Fanuc alarm 502: NOISE ON POWER SUPPLY
30i/31i/32i system alarm · Fanuc 30i/31i/32i-B
What it means
The CNC detected a power anomaly consistent with noise or an instantaneous power failure on its 24V DC input, and halted to protect SRAM data. Fanuc warns this event can damage SRAM contents, so verify parameters and part programs after clearing it. Finding and removing the electrical cause is the remedy - replacing boards rarely helps.
Likely causes
- Instantaneous power loss or severe sags on incoming supply
- Missing/poor earth grounding allowing conducted noise
- Contactors or welders sharing the same supply branch without suppression
Triage note: Alarm 503 (ABNORMAL POWER SUPPLY, MAIN BOARD) is raised when the onboard supply itself is judged faulty.
Need the part urgently?
Send us alarm 502 with your machine details — typical RFQ turnaround is 24–48h.