What the SRVO-221 alarm means

The controller does not detect the DSP (servo control) for the specified axis - the axis control card is missing, not seated, or failed. This is one of the most common faults in our repair logs for the FANUC R-30iA / R-30iB / R-30iB Plus platform, and the first inspection typically locates the cause.

Most common causes

  • Axis control card not seated properly (after transport or service)
  • Axis control card failure
  • Backplane/connector damage
Field note: Field experience says the first cause is the most likely — verify it before moving on to the rest.

Step-by-step field fix

  1. Power off, reseat the axis control card
  2. Check card edge connectors for contamination
  3. Swap the card to confirm before ordering a replacement
Safety first: For FANUC srvo-221, amplifiers and boards are live parts: hot-plugging a board burns interface circuits, and body static can kill sensitive devices. On site you may look at after confirming power-off the first step yourself: Power off, reseat the axis control card. Beyond that it is live boards and power devices work - leave it to a professional.

How we diagnose amplifier/hardware alarms on site

FANUC srvo-221 belongs to the amplifier & hardware family. On FANUC srvo-221 the failing stage is alpha-i / beta-i servo amplifiers with PSM supply modules and SVM servo modules (SPM where spindles fit) on the R-30iB Plus / R-30iB Mate Plus / R-30iA - the amplifier and drive hardware itself plus its periphery: boards, fuses, cooling, supply, connectors and self-test. We start reading FANUC srvo-221 at the iPendant ALARM screen (SRVO / MOTN / SYST / INTF prefixes) together with the amplifier's 7-segment status code.

The chain involved in FANUC srvo-221 runs: control-side signal -> amplifier board (drive and sense circuits) -> fuses and supply -> cooling -> motor-side output.

When FANUC srvo-221 fires, clear the external causes first - Many hardware alarms are not hardware at all but external conditions: a packed filter causing over-temperature, a missing phase causing undervoltage, a loose connector causing a communication drop. Our order clears the externals first - clean, replace the mat, measure supply, re-seat terminals - near-zero cost and a high hit rate. Only when externals are gone do we judge boards or power stage. It also keeps the quotation honest: we do not sell parts we have not earned.

Field notes on this page cover FANUC srvo-221 (Lack of DSP (Axis)); written by the Henghuan repair team, updated 2026-10-01.

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Related Amplifier & Hardware alarms

SRVO-057 — FSSB Disconnect SRVO-068 — DTERR - Data Transmission Error SRVO-069 — CRCERR - CRC Error SRVO-071 — SPHAL - Soft Phase Alarm SRVO-072 — PMAL - Pulse Coder Phase Alarm SRVO-073 — CMAL - Pulse Coder Count Error
Same family: this code belongs to the Amplifier & hardware alarms family - the page collects all Amplifier & hardware-family codes we have handled, with the common inspection order and spares.
Other brands: see our KUKA, ABB, Yaskawa and Universal Robots field-fix libraries — or the full 10-brand hub.

Frequently asked questions

QWhat does the FANUC srvo-221 alarm mean?

The controller does not detect the DSP (servo control) for the specified axis - the axis control card is missing, not seated, or failed. This is one of the most common faults in our repair logs for the FANUC R-30iA / R-30iB / R-30iB Plus platform, and the first inspection typically locates the cause. FANUC srvo-221 sits in the amplifier & hardware family; on our work orders the highest-frequency trigger for this code is "Axis control card not seated properly (after transport or service)".

QCan I clear a FANUC srvo-221 alarm myself?

Whether FANUC srvo-221 clears on its own depends on the outcome of "Power off, reseat the axis control card". Finish the flow with "Swap the card to confirm before ordering a replacement" to confirm FANUC srvo-221 - do not skip it. If that step is clean, the second most frequent cause on FANUC srvo-221 is "Axis control card failure". Two attempts and still there means stop: FANUC srvo-221 involves live boards and power devices, and running FANUC srvo-221 on can turn a repairable fault into a replacement.

QFor hardware alarms like FANUC srvo-221, does it always mean an expensive part swap?

The commonest causes we see on FANUC srvo-221 are "Axis control card not seated properly (after transport or service), Axis control card failure, Backplane/connector damage", so we stock the van against those. For FANUC srvo-221 specifically, we carry fuses, filter mats, common connectors and terminals; boards are stocked by type or go through the repair channel. For FANUC srvo-221, on hardware alarms we inspect before quoting - we do not open with replace the power stage. Before we roll, tell us what FANUC srvo-221 shows on the iPendant ALARM screen (SRVO / MOTN / SYST / INTF prefixes) together with the amplifier's 7-segment status code and what the machine was doing - phone or video triage is free.

This page on FANUC srvo-221 was compiled from actual repair records of the Henghuan Robotics repair team. Alarm notes are our own summary for troubleshooting reference only and may vary with controller and software version — please consult FANUC documentation or contact us if in doubt. Henghuan is an independent service provider, not affiliated with or endorsed by FANUC.