Fanuc alarm 926: FSSB ALARM
system alarm · Fanuc 0i-D
What it means
Fatal error on the FSSB (fiber servo serial bus) between CNC and amplifiers at power-up
Likely causes
- broken/dirty optical fiber cable
- amplifier not powering up (blown PSU)
- wrong amplifier power-up order
- FSSB interface failure on main board
Triage note: Check DGN 000/axis screen for which slave dropped; swap suspect fiber between two working axes before replacing any amplifier
Replacement parts
We supply the following units for this alarm — tested, warranty-backed:
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A02B-0200-F311
FSSB Optical Fiber Cable · Primary suspect
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A06B-6130-H006
Power Supply Unit (beta i PSU) · Common cause
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A20B-8200-0740
Main CPU Board (0i-D) · Check if others ruled out
Need the part urgently?
Send us alarm 926 with your machine details — typical RFQ turnaround is 24–48h.