Yaskawa SGDB-30ADGY8: Braking-circuit fault found during incoming inspection

A servopack can power up and still be unfit for operation. On this Yaskawa SGDB-30ADGY8, our workshop identified a short circuit in the braking circuit and a defective braking transistor. A loose screw that did not belong to the unit also fell out when the enclosure was opened. A connection between these findings was suspected, but not established as a proven cause. This report distinguishes the documented findings from the repair work and the final test.

Customer report and scope of work

The recorded instruction was a complete overhaul with cleaning and electrolytic capacitor replacement. The fault-description field does not contain a specific symptom from machine operation or an alarm code reported by the customer. The electrical findings below therefore originate from our incoming inspection. The customer approved the repair following the quotation.

Technical data of the documented servopack

These specifications were read from the nameplate of the submitted unit. The complete model designation, including GY8, must be retained when identifying the device.

Servo amplifier, motor and braking circuit

The servo amplifier supplies the motor and processes its feedback. During deceleration, energy can return to the drive. The electrical braking circuit examined here belongs to the servopack. A fault in this circuit does not automatically mean that a mechanical motor holding brake is defective. A meaningful test requires the correct combination of drive, motor, feedback and test settings.

Findings and completed repair work

The initial visual and mechanical inspection found no obvious external problem and no indication of a previous repair. When the main supply was switched on, the LED described as white in the workshop record remained illuminated. A short circuit was found between terminals “−” and “B”. The braking transistor within the transistor module was identified as defective. A motor test was initially not possible in this condition.

The loose screw was a separate physical finding. Its role in causing the short circuit remained a hypothesis. A replacement transistor module was requested, but its installation is not separately confirmed in the repair notes. We therefore do not present an undocumented module replacement as a completed action.

Troubleshooting and alarm reference

The measured braking-circuit fault must be distinguished from stored alarm history. Entries A.30, A.C2 and A.99 were recorded. This does not establish that all were active at once, nor does it prove that an encoder defect was present in this repair case.

The brief reference below is based on Yaskawa manual TSE-S800-16E for the SGDB series. Any machine-specific documentation for the SGDB-30ADGY8 variant must also be considered.

Final test and preventive measures

Following repair, the servopack was tested with a motor. The motor code was adjusted for the test setup. The motor then ran correctly, and the braking function was also recorded as satisfactory. The final motor test in both directions passed. Customer parameters were subsequently restored and the stored alarms cleared. The workshop completed the job as repaired, overhauled and tested.

This conclusion describes the documented workshop test. It does not establish a later production run at the customer’s site, a defined load test or additional numerical measurements. Keeping cooling paths clear, checking fans regularly and preventing loose foreign objects from entering the enclosure are useful preventive measures. Work inside an open servopack requires qualified personnel and compliance with the manufacturer’s isolation instructions.

Sources and scope

The case is based on the incoming inspection, repair and completion notes, the original nameplate, original photographs and the workshop test recording. Customer information and internal documents are not published.

Yaskawa: SGDB / Σ-Series User’s Manual, TSE-S800-16E, printed pages 507 (A.30), 521 (A.C2) and 528 (A.99). The series-level alarm reference does not replace verification of the particular machine configuration.

Workshop test video after overhaul

Original workshop footage with an explanation of the documented work.

Photos before, during and after repair

The after-repair photos show the original device with an edited grey background.

Repair enquiry for Yaskawa SGDB-30ADGY8

For assistance with a Yaskawa SGDB-30ADGY8, please provide the complete model designation, a clear nameplate photograph and a detailed description of the behaviour. Alarm indications and the conditions under which they occur help us prepare the inspection.

Yaskawa SGDB-30ADGY8 Servopack in our shop – repair, exchange and purchase. Availability and scope are confirmed for each enquiry.