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Check DC link voltage at DIAGNOSIS > SERVO > DC LINK screen. Verify L-N voltage readings for all three phases (R, S, T). Normal DC link should read approximately 1.35x line-to-line AC voltage (280-310VDC for 200V class, 540-580VDC for 400V class).

Measure incoming AC voltage at power supply module input terminals L1, L2, L3 with voltmeter. Verify balanced three-phase voltage within 2% tolerance. Check for loose connections, damaged contactors, or blown fuses in distribution panel.

Use appropriate PPE and lockout/tagout procedures when measuring high voltage AC power

Monitor AC voltage under dynamic load conditions during rapid traverse and acceleration. Voltage drop exceeding 10% indicates inadequate supply capacity, undersized wiring, or high impedance connections. Check branch circuit breaker rating matches amplifier requirements.

Inspect PSM (Power Supply Module) LED indicators. Steady red or flashing LED patterns indicate input power faults. Check alarm history at DIAGNOSIS > ALARM HISTORY for related alarms (400, 401, 414) indicating power supply issues.

Check DC link ripple voltage at DIAGNOSIS > SERVO > DC LINK screen during axis motion. Excessive ripple (>15V peak-to-peak for 200V class, >30V for 400V class) indicates capacitor degradation. Compare readings during idle vs. heavy cutting loads.

Inspect DC link capacitors inside αi/βi servo amplifier for physical damage: bulging tops, electrolyte leakage, or discoloration. Document installation date from amplifier label. Capacitors typically require replacement every 7-10 years depending on ambient temperature and duty cycle.

Disconnect all AC power and wait 15 minutes minimum for DC bus discharge before opening amplifier covers

Measure DC bus capacitance using capacitance meter if accessible (requires amplifier disassembly). Compare to nameplate specifications. Capacitance below 80% of rated value requires replacement. Typical values: 2200-4700µF for compact amplifiers, higher for larger modules.

Only qualified personnel should perform internal amplifier measurements

Review parameter 8166 (DC link voltage detection level) to verify threshold settings have not been improperly modified. Default values should not be changed without factory authorization. Reset to default if adjusted: 240VDC for 200V class, 480VDC for 400V class.

Check regenerative discharge resistor connections and resistance values. Measure resistance across discharge resistor terminals (typically 20-80 ohms depending on amplifier capacity). Open circuit or significantly increased resistance indicates resistor failure or connection loss.

Ensure DC bus is fully discharged before measuring regenerative resistor

Verify discharge transistor operation by monitoring DC link voltage during rapid deceleration at DIAGNOSIS > SERVO > DC LINK screen. Voltage should remain stable. Excessive voltage swing (>50V) indicates regenerative circuit malfunction. Check amplifier LED for regen fault codes.

Inspect wiring between amplifier and external regenerative resistor unit (if equipped). Verify tight connections at both amplifier terminals and resistor box. Check for burned terminals, corroded connections, or damaged cables that increase circuit resistance.