FANUC SRVO-280 SVOFF Input Alarm
What SRVO-280 Means
SRVO-280 appears on the teach pendant and in the alarm log as “SERVO SVOFF input.” The controller has detected that the SVOFF (servo-off) signal was asserted. SVOFF is a safety-related input designed to remove servo power whenever it is activated, so the alarm text simply reports that this input was received, not what triggered it.
When SRVO-280 is active, servo power is off and the robot cannot move until the input is cleared and the alarm is reset. This behavior applies to FANUC R-30iA and R-30iB/R-30iB Plus controllers configured with an SVOFF input.
Common Causes And Companion Alarms
SRVO-280 is a signal-state alarm, not a component-failure code, so start with the external circuit before suspecting hardware. In order of likelihood:
An open or tripped safety device in the SVOFF path — emergency-stop button, gate/interlock switch, light curtain, or safety relay contact — is the most common cause. Next is a PLC output, delivered through UOP or peripheral I/O, that is sitting in the servo-off state, intentionally or due to a logic fault. Related is the *IMSTP input, which is normally on; if it turns off, it generates its own alarm and also removes servo power. Wiring faults — an open conductor, loose terminal, failed relay contact, misadjusted gate switch, or defective e-stop contact — can produce the same symptom. Internal controller hardware is a possible cause only after the external wiring and devices are verified correct.
- SRVO-281 (SYSTEM SVOFF input, SVEMG abnormal): SVOFF detected together with an SVEMG disconnection or emergency-circuit fault.
- SRVO-282 (SERVO Chain 1 SVOFF abnormal): fault in the +24V safety chain feeding the SVOFF circuit.
- SRVO-283 (SERVO Chain 2 SVOFF abnormal): fault in the 0V safety chain feeding the SVOFF circuit.
Step By Step Troubleshooting
Follow lockout/tagout procedures before opening the controller cabinet or working on field wiring.
1. Record the full alarm text and alarm history — all SRVO, SYSTEM, and safety alarms — before cycling power, since companion codes point to the specific chain or circuit involved.
2. Note the axis/group affected and what the robot was doing when the alarm occurred.
3. With power under controlled conditions, inspect the external safety circuit: e-stop buttons, gate switches, light curtains, and safety relays for open or damaged contacts.
4. Trace the PLC-controlled safety output and the UOP/peripheral I/O wiring feeding the SVOFF or *IMSTP circuit back to the field device.
5. Check continuity, correct voltage, and contact operation along that path, and confirm agreement between redundant channels if SRVO-282 or SRVO-283 is also present.
6. Do not bypass or jumper SVOFF, SVEMG, e-stop, or safety-chain wiring at any point.
Clearing And Resetting SRVO-280
The documented recovery for SRVO-280 is to identify and remove the cause of the SVOFF input, then press RESET on the teach pendant. If the alarm will not clear, the controller maintenance manual directs troubleshooting of the associated SVOFF components rather than a repeated reset attempt.
Companion alarms have their own documented steps. For SRVO-281, turn controller power off, repair the SVEMG wiring, close the SVOFF input circuit, and press reset. For SRVO-282 or SRVO-283, repair the Chain 1 (+24V) or Chain 2 (0V) circuit in the SVOFF hardware, enable chain-fault reset in system settings where required, and press the teach-pendant reset key.
After any reset, confirm the SVOFF input is in its normal state, enable servo power, and re-operate the relevant e-stop and protective devices to confirm they still produce the expected servo-off response before returning the robot to production.
When It Points To Hardware
If the external wiring, safety devices, PLC output, and UOP/peripheral I/O all check out correct and SRVO-280, SRVO-281, SRVO-282, or SRVO-283 still will not clear, the cause is likely inside the controller: an input board, emergency-stop unit, safety relay, or an internal fault in the SVOFF circuit itself.
To tell the difference, test the SVOFF circuit for continuity, correct voltage, proper contact operation, and agreement between the redundant safety chains. If those pass on the external side but the fault persists or the chains disagree inside the cabinet, the issue is internal hardware rather than field wiring.
Because SVOFF hardware differs across R-30iA, R-30iB, and R-30iB Plus controllers, confirm the exact controller variant, software revision, alarm history, I/O configuration, and electrical schematic before any board or emergency-unit repair is quoted.
How Robotics Integration Helps
Robotics Integration works SRVO-280 calls by phone and video to walk through the alarm history, the SVOFF/UOP/PLC wiring path, and the safety-device checks described above, so a maintenance team can narrow the cause before deciding whether the fix is wiring, a field device, or controller hardware.
When the fault traces to the controller, Robotics Integration handles component-level repair of the affected boards, safety relays, or emergency-stop units for R-30iA, R-30iB, and R-30iB Plus systems, and provides on-site service when wiring repair, safety-circuit verification, or hands-on diagnosis is needed beyond what remote troubleshooting can resolve.
All work follows the documented procedures for SVOFF, SVEMG, and Chain 1/Chain 2 alarms — no bypassing of safety circuits, and no repair recommendation made without first confirming the exact controller model and configuration.
Looking up a different code? See the full FANUC and robot alarm code list, or read about our FANUC robot repair.
Get Help With This Alarm Now
To get a fast, accurate read on an SRVO-280 alarm, have the following ready before calling: the controller model (R-30iA, R-30iB, or R-30iB Plus), the exact alarm text and full alarm history, the axis or group affected, what the robot was doing when the alarm occurred, and a description of the connected safety devices, PLC outputs, or UOP wiring involved.
With that information, a technician can start isolating whether the SVOFF condition is coming from an external safety device, a PLC or UOP signal, field wiring, or internal controller hardware — and whether a companion alarm such as SRVO-281, SRVO-282, or SRVO-283 changes the repair path.
Call Robotics Integration at 1-602-449-1556 to walk through the alarm with a technician and get the unit moving again.
Talk A Robotics Integrator
By submitting this form, you agree to receive communications via phone, text message, and email. Message and data rates may apply. Your information may be shared with trusted third-party service providers solely for the purpose of helping you explore Section Robotic Intergration options. You also agree to our Privacy Policy and Terms of Service.
+1 602-449-1556
Success Stories: See What Business Have To Say About Robotics Integration
4.7 Customer Reviews
