Beckhoff AX5000 Servo Drive Repair and EtherCAT Commissioning
Several Beckhoff AX5000 digital compact servo drives came into the workshop dead on the control supply: apply 24 V DC and the front display stayed dark. Units in this batch included a AX5118-0000-0202 (18 A rated) model and earlier AX5112 / related AX51xx hardware from the same plant.
The work had two parts: component-level repair of a common power-path fault, then workshop commissioning on EtherCAT against a Beckhoff PLC in TwinCAT so the drives could be returned knowing fieldbus and state-machine behaviour were intact.
AX5112 digital compact servo drive on the bench — EtherCAT X04/X05, 24 V control and power terminals.
Fault on the 24 V path
With only the external 24 V control supply connected, a healthy AX51xx wakes the display and control electronics. These units drew little or no useful current, or failed to complete start-up.
Opening the drives pointed at the same area seen on previous AX5000 repairs: a pair of Schottky rectifiers on the secondary of the high-frequency supply that feeds the low-voltage control circuitry. On multiple units those diodes measured short-circuit. Replacing them with Diodes Incorporated B560C / B560CQ-13-F (60 V, 5 A, DO-214AB) restored boot up on the affected units.
Control-board detail — B560C Schottky pair in the 24 V supply path that repeatedly failed short.
Not every unit was only diodes. One AX5118 had an open PCB fuse on the 24 V path (confirmed by comparison with a sister unit); after the fuse was restored the display came up and reported the expected DC-link undervoltage with no mains applied. Others showed destructive damage and were not returned as working drives.
Heat / arc marking at a board–heatsink interface on a failed AX51xx power/control assembly.
Charred AX5140-related control board — isolator area destroyed; this class of damage is beyond a diode swap.
EtherCAT commissioning on a Beckhoff PLC
After hardware repair, each drive was connected to a Beckhoff PLC over EtherCAT and brought up in TwinCAT:
PLC in Config mode; remove stale devices; Scan for EtherCAT devices
Confirm the AX51xx appears on the bus
Online view of the drive — DLL / port status (Port A = front IN, Port B = front OUT)
Step the EtherCAT state machine: INIT → BOOT → Pre-Op → Safe-Op
With control power only (no 415 V mains / DC link), Safe-Op correctly raised an undervoltage / DC-link fault. That is the expected workshop result: communications and state machine proven without spinning a motor.
Five repaired drives were exercised this way so the machine builder could reinstall knowing EtherCAT and the CoE/SoE state machine responded before on-machine motor tests.
A dark AX5000 display on 24 V is often not a “dead CPU.” On this series it has repeatedly been the Schottky pair on the control supply secondary — a short, a fuse, or both — followed by a structured TwinCAT EtherCAT prove-out so the drive is not returned blind. Where the board is burned or the power stage is destroyed, the honest outcome is strip for parts rather than a false repair.