Robot & FANUC Power Supply Repair Services
Signs of a failing power supply
A failing power supply rarely announces itself cleanly. Maintenance teams usually see a controller that will not power up, an amplifier that trips as soon as the robot moves, or a CNC that drops out mid-cycle. On FANUC systems the PSM (Power Supply Module) reports specific alarm codes: code 3 for an abnormal heat-sink temperature rise, code 4 for a DC-link voltage drop, code 5 when the main-circuit capacitor fails to recharge in time, code 6 for decreased control power voltage, code 7 for abnormally high DC-link voltage, and code A when the external cooling-fin fan has stopped. On R-30iB controllers, a red ALM LED on the power-supply unit signals a power-supply alarm, and the +24V circuit is protected by fuse F4. Welding power-supply alarms ARC-143 and ARC-144 point to communication faults between control boards and CPUs, while ASBN-191 indicates a power-supply control-memory error. None of these alarms confirm the module itself is bad — a shorted load, bad cable, blown fuse, or downstream board can trigger the same code.
How the repair works
Repair starts with a visual inspection for burned components, physical damage, contamination, bulging capacitors, and overheated connectors. From there we work the input path first — fuses, bridge rectifiers, input capacitors, and switching devices — before extended powered testing, since this is where most catastrophic failures originate. Common repair candidates include electrolytic capacitors, rectifiers, diodes, MOSFETs, IGBTs, switching controllers, driver ICs, fuses, relays, cooling fans, and damaged solder joints or traces. Capacitor degradation is a frequent root cause: it increases ripple, impairs DC-link charging, and produces intermittent startup or undervoltage symptoms long before a hard failure. A failed fan or restricted airflow raises heat-sink temperature and accelerates failure of the switching devices, capacitors, and control electronics around it. On FANUC controller power supplies we also inspect connectors, harnesses, fuses, grounding, and the boards fed by each DC rail, since a downstream fault can present as a power-supply alarm. Before any unit is substituted, we verify the exact part number, revision, input voltage, output rating, and connected load.
Models and part families we repair:
- FANUC Alpha and Alpha-i PSM (Power Supply Module) units from CNC amplifier systems
- FANUC R-30iA and R-30iB controller power-supply assemblies
- FANUC 0i, 16i, 18i, and 30i CNC power-supply and Alpha/Alpha-i drive-related assemblies
- Yaskawa Motoman robot controller power supplies
- ABB robot controller power supplies
- KUKA robot controller power supplies
Testing and verification before return
Before a repaired unit leaves the bench it is verified under load, not just powered up with nothing connected. We measure output voltage, regulation, current delivery, ripple, and noise using an electronic load or equivalent load equipment to confirm behavior as demand changes and at full load. Where the unit’s design allows safe verification, we exercise protection functions — overvoltage, overcurrent, short-circuit, and the related shutdown and recovery behavior — to confirm the supply responds correctly rather than failing open. Every repaired unit then runs through a controlled burn-in period so that components reaching normal operating temperature can expose a thermally intermittent fault that a cold power-up would miss. Diagnosis and verification use oscilloscopes, multimeters, electronic loads, power-supply testers, and LCR or component meters as appropriate to the fault. For FANUC robot-controller power supplies, verification also considers backplane connections, teach-pendant indications, and the connected robot or I/O hardware, since a supply can test correctly on the bench and still fault once reconnected to its original load.
Preventing power supply failures
Most power-supply failures trace back to preventable conditions rather than random component death. Dust and conductive contamination, blocked filters, high ambient temperature, vibration, poor cabinet ventilation, and loose power connections all shorten the life of capacitors, fans, and switching devices. A basic preventive maintenance routine covers cabinet cleaning, fan and filter inspection, terminal-torque checks performed under an approved safety procedure, thermal inspection of the cabinet and power-supply enclosure, and a review of recurring alarms rather than resetting them and moving on. Trending is worth the effort: periodic checks of DC output ripple and rail voltage can flag a deteriorating capacitor or a regulation problem weeks before it causes a shutdown. Watch for early warning signs such as a fan that runs louder or slower than normal, a cabinet that runs hotter than it used to, alarms that clear on reset but keep coming back, and any drift in output voltage or ripple measured during routine PM checks.
Repair versus replacement
A power-supply failure on a production robot or CNC is downtime measured in cycles and orders, not just an alarm on a screen. Repair or exchange is often faster and less disruptive than sourcing a new unit, particularly on older FANUC CNC and robot-controller generations where OEM replacement assemblies are discontinued, revision-dependent, and thin in stock. When a correctly rated OEM replacement is not available, component-level repair or an exchange unit can keep an otherwise sound, obsolete controller installation running — provided compatibility is confirmed from the complete part number and system configuration, not just the model family. A repair quotation should make clear whether the work is component-level refurbishment, an exchange-unit replacement, or a full controller replacement, since the cost and lead time differ for each path. Lead time itself depends on diagnosis findings, parts availability, the burn-in period required, and whether an exchange unit is on hand; it is not something that can be promised from an alarm code alone.
Why choose robotics integration
Robotics Integration works on FANUC power supplies first — PSM modules, R-30iA and R-30iB controller power supplies, and 0i/16i/18i/30i CNC power-supply and drive assemblies — along with power supplies for Yaskawa Motoman, ABB, and KUKA robot controllers. Support runs both ways: units can be shipped in for repair-and-return, or the diagnosis can happen on-site when the fault involves the controller backplane, wiring, or connected robot and I/O hardware rather than a standalone board. Quoting starts with identifying the exact unit — part number, revision, controller or CNC model, and the alarm or symptom involved — because a FANUC PSM alarm can originate in the module, a downstream board, a fuse, or a cable, and the repair scope depends on which one it is. From there the quote separates diagnosis from repair so a maintenance manager knows the cost of finding the fault before committing to the repair itself.
Get a repair quote
To get a quote on a FANUC power supply, PSM module, controller power-supply unit, or a Yaskawa, ABB, or KUKA controller power supply, send the following:
- Make and model of the robot or CNC controller
- Complete part number and revision of the power supply or PSM module
- Alarm code or fault description, including whether it is intermittent or immediate
- Input voltage and any conditions present when the failure occurred
- Photographs of the unit, connectors, and any visibly damaged boards
Call 1-602-449-1556 to discuss the fault or arrange a repair.
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