Servo drive repair

Output stages, DC bus, and encoder feedback

A servo drive is built from an input/rectifier section, a DC bus with bulk capacitors, an IGBT or MOSFET output stage, a control board, and the encoder-feedback circuitry that reads position and velocity back from the motor. The output stage is the most exposed part, since a shorted winding or a mechanical overload on the axis can take out the switching devices fast. DC-bus capacitors age on heat and time, the same as in any drive, and tend to fail quietly until the bus voltage sags or trips. Encoder-feedback inputs are the part most specific to a servo drive: a damaged feedback cable, a broken connector pin, or electrical noise on the feedback line can drop the loop entirely, and the drive faults rather than running blind.

The angle: OEM support that outlives the drive

Servo drives are paired tightly to the machine they run, to the axis, the motor, and the mechanical load, and that machine typically stays in service for decades, well past the catalogue life of the drive itself. When the manufacturer stops supporting a model, the options narrow fast: gamble on a used unit of unknown history and unknown remaining life, or fund a full retrofit of drive, motor, and control system to bring the axis current. Repairing the drive that’s already installed is the option in between.

Repair the original, keep the tuning

Repairing the installed drive keeps its existing tuning, gain and loop parameters, and its mechanical pairing to the motor intact, since none of that changes when a board is fixed rather than swapped. A retrofit doesn’t have that advantage: a new drive-and-motor combination has to be re-tuned to the axis from scratch, which is real commissioning time on a machine that was otherwise running fine before the failure.

Brands, scope, and the VFD distinction

Yaskawa, Fanuc, Mitsubishi, and Allen-Bradley servo drives and servo amplifiers come in for the same underlying faults. This page covers closed-loop servo drives and servo amplifiers with encoder feedback, the drives that hold an exact position or path on an axis rather than just a set speed. A variable-frequency drive (VFD) is a different device, typically running an AC induction motor open-loop with no encoder closing the loop back to the drive, and that’s a separate service; see VFD repair if that’s the closer match for what’s on the bench. This is independent repair; we are not an authorized or affiliated service center for any of the manufacturers named.

Free diagnosis, local or mail-in

Every servo drive is diagnosed free and quoted firm before any work starts. Mail-in is open nationwide, and local pickup and drop-off are available in Palm Bay and Melbourne, Brevard County.