Code SV0433: Converter: DC link undervoltage
Issue Description & Safety Warning
The Fanuc Alpha-i Servo Spindle Amplifier has triggered a critical Converter: DC link undervoltage alarm. Immediate attention from a qualified operator or maintenance technician is required to prevent secondary damage to the equipment or spoiled parts during the manufacturing cycle. Always ensure standard safety and LOTO procedures are followed before accessing electrical cabinets.
Official Troubleshooting Steps
Amplifier LED display: 4 Also shown as: SV0433 (15i), SV0433 (30i/31i/32i), SV0433 (0i-D) Cause: (1) Meaning The temperature of the main circuit heat sink has risen abnormally. (2) Cause and troubleshooting (a) Cooling fan for the main circuit broken Check whether the cooling fan for the main circuit rotates normally. → Replace it. (b) Dust accumulation → Clean the cooling system with a vacuum cleaner or the factory air blower. (c) Overload → Examine the operating conditions. (d) Poor installation of the control printed-circuit board → Be sure to push the faceplate as far as it will go. (This alarm may be displayed if one of the connectors for connection between the control printed-circuit board and power printed-circuit board is detached.)
Source: Fanuc αi Servo/Spindle Amplifier Maintenance Manual (B-65285EN/04) — Part II Troubleshooting
Last reviewed: 2026-07-01 · Verified against the manufacturer’s official documentation.
About Fanuc Alpha-i Servo Spindle Amplifier Alarms
Fanuc controllers include extensive self-diagnostics that flag or halt the machine when a fault is detected. Error code SV0433 on the Alpha-i Servo Spindle Amplifier identifies one specific fault condition — its documented cause and the official corrective steps are listed above, sourced from Fanuc's service documentation. Always confirm against the manual for your exact machine configuration and follow LOTO procedures before servicing.
Complete Alarm List: 135 Fanuc Alpha-i Servo Spindle Amplifier codes.
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