FANUC
FANUC Servo Amplifier Repair (A06B Alpha / Alpha i / Beta) — Mail-In
Component-level repair for FANUC servo amplifiers across the alpha, alpha i, and beta series (A06B-6079, -6096, -6114, -6117, -6130 and more). Free evaluation with a firm quote; typical repairs run $650–$1,500 versus $2,500+ for exchange units.
Coverage: Alpha (A06B-6079 / 6096) · Alpha i (A06B-6114 / 6117) · Beta i (A06B-6130 / 6132) · one to three axis
✓Fixed — or it's free
Unrepairable units are refunded; evaluations cost $0
✓24-month warranty
Every repair covered, parts and labor
✓3–5 business days bench time
Rush (1–2 day) and emergency service available
✓Program preserved
Your application and settings stay in the unit
Symptoms this repair fixes
- ✓Servo alarms: overcurrent, IPM fault, discharge alarms
- ✓Blown fuses / trips main breaker
- ✓Dead amplifier — no LEDs
- ✓Fault after a motor or cable short
- ✓Overheat trips from failed cooling fans
Honest limits
- ✕Faults that live in the motor, encoder, or cabling (our evaluation identifies this honestly before you spend anything)
What you get
- ▸Free bench evaluation and firm quote — no work without your approval
- ▸IGBT / IPM power-stage replacement with new components
- ▸Gate-driver, DC bus, and control power-supply repair
- ▸Current-sensor and encoder-interface repair
- ▸Full recap of aged electrolytics as standard practice
- ▸Powered bench verification appropriate to the module class
- ▸24-month warranty
Your program is safe
Servo amplifier parameters live in the CNC, not the amplifier — a repaired amp goes back in without reprogramming in nearly all cases.
Common part numbers we see
Part-number pages for this service
How FANUC Servo Amplifier units actually fail
Most units we receive fail in one of a handful of well-understood ways. Here is what each fault looks like from the machine, what is happening electronically, and what we do about it at the bench.
Power module failure
- What you see
- Overcurrent alarm, a drive that trips the instant it is enabled, or visible damage inside the unit.
- Why it happens
- The IGBT power stage fails short, usually because of a downstream fault — a shorted motor winding or a motor cable that has chafed through — rather than spontaneously. This is why the cable and motor must be checked before a repaired drive goes back on.
- What we do
- The power stage is tested device by device cold, failed devices replaced, gate drive verified, and the drive run under load before it ships.
DC bus capacitor degradation
- What you see
- Undervoltage or bus alarms, or a drive that runs but faults under hard acceleration.
- Why it happens
- Bus capacitors lose capacitance and gain ESR with years of service, so the bus can no longer hold up against the current demand of an accelerating axis even though it appears fine at idle.
- What we do
- Bus capacitors are assessed and replaced, then bus behaviour is verified under a real load rather than at rest.
Cooling and thermal alarms
- What you see
- Overheat alarms, often after the machine has been running for a while, sometimes clearing after a rest.
- Why it happens
- A seized fan or a heatsink packed with production dust. This is one of the most common reasons a drive is condemned, and one of the least expensive to put right.
- What we do
- Cooling is restored and thermal performance verified under load — and if this is genuinely all that was wrong, the evaluation will tell you so.
Feedback interface damage
- What you see
- Encoder or feedback alarms, erratic positioning, or an axis that will not hold position.
- Why it happens
- The feedback interface takes damage from cable faults and shorts pushed back into the drive, and can also degrade independently of the power stage.
- What we do
- Feedback circuitry is tested and repaired, then position and following behaviour verified on a running load.
Servo amplifier faults are frequently symptoms rather than causes. A drive that failed because a motor cable shorted will fail again within hours of being replaced if the cable is not found. That is why the evaluation reports what we found rather than simply confirming that the drive was faulty — and why the pre-shipment checks above genuinely matter.
What happens on the bench
The same sequence on every 6-stage repair, so nothing gets skipped because a fault looked obvious.
- 1
Safe intake and bus discharge
Drives arrive holding charge in the DC bus capacitors. The unit is discharged and verified at zero before anything is opened — this is a genuine hazard on any drive with a large capacitor bank, not a formality.
- 2
Power stage integrity check
The IGBT or power module is checked device by device for shorted and open junctions before power is ever applied. Energising a drive with a shorted power module simply destroys more of it, so this is done cold, first, every time.
- 3
DC bus and pre-charge inspection
Bus capacitors are assessed for capacitance loss and elevated ESR, and the soft-charge circuit — inrush resistor and its bypass relay or contactor — is checked. A drive that reports undervoltage or trips on power-up very often has a failed pre-charge path rather than a failed power stage.
- 4
Gate drive and feedback circuitry
Gate driver stages and their isolation are tested, because a partially degraded driver produces asymmetric switching that reads as an intermittent overcurrent fault under load and as a perfectly healthy drive at idle. Encoder and feedback interfaces are checked for the damage a shorted motor cable pushes back into the drive.
- 5
Thermal path and cooling
Fans, heatsink airflow and thermal interfaces are serviced. A large share of "failed" drives are thermal alarms caused by a seized fan or a heatsink packed with production dust.
- 6
Powered test under load
The repaired drive is brought up through a controlled power-on and run against a load so the power stage, current regulation and thermal behaviour are proven in operation — not merely confirmed to power up without alarming.
Check these before you ship
Some of these will tell you the unit is fine and the fault is elsewhere. We would rather you find that out now than pay to ship a good unit.
- □Megger the motor and its cable before condemning the drive. A shorted winding or a cable chafed against the machine frame will destroy a replacement drive exactly as fast as it destroyed the first one.
- □Record the alarm code and what the machine was doing when it tripped — during acceleration, at speed, on a hard stop, or only when warm. That distinction separates a power-stage fault from a thermal or feedback fault.
- □Check whether the cooling fan still spins freely and whether the heatsink is clogged. If the only fault is a thermal trip, cleaning and a fan may fix it on your bench.
- □Confirm incoming line voltage and phase balance. Repeated drive failures on one axis are often a supply or wiring problem the drive is simply reporting.
- □Note your parameter set if you have it recorded. Drive parameters normally live in the CNC or the drive's protected storage and our physical repairs do not touch them, but a record is worth having.
Repair or replace?
Servo and spindle drives are where repair economics are most favourable: the hardware is expensive, frequently obsolete, and often tied to a specific machine and parameter set. New replacements for older platforms are commonly quoted at multi-week lead times when they are available at all, and a like-for-like replacement still has to be parameterised and commissioned against the machine. Because a drive failure usually stops the machine outright, the number that matters is rarely the invoice — it is how many production days pass before the axis turns again.
What to ship
- ▸The amplifier module only — no motors or cables
- ▸The exact alarm number and what the machine was doing when it faulted
- ▸Machine make/model (helps us test against the right configuration)
Full packing guidance: mail-in instructions.
Ship your unit to
USPS
Control Board Lab
PO Box 120241
Arlington, TX 76012
UPS / FedEx
Control Board Lab
1009 Oakwood Ln # 120241
Arlington, TX 76012
Write your RMA number on the outside of the box and include it on a note inside. Units over 50 lb (large VFDs, spindle drives, industrial PCs in enclosures) ship by freight — contact us before ordering and we will arrange dock-to-dock shipping.
Frequently asked questions
What does a FANUC servo amplifier repair typically cost?
Most single-axis alpha/beta amplifier repairs land between $650 and $1,500 depending on the failure and module size — against $2,500+ for exchange units and far more for scarce models. The evaluation is free and the quote is firm before any work begins.
How do I know it's the amplifier and not the motor?
Tell us the alarm number — many FANUC alarms distinguish amplifier faults from feedback/motor faults. Our bench evaluation tests the amplifier independently, so if the fault is actually in your motor or cable we tell you, you pay nothing, and you've ruled out the expensive box.
Do you repair obsolete FANUC amps that FANUC no longer supports?
Yes — legacy Series 0 / 16 / 18 / 21-era amplifiers are a specialty. Third-party repair is often the only remaining service path for these, and donor components remain available.
Start with a free evaluation
Ship it in, get a firm quote, approve before any work — pay nothing if it can't be repaired.
The Fixed-or-Free Guarantee: if we can't repair it, you don't pay for the repair.
Call (817) 799-7332 · 📱 Text us a photo of your unit · Email repairs@controlboardlab.com