The submitted Yaskawa SGDB-15VD produced Alarm A10 immediately whenever a motor rotation was commanded.
This alarm typically appears when the drive initializes successfully but does not receive stable feedback from the encoder or detects a phase mismatch between reference and feedback.

After the incoming inspection, the unit was opened for detailed examination. Slight oxidation was visible on CN2 pins, and the control PCB near the +5 V encoder supply showed discoloration. The board was thoroughly cleaned, and the connector pins were treated with contact cleaner. Insulation tests on the power section showed normal values.

Using a laboratory power supply, the logic voltages were verified (±12 V and +5 V stable). However, under simulated motor operation, the A10 alarm reappeared. Under the microscope, an intermittent trace beneath the differential receiver IC (SN75115) – responsible for the encoder’s A/B signals, was discovered.
The IC was desoldered, the tracks were inspected, and a new component was installed.

Following repair, the drive was tested on the bench using a Yaskawa SGMG-20A2AB AC servo Motor. The motor started immediately, current draw remained steady, and no alarm occurred. Several load cycles were performed over two hours without anomalies.

Subsequently, all power components were thermally checked, the output stage re-soldered, and electrolytic capacitors measured for ESR. The heatsink was cleaned, all mounting screws re-torqued, and new thermal pads applied.
A final full-load test using original performance curves confirmed proper operation and thermal stability.

Preventive Measures for the Customer

1. Clean ventilation paths and heatsinks every 6 months.
2. Inspect CN1 and CN2 connectors for oxidation or loosened pins.
3. Measure supply voltage and phase balance annually.
4. Route encoder cables separately from power lines.
5. In dusty or oily environments, install an auxiliary fan or filter.
6. Replace main electrolytic capacitors every 7–8 years to ensure long-term stability.

Conclusion

Alarm A10 in Yaskawa SGDB-series Servopacks commonly results from contact or feedback signal issues in the encoder path.
Regular cleaning, connector maintenance, and proper grounding prevent such malfunctions and guarantee reliable long-term operation in industrial environments.

Information about the mentioned Servopack: Yaskawa SGDB-15VD Servopack

Mentioned Motor: Yaskawa SGMG-20A2AB AC servo Motor

Further details on our Yaskawa repairs can be found here: Yaskawa Sigma 1 Repair

📞 Feel free to contact us if you have any questions regarding your Yaskawa drive technology. Our team will be happy to assist you.

Device Specifications

Operating Environment & Compatible Devices

The SGDB-15VD belongs to Yaskawa’s first-generation Σ-I Servopack line and is widely used in machine tools, handling systems, and automated production lines.
It is typically paired with motors of the SGMG-20A2AB Sigma I series, each equipped with an incremental encoder (2500–6000 PPR).
The unit operates on a 200 V AC supply and connects to control and encoder lines via CN1 and CN2 connectors.
The recommended ambient temperature range is 0 °C to +40 °C, with relative humidity up to 80 % (non-condensing).

Functional Description

The SGDB-15VD is a fully digital AC Servopack designed for precise torque, speed, and position control of AC servo motors.
It uses a transistor-based PWM power stage to generate three-phase sinusoidal currents proportional to the reference input voltage.
Feedback from the incremental encoder (CN2 interface) closes the control loop, ensuring accurate and dynamic regulation.
The drive includes comprehensive protection features against over-current, over-voltage, over-temperature, phase loss, logic faults, and encoder communication errors.
A dynamic braking circuit is integrated and automatically activated in case of emergency stop or alarm.
The internal control electronics operate on ±12 V and +5 V rails that drive the IGBT gates, continuously monitored for consistency.

Alarm Codes & Troubleshooting

Main Components