Fanuc alarm SV0401: SERVO V-READY OFF
0i-D servo alarm (ready signal) · Fanuc 0i-D
What it means
Position ready (PRDY) commanded ON but amplifier speed-ready (VRDY) did not come ON, or dropped during operation
Likely causes
- servo amplifier internal failure (classic dead-SVM symptom)
- MCC contactor not closing / e-stop chain open
- +24V control feed to amp missing
- converter (PSM) alarm cascading to axes
Triage note: Read DGN 358 bit pattern to split causes: MCC/e-stop wiring vs amp hardware; amp LED showing '-'/'AL' confirms amplifier replacement
Replacement parts
We supply the following units for this alarm — tested, warranty-backed:
- Request a quote →
A06B-6134-H303
Servo Amplifier Unit (beta i SVM) · Primary suspect
- Request a quote →
A06B-6240-H206
Servo Amplifier Module (alpha iS SVM) · Primary suspect
- Request a quote →
A06B-6130-H006
Power Supply Unit (beta i PSU) · Common cause
Need the part urgently?
Send us alarm SV0401 with your machine details — typical RFQ turnaround is 24–48h.