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Expert Services

Expert Servo Drive Repairing

Precision feedback alignment and high-power IGBT inverter stage restoration.

Service Overview

Servo drives are critical for precise motion control in CNC machines, robotics, and high-speed packaging lines. Unlike standard VFDs, servo drives rely on complex feedback loops from encoders or resolvers. If the feedback circuit is faulty, or the power output stage is damaged, the system trips immediately. Our lab specializes in complete servo drive diagnostics, utilizing motor simulator setups to test and calibrate feedback signals alongside rebuilding power stages.

Supported Hardware Series & Models:

Yaskawa (Sigma-5, Sigma-7, Sigma-V)

Fanuc (Alpha and Beta Series)

Siemens (Sinamics S120, Simodrive)

Mitsubishi (Melservo J2S, J3, J4)

Delta (ASDA Series)

ABB (MicroFlex)

Panasonic (Minas A5/A6)

Common Failure Modes & Diagnostic Codes

Technical Reference Sheet for Engineers

Code / Symptom	Probable Cause	Engineering Remedy
Overcurrent / Ground Fault (OC/GF)	Short circuit in the IGBT inverter module, shorted output cables, or current sensor failure	Conduct static diode test on IGBTs. Replace shorted IGBT modules and current transducer ICs on the driver board.
Encoder / Resolver Feedback Error	Damaged line receiver optocouplers, encoder circuit component failure, or cable noise	Test the 5V encoder supply rail, replace differential line receivers, and realign encoder feedback timing.
Undervoltage / DC Link Fault	Soft-charge relay contact wear, failed rectifier diodes, or aged filter capacitors	Check soft-start resistor, replace bypass contactor/relay, and replace large DC link capacitor bank.
Gate Driver Fault	Blown gate resistors, failed optocouplers, or DC-to-DC converter failures	Replace high-speed gate drive optocouplers (e.g. HCPL-3120) and rebuild the isolated gate power supply rails.

Our Premium 6-Step Component-Level Repair Process

How we restore electronic components to manufacturer specifications

Incoming Visual & Thermal Inspection

Every unit is registered and subjected to high-definition visual inspection and thermal scanning. We identify blown trace lines, scorched resistors, swollen capacitors, and signs of liquid ingress before applying any power.

In-Circuit Analog Signature Analysis

Using advanced Tracker/Signature Analyzers (such as Huntron Trackers), we test passive components (resistors, diodes, capacitors, inductors) and active ICs while in-circuit. This safe, power-off testing compares component electrical signatures against known-good standards.

Semiconductor Power-Stage Diagnostics

For VFDs and servo drives, we test the high-power rectifier and IGBT inverter stages. We check the gate-drive circuit paths, desaturation protections, and replace gate optocouplers to prevent catastrophic future failures.

Microscopic Solder & SMT Reflow

Using ISO-certified temperature-controlled desoldering stations, our IPC-trained technicians replace damaged components. We execute precision micro-soldering under stereo-zoom microscopes for multi-layer PCBs.

Controlled Bench & Load testing

After repair, units are powered on via variable-voltage current-limiting power supplies. We run full closed-loop tests under real load conditions—testing communication links, analog/digital feedback loops, and thermal efficiency.

Final QC Certification & Protective Coating

The repaired PCB is cleaned in an ultrasonic chemical bath to remove flux residues. We apply a high-grade conformal coating to protect against moisture, dust, and corrosive industrial oils before releasing the unit with our warranty.

ISO 9001:2015 Certified

Why Choose Usha Engineering?

26+ Years of B2B Expertise

Established in 2000, we possess over a quarter-century of hands-on industrial electronic repair experience. We are an ISO 9001:2015 Quality Management System certified company.

Up to 70% Cost Savings

Repairing high-end industrial controllers and drives with Usha Engineering is significantly more cost-effective than purchasing expensive new OEM replacement units, which also require configuration.

Advanced Component-Level Lab

Our Panchkula HQ facility features state-of-the-art diagnostic equipment including logical analyzers, digital oscilloscopes, curve tracers, thermal imagers, and dedicated load test benches.

Pan-India Logistics & Quick Turnaround

We accept units shipped via secure courier from anywhere in India, offering express 48-hour turnarounds for critical breakdowns to minimize factory downtime.

Industries We Serve

Steel & Metallurgy

VFDs and PLCs controlling blast furnace loaders, rolling mills, heavy crane lifts, and cooling fans.

Textile & Spinning Mills

High-speed servo drives, HMI panels, and control cards on spinning frames, carding machines, and weaving looms.

Paper & Packaging

Multi-drive tension control systems, synchronous motors, and PLC controllers on web presses and slitting lines.

Pharmaceutical & Chemical

HMIs, PCBs, and control modules in pill press machines, packaging lanes, centrifuge drives, and mixing vessels.

CNC & Automotive Machining

Precision spindle drives, servo controllers, and logic units in 3-axis and 5-axis CNC machining centers.

Warranty Protection

3-Month Service Warranty

We stand behind our work. All board-level repairs performed by Usha Engineering Services are covered by a comprehensive 6-month warranty on replaced components and workmanship. We use only original, high-grade semiconductor parts sourced from certified global distributors.

Need Help Immediately?

Submit a diagnostics ticket or speak directly with an engineer to get a free estimate and arrange unit pickup.

Frequently Asked Questions

Clear answers regarding repair procedures, pricing, and warranties

How do you test servo drives without the matching motor?

We maintain a library of common industrial servo motors (Yaskawa, Fanuc, Siemens, Mitsubishi) in our lab. We plug repaired drives into matching test motors to verify closed-loop operation.

Can you repair feedback encoder interfaces?

Yes, we troubleshoot and repair encoder interface boards on the drive. We can repair optical and magnetic encoder reader circuits, line drivers, and connectors.

What is the typical cost of a servo drive repair?

Repairs typically cost 20% to 35% of the price of a new drive, representing significant savings, especially for obsolete CNC hardware.

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