SV0004

Check amplifier LED status: AL LED solid red indicates alarm state, CHARGE LED off indicates DC bus not charged. Verify input voltage is 200-230VAC (single phase) or 200-230VAC 3-phase depending on PSM model.

Navigate to DIAGNOSIS > SERVO and check DC link voltage (parameter display varies by series, typically #300-#307 for axis diagnostic data). Verify DC bus reads 280-320VDC. Below 250VDC indicates power supply module (PSM) failure or input power issue.

Inspect regenerative discharge resistor connections and resistance value. Check PSM alarm history by accessing SYSTEM > ALARM > HISTORY and look for PS000 series alarms indicating PSM faults prior to SV0004.

If DC bus voltage is low, verify proper ground connections to amplifier frame and check for blown fuses on input AC lines. Replace PSM if DC bus fails to reach 280VDC within 2 seconds of power-on.

HIGH VOLTAGE: Wait 5 minutes after power-off and verify DC bus voltage is below 50VDC before servicing

Check amplifier LED codes: READY LED off with AL LED solid indicates internal fault. For αi series amplifiers, refer to the seven-segment display code. Navigate to DIAGNOSIS > SERVO > SV ALARM to identify specific amplifier alarm code (may show alongside SV0004).

Verify optical fiber or FSSB (high-speed serial bus) cable connections between CNC and amplifier. Check for damaged cables, loose connectors at both CNC JD1A/JD1B ports and amplifier CN1/CN1A ports. LED indicators on fiber connectors should show data transmission (flickering).

Access MAINTENANCE > SERVO > PARAMETER and verify axis assignment parameters match physical configuration: check parameter 1020 (serial spindle/servo specification) and parameters 1022-1025 (axis number assignment). Mismatch causes amplifier not detected.

If amplifier shows internal fault code (AL LED with specific code), power cycle the system. If SV0004 persists immediately on power-up with same amplifier, replace the servo amplifier module. Document amplifier serial number and fault code for warranty/service records.

Verify emergency stop circuit is released: check that E-STOP button is disengaged and *ESP signal is present. Navigate to DIAGNOSIS > PMC > STATUS > G and verify machine enable signals (typically X0.0 for servo ready enable). Signal must be '1' for amplifiers to enable.

Check parameter 1815 #0 (servo off detection) and parameter 1802 (servo off detection time). Incorrect settings may cause CNC to fault before amplifier completes initialization. Default 1802 should be 200-500ms. Set parameter 1815 #0 = 0 to enable detection.

Verify amplifier type parameters: check parameter 1815 #1 (amplifier selection - 0=α series, 1=αi series), parameter 1820 (serial number for each axis), and parameter 1825 (servo motor model code). Mismatch between parameter and physical amplifier prevents ready signal.

Perform controlled power cycle: turn off CNC, wait 2 minutes for full capacitor discharge, power on and monitor time from power-on to SV0004 alarm. If alarm occurs within 1-2 seconds, indicates communication fault. If after 5-10 seconds, indicates amplifier initialization failure requiring amplifier replacement.