What causes FANUC alarm 930?

Faulty or loosely seated CPU board causing abnormal interrupt signals. Defective servo amplifier card generating electrical noise or spurious interrupts. Power supply voltage instability or ripple affecting CPU operation. Corrupted or failing RAM/ROM memory on the main CPU board. Electrical interference or grounding issues disrupting CPU signal integrity.

How do I fix FANUC alarm 930?

1. Power down the machine completely, then reseat the CPU board and all servo cards by firmly pressing them into their slots and securing any retaining hardware. 2. Check all power supply voltages with a multimeter to confirm they are within spec. Look for fluctuating or low DC voltages that could destabilize the CPU. 3. Inspect all ground connections on the control cabinet and machine frame. A loose or corroded ground is a common source of electrical noise that triggers this alarm. 4. Power the machine back on and note if the alarm appears immediately or only during specific operations like axis movement or spindle start, as this helps isolate the faulty card. 5. If the alarm persists after reseating boards, swap the CPU board or servo card with a known good spare if available, then contact Fanuc service with the alarm history for further diagnosis.

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FANUC Controller

System · Advanced · 1-4 hours depending on root cause

Alarm 930

Fanuc Alarm 930 - CPU INTERRUPT

Fanuc Alarm 930 CPU INTERRUPT indicates an abnormal interrupt signal was received by the main CPU board, typically caused by hardware faults or communication breakdowns between the CNC and connected modules. This is a critical system alarm that points to loose connections, failing boards, or electrical noise interference on the control backplane.

FANUCSystemAdvanced1-4 hours depending on root cause

930

Fanuc Alarm 930 - CPU INTERRUPT

CPU Error

Root Cause Summary

Fanuc Alarm 930 CPU INTERRUPT indicates an abnormal interrupt signal was received by the main CPU board, typically caused by hardware faults or communication breakdowns between the CNC and connected modules. This is a critical system alarm that points to loose connections, failing boards, or electrical noise interference on the control backplane.

Safety

System unstable
Contact service
Electrical Hazard: Power down and disconnect the machine from the main power supply before performing any internal checks or component replacements. Lockout/Tagout procedures should be followed.
Mechanical Hazard: Be aware of potential moving parts if accessing internal components while the machine is partially powered. Ensure all safety interlocks are functioning correctly.
Electrostatic Discharge (ESD) Hazard: Use proper ESD precautions (e.g., grounding straps) when handling electronic components.
System is unstable and may cause injury or damage; Ensure personal safety and wear protective gear
⚠️ MECHANICAL HAZARD: Verify safety interlocks function before accessing internal components.
⚠️ ESD HAZARD: Use proper grounding straps when handling electronic components.
High Voltage Hazard: Be aware of high voltage components within the control cabinet. Only qualified personnel should access these areas.
Crush Hazard: Ensure machine is properly supported and secured before accessing internal components to prevent accidental movement.

Causes and Fixes

1
Power down the CNC completely and discharge capacitors (wait 5 minutes minimum). Open the control cabinet and locate the main CPU board (typically slot JD1A on 0i/30i/31i/32i series controls).
Electrostatic discharge can destroy CPU boards. Use proper ESD wrist strap grounded to cabinet frame.
2
Remove and carefully reseat the main CPU board, FROM/SRAM board, and all axis control boards (slot designations vary: check JD1A, JD1B, JA40, JA7B). Ensure connector clips are fully engaged and boards are perpendicular to backplane.
3
Inspect backplane connectors for bent pins, corrosion, or carbon tracking. Clean contacts with 99% isopropyl alcohol and lint-free cloth if contamination is visible.
4
Power up and monitor for alarm recurrence. Navigate to SYSTEM > DIAGNOSIS > #0200-#0299 (system diagnostic data) to check for additional fault codes that may indicate which board caused the interrupt.

Service Recommendedmedium confidence

Call a technician if:

·CPU board replacement needed
·Multiple diagnostic tests fail
·Alarm persists after basic troubleshooting
·System software reload required

Prevention

Maintain proper cabinet ventilation and temperature
Replace backup battery every 2-3 years
Perform regular power quality monitoring
Keep system software and parameters backed up
Schedule periodic connector cleaning and reseating

Common Mistakes

Ignoring power quality issues
Not checking battery voltage during troubleshooting
Attempting to continue operation with intermittent CPU errors
Failing to backup parameters before system reset
Not verifying proper grounding during installation

Related Alarms

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Always verify with your machine manual or a certified technician before performing service procedures.