Alarm A.41 although the Servopack switches on

The display is on, but the axis remains stopped. A Yaskawa SGDH-20DE-OY may report undervoltage even though the unit can be switched on. An active control circuit and a functioning power supply are separate matters. This workshop example documents a confirmed internal fault and its repair.

Function and unit identification

The SGDH-20DE-OY is a Yaskawa Sigma-II SERVOPACK. Together with a suitable servo motor, it forms a drive system. Replacement selection requires the complete model designation, execution and existing parameters. A similar model name alone does not establish compatibility.

Model, version and voltage class are visible in the outgoing photographs. The power rating comes from the product data. Installation must follow the full nameplate and documentation applicable to the actual unit.

What does A.41 mean?

For this power class, A.41 indicates low DC-bus voltage. It identifies a condition rather than a unique failed component. The supply and internal charging circuit are relevant investigation areas. Resetting an alarm does not resolve its cause.

Practical fault investigation

Safely stop the machine before any work. Inspection and repair require qualified personnel. The machine, motor, cables and Servopack form one system. Include information about the circumstances of the fault even when only the amplifier is sent for repair.

Workshop example: charging circuit repaired

The inspected SGDH-20DE-OY could be powered on during the incoming inspection. The customer parameters were backed up. Its history contained repeated A.41 entries and other historical messages. Inspection confirmed a charging-circuit fault as the cause of A.41. The history does not prove that all recorded alarms were active simultaneously.

We dismantled and thoroughly cleaned the unit, repaired the affected circuit and carried out an overhaul following the checklist. The customer parameters were then restored, and the alarm history was cleared after the work was completed.

Test result and its scope

The final functional test of the Servopack was successful. The unit was documented as cleaned, repaired, overhauled and tested. The customer motor supplied with it was explicitly not included in this final test. The result therefore does not establish the condition of the complete drive system in the customer machine.

Prevention and information for a service enquiry

A readable nameplate, exact alarm, occurrence timing and saved alarm history help us assess an enquiry. Back up customer parameters before changes. Avoid unnecessarily frequent switching of the main power supply. After reinstallation, check the axis under its actual operating conditions.

Sources

https://files.omron.eu/downloads/latest/manual/en/sigma-ii_users_manual_en.pdf
Yaskawa Sigma-II user manual, alarm overview and troubleshooting in chapter 10. Workshop information is based on the documented inspection and repair of the photographed unit.

Workshop video

The explanation combines the confirmed findings with original functional-test footage. The customer motor supplied with the drive was not included in that test.

Unit photographs

Enquiry and matching product

Need support with a Yaskawa SGDH-20DE-OY? Send us the complete designation, version and a fault description. We can assess repair, overhaul or a suitable replacement.
https://www.industrypart.com/products/yaskawa-sgdh-20de-oy-servopack-5998.html

Additional Sigma-II alarms

This series-manual overview is for orientation. It is not a list of confirmed faults on the inspected unit. Options and execution may affect which messages apply.

Diagnosis depends on the message, its timing and actual machine conditions. In this workshop case, the charging-circuit fault was confirmed. This does not establish an additional encoder defect.