MachineryFix

Problems We Solve · Drives & Motion

Servo drive throwing an alarm?

Likely causes, what our technicians check onsite, and how to get it fixed — verified engineers across India, onsite in hours (under 4 in Hyderabad), 24/7.

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01 / Overview

Servo Drive Alarm

Servo alarms split cleanly into two groups, and knowing which you have saves a lot of money: feedback-side faults (encoder/resolver, cable, absolute-encoder battery) and power-side faults (amplifier overcurrent, overload, DC-bus). Replacing the amplifier for what is actually a broken encoder cable is one of the commonest wasted repairs we see.

We diagnose Siemens SINAMICS S120, Mitsubishi MELSERVO, Allen-Bradley Kinetix, Yaskawa Sigma, Delta ASDA and FANUC alpha-i/beta-i servo systems — isolating feedback from power before quoting, and recovering absolute-encoder data so referencing survives the repair.

02 / Diagnosis

Likely causes

The handful of things that actually cause this — in the order we rule them out.

DX_01

Encoder / feedback fault

A damaged encoder cable, a failed encoder/resolver, or noise on the feedback line. Alarms like Siemens F31xxx, MELSERVO AL.16, Yaskawa A.8xx or FANUC pulse-coder alarms point here.

DX_02

Absolute-encoder battery

A flat encoder-backup battery loses absolute position — the axis alarms on power-up and the machine needs re-homing. We restore or re-establish the position data properly.

DX_03

Amplifier overcurrent

A shorted output stage, a faulty motor winding or a mechanical jam draws overcurrent (MELSERVO AL.32, Sigma A.C10, PowerFlex/Kinetix overcurrent). We meter the amplifier and motor separately.

DX_04

Overload / following error

A binding mechanism, wrong gains or an under-sized axis causes overload (AL.50) or excessive following error. Sometimes it's the machine, not the drive.

DX_05

DC-bus / STO fault

Bus overvoltage from a braking-resistor problem, or a safe-torque-off circuit fault, will alarm the amplifier without any motor fault at all.

03 / Onsite

What our technician checks

A methodical path to root cause — not a scattergun of part swaps.

  1. 01Read the exact alarm code and its detailed diagnostic
  2. 02Separate feedback-side from power-side by testing the encoder and cable
  3. 03Megger the servo motor windings and check for mechanical binding
  4. 04Check absolute-encoder battery and recover position data
  5. 05Verify gains, brake circuit and DC-bus before condemning the amplifier

04 / Fix it

Related services

The services that resolve this fault.

Servo Drive RepairMotion Control & Servo TuningMitsubishi Servo RepairFANUC Servo Repair

05 / Questions

Frequently asked questions

How do I know if it's the servo drive or the motor/encoder?+
The alarm code tells us a lot: feedback alarms (encoder/cable) are a different family from power alarms (overcurrent/overload). We confirm by testing the encoder and cable independently and meggering the motor, so we replace the part that's actually faulty — often a cable, not the amplifier.
We got an absolute-encoder / battery alarm and lost our home position. Is that recoverable?+
Yes. We restore the absolute position where backup data exists, or re-establish homing and referencing properly where it doesn't, and fit a fresh encoder battery so it doesn't recur. The machine comes back correctly referenced.

Written & reviewed by MachineryFix Engineering Team — last reviewed — questions? Call +91 70751 47888

Servo Drive Alarm? Get a technician onsite.

Describe the fault and we'll match a verified specialist near you — onsite in hours across India, under 4 in Hyderabad. 24/7.

Book a TechnicianCall +91 70751 47888