MITSUBISHI MDS-B servo troubleshooting

Common on-site troubleshooting cases

Case 1: Alarm 63 after power on (abnormal auxiliary regeneration)

Phenomenon: MDS-B-CV-110 alarms 63 when powered on and cannot be reset.

troubleshoot

Measure the resistance between L+and L -, which should be in the megaohm range. If it is low resistance, the regenerative transistor will break down

Check if the external regeneration resistor is short circuited or has a low resistance value

Solution: Replace the power unit or regenerative transistor module. Note that the regeneration circuit design of MDS-B-CV-370 is different and cannot be mixed.

Case 2: Restarting after emergency stop displays "6F" and cannot be moved

Phenomenon: After resetting the external emergency stop button, the NC has cleared the emergency stop state, but the driver still displays "q6F" and the axis cannot be enabled.

troubleshoot

Confirm whether the rotary switch SW1 of MDS-B-CV is set to 4 or 5 (enabling external emergency stop function)

Check if parameter PTYP has been added with 0040

Measure whether the 24V on the CN23 connector has been restored

Solution: If the external emergency stop circuit has been closed but still reports an error, it may be due to poor contact of CN23 or incorrect parameter writing. Reset PTYP and power off to restart.

Case 3: The vertical axis slides too far after power failure

Phenomenon: After emergency stop or power outage, the Z-axis slides down beyond the safe distance.

troubleshoot

Check if the delay time of the electromagnetic brake matches the parameters SV055/SV056

Confirm if the dynamic brake is effective (V1-110/150 requires an external DBU)

Solution: Set SV056 to the same value as the acceleration and deceleration time of CNC G0 (usually 40-200ms), and ensure that the brake power supply is delayed and cut off after the servo is turned off.

Maintenance and spare parts recommendations

Electrolytic capacitors: It is recommended to replace the electrolytic capacitors in the power unit and drive unit every 5 years under normal conditions to prevent aging and increase in ripple

Cooling fan: It is recommended to install an auxiliary fan (FAN2) in the distribution cabinet to maintain heat dissipation even if the unit's built-in fan (FAN1) fails

Battery: The battery unit for absolute position detection (MDS-A-BT-2/4/6/8) must be replaced while maintaining control power after the battery low voltage alarm, otherwise the absolute position will be lost

Firmware version: Differences in MDS-A series and B series servo software versions may result in parameter incompatibility. When replacing the drive unit, confirm that the software version is ≥ B0 (for serial pulse encoders)