This month's product spotlight falls on the Mitsubishi MDS-A-SP and MDS-B-SP unit is offered in sizes starting at 0.4kW and leads up to 55kW. It also has a few features which make it easy and effective to use within a system. An easy to read display allows for quick alarm reading for troubleshooting as well as easy monitoring for each unit. The converter, which was conventionally built within the spindle, is now located within the power supply unit. This allows the spindle unit to be smaller in size and also much lighter than previous versions.

Through the use of a high-speed CPU, speed response is improved and allows for quicker maneuverability. Additionally, spindle parameters can all be loaded from the NC side allowing enhanced operability.

Common Failures – Alarm Codes and Troubleshooting Steps:


When it comes to Mitsubishi MDS-A-SP and MDS-B-SP spindle drives, there are quite a few different alarms that can occur and be displayed on the 7-segment display. Although there are many potential alarm codes, there are a few that seem to occur more often than others.

One of the most common alarms on this type of unit is A.32 which refers to an overcurrent flow detected through the power module. One of the first checks that can be done once this alarm occurs is disconnecting the motor leads (U, V, W) from the drive and check each output phase of the drive to ground for any short in the circuit. If this passes and there is no short between ground and each leg, it can then be attempted to run with the motor disconnected and verify if the A.32 alarm still occurs or if a different alarm comes up. In many cases, if the A.32 reoccurs after disconnecting the motor leads, there is an internal fault that usually requires further evaluation and repair. When this alarm occurs, regardless of the previously mentioned test results, it is always recommended to meg the motor using a megohmmeter which checks the insulation as well as checking the resistance between each phase combination. More details on this can be found here and in the video below.

In addition to A.32, another frequently seen alarm is A.37. This distinguishes an initial parameter error and in most cases can be viewed on the control screen, which will designate a parameter number with the alarm code. This designated parameter can be checked in the control unit and verified to be properly set. If this is not set properly at the time, setting this to the correct value and then power cycling the machine can help alleviate this alarm from the drive. If the parameter is properly set and the unit is not able to be reset to pass that A.37, it has commonly been found that board level components within the unit are faulty and further evaluation or repair is required.

A full list of alarms and error codes can be found here, but please note that certain codes pertain to different units. This is designated by the SV, SP, and CV columns found in the document. For any further assistance with Mitsubishi MDS-A-SP and MDS-B-SP spindle units, please contact us at or by phone at 800.551.4420.