15.07.2025 by Viktor Siebert

A Yaskawa SGDH-50DE servopack at an Italian customer (a medium-sized furniture manufacturer) repeatedly reported alarms A.71 and A.72. At first, the customer suspected material issues or high ambient temperatures. Since the machine only failed occasionally and could be restarted without issue, the customer decided to postpone the overhaul until the holiday break.

Sudden Complete Shutdown During Operation

Then, unexpectedly, the machine completely shut down. The servopack showed no reaction, and the LED status display remained off. A maintenance technician was called in and quickly diagnosed a motor-side short circuit. Upon inspection, he discovered the Yaskawa SGMGH-44DCA6H servomotor was severely contaminated with coolant emulsion. A serious short to ground had occurred.

Root Cause: Coolant Emulsion Inside the Motor

On the technician’s recommendation, the customer sent both units to us for inspection. Our analysis revealed the motor had absorbed approximately half a liter of fluid consisting of emulsion, oil, and metal chips. The seals were almost completely degraded, allowing the fluid to seep deep into the motor housing. Surprisingly, the system continued to operate under these conditions for quite some time.

Secondary Damage to the Drive Caused by Motor Failure

The contaminated motor ultimately caused the failure of the drive. After a detailed analysis, our senior technician concluded that the motor damaged the servopack. Fortunately, the SGDH-50DE was not as badly damaged as initially suspected. Only the transistor module and its driver circuitry were affected. Thanks to Yaskawa’s robust design, damage was limited by internal control and protection mechanisms.

Successful Refurbishment of Both Units

We performed a complete overhaul of both the motor and the drive. Just 7 days later, the customer reinstalled both units and was able to resume production without further issues.

Recommendation: Preventive Maintenance Avoids Failures

This case clearly shows the importance of regular inspection, especially in environments where machines are exposed to large volumes of coolant. What starts as a minor alarm can quickly escalate into a costly failure if ignored.

Our Standard Overhaul Process

1. Initial Assessment & Diagnostic Testing
   • Visual inspection
   • Functional and communication test
   • Documentation of all faults and anomalies
2. Disassembly & Cleaning
   • Complete disassembly
   • Ultrasonic cleaning
   • Removal of emulsions, oil, dust, and chips
3. Component Replacement & Repair
   • Replacement of defective and worn components
   • Repair or replacement of boards, power modules, encoders, bearings, and seals
4. Preventive Measures
   • Reinforcement of known weak points
   • Proactive replacement of components prone to failure
5. Final Assembly & Calibration
   • Assembly with new seals
   • Programming, parameter configuration, and fine-tuning

Our Testing Procedure

• Test run with original signal profiles
• Simulation of various load conditions
• Long-term stress testing (2–12 hours depending on unit)
• Test protocol and documented pass checklist

Here is the product page on our website:
Yaskawa SGDH-50DE AC Servopack

Servomotor Yaskawa SGMGH-44DCA6H

For more information about our Yaskawa SIGMA II Motor repair services, visit: Yaskawa Sigma II Servodrives

📞 Feel free to reach out if you have any questions regarding your Yaskawa servo motors or drives. Our team is here to help.

🔍 Note: The Yaskawa SGDH-50DE servo amplifier is commonly found in machines from the following manufacturers:

Morbidelli
Bavelloni
Busellato
Biesse
SCM Group
Paolino Bacci

If these machines begin to show recurring errors such as A.71, A.72 or A.C1, caution is advised, these are often early indicators of thermal stress or moisture-related damage to the drive or connected motor.

Device Specifications

Parameter	Value
Model	SGDH-50DE
Input Voltage (AC)	380–480 V, 3-phase, 50/60 Hz
Input Current	14.9 A
Output Voltage (AC)	0–480 V, 3-phase
Output Current	16.5 A
Output Power	5 kW / 6.71 HP
Protection Class	IP1X
Weight	Approx. 5.5–6.5 kg (based on similar models)
Manufacturer	Yaskawa Electric, Made in Japan

Functional Description

The SGDH-50DE is a servo amplifier (servopack) from the Sigma-II series, designed for precise position, speed, and torque control of Yaskawa AC servo motors.

Key Features:

• Supports analog and digital control signals
• PI / P control (switchable via /P-CON signal)
• Supports incremental and absolute encoders
• Configurable electronic gear (parameters Pn202 / Pn203)
• Integrated regeneration circuit (B1/B2) with optional external resistor
• Brake control via /BK signal

Alarm List & Troubleshooting

Alarm Code	Description	Possible Causes & Solutions
A.02	EEPROM data error	Restart controller, if persistent: replace drive
A.03	Encoder error (main circuit)	Check encoder connection, replace motor if needed
A.10	Overcurrent / Heatsink overtemperature	Check for overload, verify fan operation
A.30	Regeneration circuit failure	Internal resistor faulty or B1/B2 miswired
A.32	Regeneration overload	Use external resistor (e.g. JUSP-RAxx)
A.40 / A.41	Overvoltage / Undervoltage	Check power supply voltage, install filter if needed
A.51	Overspeed	Check Pn300 (Speed Reference Gain), isolate motor from load
A.71 / A.72	Overload (short/long duration)	Verify mechanical load, improve cooling
A.b1 / A.b2	A/D converter fault for speed/torque input	Internal failure, drive may need to be replaced
A.C1	Servo overrun	Check setpoints and activate safety circuit
A.F1	Power phase loss	One phase missing – check AC supply input

Internal Components

Assembly	Model Name	Part Number	Function
Control Board	SGDH-CA30EE	DF0300464-B0	Main logic, CPU
Power Board	SGDH-CB50DAY12	DF9203659-B0	IGBT output stage
Option Board	JUSP-NSxxx	–	Optional functionality expansion
Power Module	Power Section 50	–	Power delivery to motor terminals