Yaskawa Servo Pack Alarm List: Causes, Troubleshooting & Repair Guide

1. What Are Yaskawa Servo Pack Alarms?

Yaskawa servo packs (servo drives) continuously monitor system conditions in real time.
When abnormal behavior is detected, the drive generates an alarm code to protect hardware and prevent secondary damage.

These alarms typically indicate issues in:

• Power stage / internal electrical circuits
• Mechanical load conditions
• Encoder / feedback signals
• Communication or control logic

Important:
A servo alarm is not the root cause—It is a protective response triggered somewhere in the system chain.

2. Most Common Yaskawa Servo Pack Alarm Codes

Th is page covers the most frequently encountered servo pack alarms in industrial applications.

🔹 A.710 – Overcurrent Alarm

See full guide: Yaskawa A.710 Overcurrent Alarm

Meaning: Output current exceeds safe limits

Typical causes:

• Motor or cable short circuit
• Internal IGBT degradation (servo drive)
• Sudden mechanical shock or lock

Insight: Persistent A.710 often indicates internal drive failure.

🔹 A.720 – Overload Alarm

See full guide: Yaskawa A.720 Overload Alarm

Meaning: Excessive torque demand over time

Common causes:

• Gearbox binding or reducer wear
• Increased friction (bearings)
• Motor undersized for load

🔹 A.810 – Encoder Error

See full guide: Yaskawa A.810 Encoder Error

Meaning: Feedback signal lost or unstable

Typical causes:

• Encoder cable internal breakage
• Connector oxidation
• EMI interference

Field data: Most cases are cable-related.

🔹 A.820 – Regenerative Error

Meaning: Regenerative energy cannot be dissipated

Common causes:

• Braking resistor failure
• Excessive deceleration energy
• Internal DC bus instability

🔹 A.840 – Overvoltage Alarm

Meaning: DC bus voltage exceeds safe limits

Typical causes:

• Aggressive deceleration
• Unstable input power
• Drive voltage sensing failure

Key Insight:
While alarms appear different, many failures originate from the same upstream components—especially the servo drive.

3. Root Cause Mapping of Yaskawa Servo Pack Alarms

Diagnostic Rule:

If alarms persist across different conditions → Servo Drive is the primary suspect

4. How to Troubleshoot Yaskawa Servo Pack Alarms

Use a structured isolation process to avoid unnecessary component replacement.

Step 1 – Identify the Alarm Code

Record the exact alarm number and frequency of occurrence.

Step 2 – Determine Operating Condition

• Startup failure → electrical or internal drive issue
• Motion-triggered alarm → load or feedback issue

🔥 5-Minute Drive Isolation Test

Disconnect motor and external load, then power the drive:

• Alarm persists → Servo drive failure likely
• Alarm disappears → External component issue

This is one of the fastest methods to isolate servo drive failure.

Step 3 – Check Power and Wiring

• Verify input voltage stability
• Inspect grounding quality
• Check terminal and cable integrity

Step 4 – Evaluate Mechanical Load

• Check for mechanical binding
• Verify torque demand consistency
• Inspect gearbox and coupling condition

Key Diagnostic Patterns Across Yaskawa Servo Alarms

• Multi-axis similar alarms → shared drive or power issue
• Intermittent alarms → cable or connector degradation
• Persistent alarms without load → internal drive failure

5. Components That Commonly Cause Yaskawa Servo Pack Alarms

After isolation, faults typically converge to one of the following components:

Servo Drive

Primary suspect when:

• Alarms persist without load
• Multiple unrelated alarms appear
• System fails isolation test

Servo Motor

Required when:

• Winding imbalance is detected
• Mechanical resistance is abnormal

Encoder Cable

Common failure point when:

• A.810 appears intermittently
• Signal loss varies with motion

In electrical alarm cases, servo drive failure is the most frequent root cause after external components are excluded.

6. Recommended Solutions for Yaskawa Servo Alarms (Drives, Motors & Cables)

When troubleshooting servo-related alarms, selecting the correct repair path is critical to avoid unnecessary downtime and replacement costs. Below are the most effective solutions basedon real-world failure scenarios:

• Servo Drive Replacement
  If your system is showing persistent electrical alarms such as A.710 or A.840, or multiple alarms appearing simultaneously, the issue is often rooted in the servo drive itself. In cases where insulation or isolation tests fail, it strongly indicates internal electrical breakdown.
  → Learn when and how to replace the servo driveto restore stable operation.
• Servo Motor Replacement
  When abnormal load, resistance, or overheating is detected, the problem is typically mechanical rather than electrical. Damaged windings or internal motor wear can also trigger overload conditions.
  → See how to properly replace the servo motorand prevent recurring overload faults.
• Encoder Cable Replacement
  Unstable feedback signals, intermittent positioning errors, or encoder-related alarms often point to communication issues rather than hardware failure. In many cases, worn or damaged cables are the root cause.
  → Check th is guide to replace the encoder cableand resolve feedback instability.

All replacements should be validated under real load conditions.

7. Repair vs Replacement Decision Guide

Repair

• Lower upfront cost
• Suitable for minor connector or external issues
• Higher risk of recurrence in aging systems

Replace

• Faster system recovery
• Stable long-term operation
• Reduced unplanned downtime risk

Decision Insight

If alarms persist after external checks and isolation tests, the servo drive is typically beyond stable recovery through repair.

In production environments, repeated alarm events usually cost more in downtime than the replacement hardware itself.

FAQ

What is the most common servo pack failure?

Servo drive internal degradation is the most frequent cause in aging systems.

Can alarm codes be cleared without fixing the issue?

No. Alarms will return if the root cause remains unresolved.

How do I confirm servo drive failure?

If alarms persist after isolation tests, the drive is the likely failure point.

Are encoder errors always cable-related?

Most are cable-related, but severe cases may involve drive interface failure.

When should the servo drive be replaced?

When internal electrical faults persist after all external components are verified.