2xx
Servo Amplifier Module αiSVM (unit nearest CNC showing U) · Common cause
Need the part urgently?
Send us alarm U with your machine details — typical RFQ turnaround is 24–48h.