CNC Controller Repair
CNC control board and controller repair for all major systems — Fanuc, Siemens 840D, Mitsubishi, Heidenhain, NUM, Fagor and more.
Your CNC machine is your most valuable production asset — every hour of downtime costs lakhs in lost output. We get it back online fast.
CNC machine downtime is extremely costly — a single day of unplanned stoppage can mean lakhs in lost production. Synchronics maintains one of the largest CNC controller repair capabilities in India with specialist teams for Fanuc, Siemens Sinumerik 840D/810D/828D, Mitsubishi M80/M70/M700, and Heidenhain TNC systems. We repair main CPU boards, axis control cards, spindle drive cards, I/O modules, display units, and MDI keyboards at the component level, backed by axis simulation testing on our in-house test benches before dispatch.
Diagnosis Guide
Common CNC Controller Problems We Fix
Experiencing any of these symptoms? Our engineers have diagnosed and repaired thousands of these faults.
Main CPU Board Failure
Controller does not boot, blank screen, watchdog alarm, or stuck at boot logo
Electrolytic capacitor ageing, power surge damage to voltage regulators, or corrupted firmware EPROM
Axis Control Card Fault
SV alarm (Fanuc) or 700xxx alarm (Siemens), axis runaway, following error, or intermittent position drift
DAC output drift, encoder interface IC failure, optical fibre transceiver degradation, or feedback cable noise
Spindle Drive Card Blown
SP alarm, spindle does not rotate, overcurrent trip during orientation, or speed fluctuation
Gate driver IC failure, power MOSFET/IGBT short from motor insulation breakdown, or current sensor fault
I/O Module Error
IO alarm, specific input/output not responding, intermittent signal dropout, or fieldbus communication error
Optocoupler degradation from relay kickback, blown fuse on output channel, or corroded connector pins
Display / Keyboard Malfunction
Dim or flickering display, blank screen, unresponsive keys, or ghost key presses on MDI panel
Backlight inverter capacitor failure, LCD ribbon cable oxidation, or membrane keypad wear
Battery Backup Loss (Program Loss)
Low battery alarm, all stored programs and parameters lost after power cycle, machine requires re-homing
Lithium battery depleted beyond safe voltage, SRAM chip failure, or battery holder contact corrosion
How It Works
Our CNC Controller Repair Process
A systematic, schematic-driven repair process — from receipt to dispatch.
Receive & Log
Controller received, photographed, and logged with machine details, fault history, and alarm codes reported by the customer.
Program Backup Attempt
Before any board-level work, we attempt to back up stored CNC programs, tool offset tables, and machine parameters via serial or memory card.
Main Board Diagnosis
Systematic board-level diagnosis — power rails measured, clock signals verified, bus communication probed, and processor boot sequence analysed with oscilloscope and logic analyser.
Axis & Spindle Card Test
Axis control cards tested on our servo test bench with actual servo motors. Spindle cards tested with spindle motor load for speed control, orientation, and C-axis operation.
Component-Level Repair
Faulty ICs, capacitors, MOSFETs, and connectors replaced with original-spec or equivalent components. BGA rework station used for fine-pitch IC replacement.
Simulation Test & Dispatch
Repaired controller run on our CNC simulation bench — full axis movement, spindle operation, I/O test, and communication check before dispatch.
Thorough Inspection
CNC Controller Inspection Checklist
Every unit goes through a comprehensive inspection checklist before and after repair.
Main CPU Board
Axis Control Cards
Spindle Drive Card
I/O Modules
Display Unit
Battery Backup & Memory
The Synchronics Advantage
Why Choose Us for CNC Controller Repair
Fanuc & Siemens CNC Expertise
Our CNC team has repaired over 5,000 controllers across Fanuc 0i to 30i series, Siemens 840D/810D/828D, and Mitsubishi M80/M70. We maintain a reference library of known-good waveforms and schematics for rapid diagnosis.
Program Preservation Guarantee
We understand that CNC programs represent years of machining expertise. Our program backup protocol is executed before any repair work begins — your programs, tool tables, and parameters are preserved and returned with the repaired controller.
Axis Simulation Testing
Every repaired axis card and spindle card is tested on our in-house CNC test bench with actual servo and spindle motors — not just bench-tested with a multimeter. We verify full closed-loop operation before dispatch.
Troubleshooting
Common CNC Controller Fault Codes We Repair
Seeing one of these error codes? We diagnose and repair the root cause.
Fanuc Servo Alarm — VRDY OFF / DRDY OFF
Axis card not receiving ready signal from servo amplifier — check amplifier power, emergency stop chain, or axis card relay driver
Fanuc Spindle Alarm — Spindle motor overheat / overcurrent
Spindle motor insulation breakdown, current sensor drift on spindle drive card, or blocked cooling fan
Fanuc Overtravel — Stored stroke limit 1 exceeded
Encoder feedback fault causing position drift, axis card DAC offset, or corrupted machine parameters
Fanuc System Alarm — ROM parity / RAM parity error
EPROM data corruption, SRAM chip failure, or low battery causing data loss during power-off
Siemens Sinumerik Axis Alarm — Drive fault
SINAMICS drive module fault, motor cable issue, encoder signal loss, or axis card communication error on DRIVE-CLiQ
Siemens NCK Alarm — NCU internal error
NCU main board hardware fault, CompactFlash card corruption, or NCK software crash requiring firmware reload
These are representative fault codes. We handle all Fanuc i-series alarms, Siemens Sinumerik 840D/828D alarms, Mitsubishi M80/M70 alarms, Heidenhain errors, and other CNC controller error codes. Send us your alarm screenshot for a free diagnosis estimate.
Industries Served
Where CNC Controllers Are Used
CNC Machining Centres
VMC and HMC controller repair — 3-axis, 4-axis, and 5-axis machine controllers, ATC control boards, and pallet changer logic
CNC Turning Centres
Lathe and turn-mill controller repair — C-axis spindle cards, live tool turret control, and sub-spindle synchronisation boards
CNC Milling & Boring
Floor boring machine and gantry mill controllers — large-axis servo cards, high-torque spindle drive repair, and linear scale interfaces
EDM Machines
Wire-cut and die-sink EDM controller repair — spark gap control boards, wire feed servo cards, and dielectric system controllers
Laser Cutting Machines
Fibre and CO2 laser cutting controller repair — motion control cards, laser power control boards, and height sensing modules
Injection Moulding
CNC-controlled IMM controller repair — hydraulic proportional valve cards, barrel temperature controllers, and sequence logic boards
Trusted Brands
Brands We Service
Component-level repair for all major manufacturers
FAQ
Frequently Asked Questions
Absolutely. Program preservation is our top priority. Before any board-level work begins, we execute a full backup of your stored programs, tool offset tables, work coordinates, and machine parameters using RS-232, memory card, or CompactFlash — depending on the controller model. The backup is returned to you along with the repaired controller.
Yes. We repair the complete range of Fanuc CNC controllers — from the older Fanuc 6/10/15 series through the Fanuc 16i/18i/21i series to the latest Fanuc 30i/31i/32i systems. Our team handles servo alarms (SV), spindle alarms (SP), overtravel alarms (OT), system alarms (PS), and power module faults across all series.
Yes. We carry out NCU main board repair and can reflash or replace the CompactFlash card with the correct Sinumerik software version. We also repair the associated SINAMICS drive modules, Active Line Modules, and Motor Modules that form part of the Siemens 840D sl system.
We maintain a dedicated CNC test bench equipped with Fanuc and Siemens servo motors, encoders, and spindle motors. Every repaired axis card is run in closed-loop operation — we verify position accuracy, following error, velocity loop response, and current loop performance before dispatch. This is far more reliable than simple power-on bench testing.
Yes, we provide CRT-to-LCD retrofit solutions for older Fanuc, Siemens, and Heidenhain systems where original CRT monitors are no longer available. The retrofit includes a compatible LCD panel, signal converter board, and mounting bracket designed to fit the original CNC cabinet cutout.
India's Leading CNC Controller Repair Service
Synchronics Electronics Pvt. Ltd. is one of India's most trusted CNC controller repair companies, operating from a state-of-the-art facility in Vadodara, Gujarat. With over 15 years of experience and more than 5,000 CNC controllers repaired, we serve precision machining shops, automotive component manufacturers, aerospace suppliers, die-mould makers, and OEMs across India. Our repair capability spans the full range of Fanuc, Siemens Sinumerik, Mitsubishi, Heidenhain, Fagor, NUM, Mazak, Haas, and Okuma CNC systems.
What sets us apart is our investment in CNC-specific test infrastructure. We do not simply bench-test repaired boards with a multimeter — we run every repaired axis card and spindle card on actual servo and spindle motors in closed-loop operation, verifying position accuracy, velocity response, and current control before the controller leaves our facility. Combined with our program preservation guarantee and a 6-month warranty on every repair, Synchronics delivers the confidence that your CNC machine will be back in production — running right — the first time.
Get Your Equipment
Back in Action — Fast
Send us your faulty industrial electronics. Our engineers will diagnose it and provide a detailed quote within 24 hours — with no obligation to proceed.
Free Evaluation
No obligation
48hr Turnaround
Fastest in India
6-Month Warranty
Every repair
No Fix, No Charge
Zero risk policy
Pan-India Pickup
Doorstep service