SV0434

Check Control Voltage Readings

Navigate to the DIAGNOSIS screen (System > Servo > Monitor) and record the control voltage for the faulted axis. It should be 24VDC ±10%. A significantly lower value indicates internal circuit failure.

Compare the voltage reading with other axes to identify if the issue is isolated to this amplifier.

Ensure the machine is powered down and locked out before proceeding to physical inspection.

Inspect Amplifier Control Board

Power down the machine, apply LOTO, and remove the servo amplifier cover. Visually inspect the control board for bulging capacitors, burn marks, or cracked traces that could indicate a failure in the voltage regulation circuit.

Use a magnifying glass to spot micro-cracks or subtle discoloration on the board.

Wait at least 5 minutes after power-down and verify no residual voltage with a multimeter before touching components.

Test with Replacement Amplifier

If damage is suspected or voltage is out of spec, swap the amplifier with a known-good unit of the same model. Transfer necessary parameters and test the axis. If the alarm clears, the original amplifier is defective and needs repair or replacement.

Document all parameter settings before swapping to ensure proper configuration of the replacement unit.

Incorrect parameter settings during swap can cause unexpected axis motion. Double-check settings before power-up.

Measure Voltage at CN1 Connector

Power down the machine, apply LOTO, and use a multimeter to measure the voltage at the CN1 connector pins (PC and DCM) on the servo amplifier. Ensure it reads 24VDC ±10% when powered back up under no-load conditions.

Wiggle the connector slightly during measurement to detect intermittent voltage drops due to loose contacts.

Ensure no power is present before accessing the connector to avoid electrical shock.

Inspect Connector Terminals

Visually inspect the CN1 connector for corrosion, bent pins, or heat damage. Clean the terminals with electrical contact cleaner if corrosion is present, and reseat the connector firmly.

Use a small brush to remove debris from connector pins for a thorough cleaning.

Do not use excessive force when reseating connectors to avoid damaging pins.

Retest After Repair

After cleaning or reseating, power up the machine and recheck the control voltage at the DIAGNOSIS screen. Jog the axis at low speed to confirm the alarm does not reappear under light load.

Monitor voltage stability over a few minutes to catch intermittent issues.

If the alarm persists, do not operate the machine under load until the root cause is resolved.

Visual Inspection for Capacitor Damage

Power down, apply LOTO, and open the servo amplifier. Look for bulging, leaking, or discolored capacitors on the control board, especially near the low-voltage section.

Take photos of the board before disassembly to aid in reassembly or for documentation.

Wait 5 minutes after power-down and confirm no residual voltage before inspection.

Test Voltage Stability

Power up the machine and monitor the control voltage on the DIAGNOSIS screen over a 5-10 minute period. Fluctuations or gradual drops suggest failing capacitors unable to maintain steady voltage.

Use a data logger if available to capture subtle voltage fluctuations over time.

Avoid running the machine under heavy load during this test to prevent further damage.

Replace Faulty Capacitors or Amplifier

If capacitors are visibly damaged or voltage is unstable, replace the affected capacitors if you have the expertise, or replace the entire amplifier. Retest the system after replacement to confirm resolution.

Ensure replacement capacitors match the original specs (voltage rating and capacitance) to avoid mismatches.

Improper soldering during capacitor replacement can damage the board. Consider professional repair if unsure.

Check DC Bus Voltage

Access the DIAGNOSIS screen (System > Servo > Monitor) and record the DC bus voltage for the faulted axis. Ensure it is within spec (280-320VDC for 200V class, 510-670VDC for 400V class).

Compare readings during idle and under load to detect transient drops.

Do not attempt physical repairs without proper LOTO procedures.

Inspect Regenerative Discharge Unit

Power down, apply LOTO, and inspect the regenerative discharge resistor or unit connected to the power supply module (PSM). Look for burn marks, overheating, or disconnected wiring.

Use a thermal camera if available to spot overheating components before physical inspection.

High voltages are present in this area. Wait 5 minutes and verify zero voltage before touching.

Test PSM Output

If the regenerative unit appears normal, test the output stability of the power supply module (PSM) feeding the amplifier. If out of spec, the PSM may need repair or replacement. Retest the system after addressing the issue.

Consult the PSM manual for specific voltage test points and procedures.

PSM repairs often require specialized skills. Escalate to a technician if unsure.

Check Cooling Fan Operation

Power up the machine and observe if the cooling fans on the servo amplifier are spinning. Listen for unusual noises or weak airflow that could indicate fan failure.

Feel for airflow with your hand (from a safe distance) if visual confirmation is unclear.

Do not touch moving fans or internal components while the machine is powered.

Inspect Heat Sink Condition

Power down, apply LOTO, and inspect the heat sink on the amplifier for dust, debris, or blockages. Clean with compressed air or a soft brush if necessary to ensure proper heat dissipation.

Use a vacuum with a brush attachment to avoid pushing debris deeper into the unit.

Ensure no power is present before cleaning to avoid electrical hazards.

Monitor Temperature and Retest

After cleaning, power up and monitor the amplifier temperature (if a sensor reading is available) or feel the heat sink after a short operation period. Retest the axis under load to confirm if the alarm persists.

Consider adding external cooling or improving machine room ventilation if overheating recurs.

Persistent overheating may indicate internal component stress. Avoid prolonged operation until resolved.