13.05.2026 by Viktor Siebert
Production Downtime Caused by Mitsubishi MDS-B-V14-35 Servo Drive Unit with Sporadic Alarm 32
Introduction as a Real Service Case.
A Mitsubishi MDS-B-V14-35 Servo Drive Unit arrived from a CNC production facility because the machine repeatedly stopped with intermittent Alarm 32. The fault did not occur continuously, but sporadically under load. This type of fault is especially critical in industrial production because the machine may restart after a reset, but the next downtime can occur at any moment.
According to the MDS-A/B-V1 alarm table, Alarm 32 is defined as PMOC, Power Module Overcurrent. The meaning: an overcurrent condition was detected in the IPM of the main circuit.
Initial Diagnosis
After arrival, the Mitsubishi MDS-B-V14-35 was first visually inspected. The installed assemblies were:
| Type | Designation on PCB | Quantity |
|---|
| Control board | RK112A-11 or BN634A980G51 | 1 |
| Power board | RK122D-V14-35 or BN638A019G51A | 1 |
| Power section | Power section | 1 |
The first inspection focused on:
| Inspection Step | Observation |
|---|
| Visual inspection | no safe release possible without detailed power section inspection |
| DC bus inspection | checked for abnormalities in the main power circuit |
| Power section | focus on IPM, gate drive circuitry and thermal interfaces |
| Connectors | checked for contact problems and aging |
| Circuit boards | inspection of control board and power board |
| Load condition | fault pattern matched sporadic overcurrent under operating conditions |
Actual Root Cause
The documented Alarm 32 directly points to Power Module Overcurrent. In the Mitsubishi MDS-D/DH alarm table, Alarm 32 is also listed as Power module error overcurrent, where the power module itself detects the overcurrent condition.
The repair process therefore focused on the following fault chains:
- sporadic overcurrent shutdown in the power section
- thermally stressed IPM or power semiconductor area
- possible aging of the RK122D-V14-35 / BN638A019G51A power board
- contact problems in the motor output or DC bus circuit
- load spikes originating from the machine
- conductive contamination and aged thermal interfaces
Repair Measures
The MDS-B-V14-35 was not simply reset but fully repaired. Especially with intermittent Alarm 32 conditions, a basic function test without load is insufficient.
The following work was performed:
| Measure | Purpose |
|---|
| Cleaning of assemblies | removal of conductive contamination |
| Power section inspection | evaluation of IPM and output current circuit |
| Power board inspection | verification of drive and signal paths |
| Control board inspection | exclusion of evaluation faults |
| Rework of thermally stressed areas | stabilization under temperature variation |
| Connector inspection | prevention of intermittent failures |
| Load testing | simulation of the customer fault condition |
Final Testing and Return Shipment
After the repair, the unit was tested on a dedicated test bench under defined operating conditions. The focus was placed on repeated startup cycles, load changes and thermal behavior. The Servo Drive Unit was only released for shipment after Alarm 32 could no longer be reproduced.
Customer Feedback
“The axis is now running stable again. Previously Alarm 32 occurred intermittently, but now we were able to return the machine to production.”
To mentioned Mitsubishi Drive: Mitsubishi Servo Drive Unit MDS-B-V14-35
More details about our Mitsubishi repair services can be found here:
Mitsubishi drive Repair by Industrypart
📞 Feel free to contact us with any questions about your Mitsubishi drive technology.
Our expert team is happy to help!
Technical Data
| Feature | Value |
|---|
| Manufacturer | Mitsubishi |
| Model | MDS-B-V14-35 |
| Device class | Servo Drive Unit / Servo Amplifier |
| Axes | 1 axis |
| Power | 3.5 kW |
| Series | MELDAS MDS-B |
| Typical CNC environment | M500 / M600 |
| Successor series | MDS-C1-V1-35 |
| Current | not specified in provided excerpts |
| Frequency | not specified in provided excerpts |
| Software version | not specified |
| Protection class | not specified |
Operating Conditions
| Condition | Value |
|---|
| Operating ambient temperature | 0 °C to +55 °C |
| Humidity | max. 90 % RH, non-condensing |
| Installation location | indoor use |
| Environment | free from oil mist, corrosive gases and direct sunlight |
| Altitude | up to 1000 m without derating |
Cooperation with Other Devices
| Category | Details |
|---|
| Motors | HA103, HA200 according to provided device data |
| Controllers | MELDAS CNC environment |
| Series | commonly M500 / M600 |
| Successor | MDS-C1-V1-35 |
| Interfaces | NC communication, motor power, detector/feedback, depending on machine configuration |
Functional Description
The Mitsubishi MDS-B-V14-35 operates as a single-axis CNC servo amplifier. It supplies the servo motor through the power section, processes CNC command values and monitors feedback, current, voltage and internal protection functions.
In the event of Alarm 32, the protection circuit intervenes because the power module detects an overcurrent condition. The drive stops to prevent consequential damage to the power section, motor or machine drivetrain.
Alarm and Error Codes
| Alarm | Fault Name | Meaning | Reset | Action |
|---|
| 17 | A/D converter error | current feedback error | PR | inspect drive |
| 31 | Overspeed | motor speed exceeded | PR | inspect feedback, parameters and load |
| 32 | Power module overcurrent | overcurrent in power module / IPM | PR | inspect motor cable, insulation and power section |
| 33 | Overvoltage | DC bus voltage too high | PR | inspect power supply and regeneration |
| 3A | Overcurrent | excessive motor current | PR | inspect motor, cables, load and control |
| 3B | Power module overheat | power module overheated | PR | inspect fan, cooling and environment |
| 3C | Regeneration circuit error | braking circuit fault | PR | inspect resistor and regeneration circuit |
| 45 | Fan stop | fan failure with overheating | PR | replace fan, clean heatsink |
| 46 | Motor overheat / Thermal error | motor or detector overheated | NR | inspect load and temperature |
| 50 | Overload 1 | motor or drive overloaded | NR | reduce load, inspect mechanics |
| 51 | Overload 2 | maximum current requested too long | NR | inspect mechanics, motor cable and parameters |
| 88 | Watchdog | drive not operating correctly | AR | inspect environment, disturbances and drive |