The repair case described here concerns a Yaskawa SGDH-20EEY338 Servopack that was used in a Brother CNC machining center as the drive for the Y axis.
The unit was sent in with the fault description that the Y axis does not run smoothly, behaves irregularly especially when load is applied, and switches off with an overload alarm after a short increase in force. The problem was reproducible and clearly noticeable for the machine operator, as clean circular movements and uniform feed motions were no longer possible.

Initial Situation and Fault Symptoms

Even during the first functional check, abnormal axis behavior was evident. In no-load operation, slight irregularities could already be detected, and under load the problem became significantly more pronounced. The axis reacted with a delay, built up torque in a jerky manner, and responded to higher loads with an overload shutdown.
In practice, such symptoms are typical of a combination of control deviations, internal aging effects within the servopack, or faulty feedback signals, without an immediately obvious hard alarm being present.

Externally, the servopack showed no visible damage. Fan, heatsink, and connectors appeared intact, which initially made fault localization more difficult.

Diagnosis and Systematic Analysis

As with all axis-related issues, the fault was not viewed in isolation but analyzed in the interaction between mechanics, motor, encoder, cabling, and servopack.
After removal from the machine, an initial electrical baseline check was performed. Power supply, DC link voltage, and control signals were all within the expected ranges. However, during dynamic tests under load, clear abnormalities appeared in the current behavior of the axis.

The behavior during sudden load demand was particularly critical. Strong current fluctuations occurred, ultimately triggering the overload monitoring. Such behavior often indicates that the servopack is no longer able to regulate the required torque cleanly or that internal measurement values are no longer stable.

Internal Inspection of the Servopack

After opening the SGDH-20EEY338, a detailed visual and measurement inspection was carried out. A typical age-related condition became apparent, as is frequently observed in servopacks of this generation.
Certain assemblies responsible for accurate current measurement and control showed deviations. These deviations result in the servopack still functioning in principle, but making incorrect control decisions under dynamic load. The consequence is an irregular axis motion and premature overload tripping.

In highly dynamic CNC axes, such as those commonly found in Brother machines, this condition becomes noticeable very quickly, since control quality plays a decisive role.

Repair Process and Refurbishment

As part of the refurbishment, the servopack was completely overhauled. This included thorough cleaning, inspection of all relevant assemblies, and the preventive replacement of critical components that experience shows to be responsible for such fault patterns.
Particular attention was paid to the power section, the internal power supply, and the control and measurement circuits.

After completion of the repair, the servopack was tested on our test bench under realistic conditions. Both static and dynamic load cases were simulated. The Y axis could now be controlled smoothly, quietly, and reproducibly again, even under higher torque demands. The overload shutdown no longer occurred.

Test Result and Finalization

Following successful repair, the SGDH-20EEY338 showed stable control behavior across the entire operating range. The axis ran smoothly, responded precisely to setpoint changes, and remained within permissible operating limits even under load.
The servopack was then returned to the customer and now ensures reliable operation of the Brother CNC machining center.

Conclusion

This repair case clearly demonstrates that irregular motion and overload shutdowns are not necessarily caused by the motor or the mechanical system. Very often, the root cause lies within the servopack itself, particularly due to age-related changes in the internal control circuits.
A professional refurbishment of the Yaskawa SGDH-20EEY338 restores full functionality, extends the service life of the machine, and prevents costly downtime.

Further information such as price and delivery time for:
Yaskawa SGDH-20EEY338 Servopack

More details about our Yaskawa repair expertise can be found here: Yaskawa Brother SIGMA II repairs by Industrypart

Technical Specifications

Typical Applications

Compatible Motors and Systems

Functional Description

Alarms and Troubleshooting (Excerpt)

Main Assemblies

Service and Maintenance Notes