602

Check amplifier cooling fan operation. With power on (alarm present), verify fan rotation visually and audibly. For αi/βi servo amplifiers, fan failure often coincides with alarm 602. Replace fan if not operating (typical part: A860-0104-Txxx series).

Ensure proper lockout/tagout before opening cabinet. High voltage present at amplifier terminals.

Inspect and clean/replace cabinet air filters. Check intake and exhaust filters for dust accumulation. Clogged filters reduce airflow by 50% or more, causing thermal buildup even with functional fans.

Verify ambient temperature around servo amplifier. Check DIAGNOSIS screen > SERVO > temperature monitoring (parameters 1611-1614 on 0i/30i/31i systems show servo amp temperature). Ambient should be ≤40°C (104°F) per Fanuc specifications. Use infrared thermometer to measure cabinet internal temperature.

Ensure minimum clearance around amplifier: 100mm (4 inches) above/below for ventilation per Fanuc installation manual. Check for adjacent heat sources (transformers, other amplifiers) that raise local ambient temperature.

Check servo load meter on DIAGNOSIS screen > SERVO > LOAD MONITOR. Navigate to SYSTEM > DIAGNOSIS > #300-#30x (axis-specific load). Normal operation should show <70% average load. Sustained loads >80% indicate mechanical binding or undersized motor/amplifier.

Verify axis moves freely by manual operation (servo off). Check for mechanical binding, damaged bearings, insufficient lubrication, or collision damage. Inspect ballscrews, linear guides, and coupling alignment.

Use MPG or handwheel mode for manual movement verification. Disable servo with EMG STOP accessible.

Review servo parameters for excessive gain settings. Check parameter 2021 (position loop gain), 2023 (velocity loop gain), 2022 (velocity integral time constant). Overly aggressive tuning increases current ripple and heat generation. Compare to Fanuc recommended values in servo motor parameter manual.

Monitor instantaneous current on DIAGNOSIS > SERVO > CURRENT display (#30x series diagnostics). Check against motor rated current (parameter 2134). If approaching or exceeding motor rated current during normal moves, investigate excessive cutting forces, rapid acceleration rates (parameters 1620-1623), or mechanical resistance.

Check amplifier LED status codes. Red LED steady or flashing patterns indicate internal faults. Refer to amplifier label for LED code interpretation (αi: AL LED, βi: 7-segment display). Document codes before reset attempts.

Evaluate machine duty cycle. If alarm occurs after specific repetitive operations, calculate actual duty cycle vs. rated. Check parameters 2012 (rated motor current) and compare to DIAGNOSIS #30x current readings during cycle. Reduce rapid reversal rates or implement dwell time if exceeding thermal capacity.

Verify regenerative discharge resistor operation if axis performs frequent deceleration or vertical axis lowering. Check parameter 2062 (regenerative discharge resistor alarm time). Measure DC bus voltage on DIAGNOSIS screen during deceleration - excessive voltage (>400V on 230V systems) indicates inadequate resistor capacity.

Do not measure DC bus voltage directly. Use diagnostic display only.

If amplifier is >7 years old and alarm is intermittent, consider preventive replacement or thermal compound renewal. Electrolytic capacitor ESR increases with age, reducing filtering effectiveness and increasing ripple heating. Contact Fanuc service for amplifier refurbishment or exchange program.