Replacement CNC Parts Guide - Power Supplies, Circuit Board & More.
Keeping Your CNC Machines Running.
When a CNC machine goes down, the fastest fix is usually a tested replacement part, not a new machine. Most unplanned downtime traces back to a short list of electronic components: power supplies, circuit boards, drives and motors.
This guide covers what each part does, the signs it is failing, and what to check before you order a replacement for FANUC, Mitsubishi, Haas, Okuma and other CNC equipment. If you already know the part number you need, you can talk to an expert for a quote.
CNC Tools LLC replacement parts inventory.
Replacement Power Supplies. (Mitsubishi & FANUC)
A power supply converts incoming AC power into the stable DC voltages your control, I/O and drives depend on. When it fails, the whole machine usually stops, not just one axis.
On FANUC drive systems, the power supply module (PSM) feeds the DC bus shared by the servo and spindle amplifiers. On Mitsubishi MDS drive systems, the power supply (converter) unit plays the same role. Separate control power supplies run the CNC control, I/O units and operator interface.
Industrial CNC power supplies from FANUC, Mitsubishi, Haas, and Siemens, supporting reliable machine operation and industrial automation.
Common signs a power supply is failing:
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A power supply alarm on the control or on the module's status display
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The control resets on its own, or will not boot
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Several axes alarm at the same time, which points to a shared supply rather than a single drive
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Blown fuses, a burnt smell, or swollen capacitors
Before you order a replacement:
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Match the full part number from the label, including any suffix or revision letters
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Confirm whether you need a drive power supply or a control power supply
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Check the input voltage your machine is wired for
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Photograph the unit and its connections before removing it
Keeping one tested spare on the shelf is cheap insurance for shops that run several machines from the same brand.
Browse replacement power supplies.
Replacement Circuit Boards (Mitsubishi, Haas & Okuma)
Circuit boards handle the logic and communication inside a CNC: reading inputs, sending motion commands to the drives, and driving the operator display. A failed board often shows up as an alarm or behavior that seems unrelated to the board itself.
FANUC CNC Circuit Boards – Industrial Electronic Components
Boards we see replaced most often:
- Mitsubishi: boards for Meldas and M-series controls and MDS drive interfaces, covering axis control, I/O and communication
- Haas: I/O boards, motion control boards, and video and keyboard boards on vertical machining centers and lathes
- Okuma: boards for OSP controls, covering servo communication, spindle control, I/O and diagnostics
Common signs of a failing board:
- I/O or communication alarms that come and go
- A blank or flickering display, or keys that stop responding
- Faults that change with machine temperature or vibration
- An axis or spindle that will not respond even though its drive shows no alarm
Before you swap a board:
- Back up parameters, programs and offsets first
- Match the part number and revision exactly
- Check software or firmware compatibility with your control version, especially on Haas and Okuma machines
- Handle the board with ESD protection
Browse replacement circuit boards.
Other Replacement CNC Parts: Drives, Motors, Rotary Tables & Operator Controls.
Beyond power supplies and boards, these are the parts most likely to stop a machine. Each one is available for FANUC, Mitsubishi, Haas, Siemens and other major platforms.
| Part | What It Does | Signs It Needs Replacing |
|---|---|---|
| Servo drive | Turns control commands into precise X, Y and Z axis motion | Overcurrent or overload alarms, an axis that will not move or loses position |
| Spindle drive | Controls spindle motor speed and torque | Spindle alarms, spindle will not reach commanded speed, poor surface finish |
| CNC motor | Converts electrical power into axis or spindle movement | Grinding noise, overheating, encoder alarms |
| Rotary table | Adds a 4th or 5th axis for multi-sided machining | Indexing errors, backlash, unstable rotation |
| Teach pendant | Lets operators program and jog robots and automated cells at the machine | Dead buttons, damaged display, enable switch faults |
| Keyboard panel | The operator's main input for commands and adjustments | Keys that stick or stop responding, cracked membrane |
A drive alarm does not always mean the drive is bad. The motor, its cable or the power supply can trigger the same alarm, so check those before ordering.
How to Choose a Replacement Parts Supplier
The wrong part costs more than the price difference: another day of downtime, a return, and sometimes damage to other components. Before you buy, check that the supplier can answer yes to these:
- Is the part tested before it ships? Ask what the test covers, not just whether it was "checked."
- Can they confirm the exact match? Part number, revision and compatibility with your control version.
- Is it in stock and ready to ship? Lead time matters as much as price when a machine is down.
- Will a technician answer your questions? Before and after the sale.
- Can they repair your failed unit? Sometimes repair is faster or cheaper than replacement.
At CNC Tools LLC, every part we sell is tested on a test bench and on a machine that simulates real operating conditions before it ships, and our free technical support team helps you confirm the right part before you order. We also repair CNC electronics and buy back surplus parts, so spares you no longer need don't just sit on the shelf.
Bench testing comes first: our technicians check each board’s components and voltages before it moves on to a machine test.
Frequently Asked Questions
Can I use a part with a different revision letter? Sometimes. Many revisions are drop-in compatible, but some change connectors, firmware or settings. Send us the full part number and we will confirm before you order.
Should I buy new, surplus or refurbished? New parts for older machines are often discontinued or carry long lead times. Tested surplus and refurbished parts get you running faster at a lower cost, as long as they match your part number and are verified before shipping.
Do I need to back up anything before replacing a board or power supply? Yes. Back up parameters, programs and offsets before you swap any control board, and write down switch and jumper settings on the old unit.
What if I don't know which part failed? Send us the alarm codes, the machine model and photos of the part labels. Our technical support team can help narrow it down at no cost.
Get the Right Replacement Part, Fast
Whether you need a power supply for a FANUC drive system, a Haas I/O board or a servo drive for an older Mitsubishi machine, our team can help you find the right part and get it shipped. Send us your part number or alarm code and we will confirm compatibility and send a quote.
Contact our team today—we'll help you find the right solution for your equipment
📞 +1 (956) 246-7411