Initial situation and fault description.

The Mitsubishi MDS-C1-V2-1005 Servo Drive Unit was sent to us with a fault that was initially difficult to pinpoint. According to the customer, the alarm Al. 32 (Power Module Overcurrent) appeared only very rarely at first. The machine sometimes operated for several days without any issues before the alarm occurred again unexpectedly. Over time, the situation worsened: what began as an occasional fault developed into an almost daily problem.

The most critical aspect for the customer was the impact on production. Each occurrence of the alarm required a complete machine restart, including re-referencing and full setup. This resulted in significant downtime, tied up personnel and led to increasing frustration in daily operation. Eventually, it became clear that continuing operation under these conditions was no longer acceptable.

Although a replacement unit from the manufacturer was theoretically available, it was not a viable option for the customer. Besides the very high costs, another factor played a decisive role: the customer learned that these units are no longer repaired by the manufacturer but are simply disposed of when replaced. For a company that consciously operates in a sustainable manner, this was a major argument against replacement. Through recommendations within their network, the customer finally contacted us.

Initial inspection and diagnosis in the workshop

After receiving the unit, a standardized incoming inspection was carried out. Externally, the drive showed no obvious damage. There were no visible burn marks and no mechanical defects. In practice, these cases are often the most challenging, as the root cause is not immediately apparent.

The MDS-C1-V2-1005 was then prepared for testing on our internal test bench. The objective was to reproduce the fault under controlled conditions. Especially with Alarm 32, this step is essential, as the fault is often temperature- or load-dependent and does not necessarily occur immediately.

During extended test runs under load, unstable behavior of the power stage became apparent. The current draw was no longer symmetrical, and thermal irregularities in the power module could be measured. This confirmed that the issue was not caused by external factors but by internal aging and pre-damage of the unit.

Repair strategy and preventive approach

For this type of fault, we deliberately avoid a simple “remove-the-fault” repair. Replacing only the obviously defective components would have carried a high risk of a repeat failure. Instead, a preventive repair strategy was applied.

The power assembly was completely inspected. Age-related weaknesses in the current path and control circuitry were specifically addressed. In addition, thermally stressed components were replaced as a preventive measure. Particular attention was paid to the cooling system, as insufficient heat dissipation is a common root cause of power module failures, even if the alarm itself appears much later.

At the same time, the control board was inspected, cleaned and electrically tested. The goal was to ensure that no secondary damage or unstable reference signals were present that could further stress the power section.

Test setup and long-term testing

After completion of the repair, the drive was once again operated on the test bench. A structured test procedure was used. The servo drive ran for several hours under varying load conditions. Temperature development, current characteristics and protective functions were continuously monitored.

Especially with faults that previously occurred sporadically, a short functional test is not sufficient. Only long-term testing provides real confidence. During the entire test period, Alarm Al. 32 did not reoccur. Current consumption remained stable, and thermal values stayed well within permissible limits.

Quality assurance through checklists

An essential part of our work is the use of internal checklists. For this unit, all steps were documented: incoming condition, diagnosis, repair actions, test parameters and final release. This structured approach ensures that no step is overlooked and that the repair process remains fully traceable and reproducible.

For the customer, this means maximum transparency, high operational reliability and a significantly extended service life of the device.

To mentioned Mitsubishi Drive: Mitsubishi Servo Drive Unit MDS-C1-V2-1005

More details about our Mitsubishi repair services can be found here:
Mitsubishi drive Repair by Industrypart

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Mitsubishi MDS-C1-V2-1005

Technical specifications

Main assemblies

Relevant alarms (excerpt)

Conclusion

The Mitsubishi MDS-C1-V2-1005 clearly demonstrates how a fault that initially appears harmless and sporadic can develop into a serious production risk. Through a consistent preventive repair approach, a structured test setup and clear checklists, the unit was restored in a sustainable manner. For the customer, this means not only significant cost savings compared to replacement, but also a clear commitment to responsible and sustainable handling of industrial electronics.