FANUC
FANUC Spindle Amplifier / Drive Repair (A06B-6078 / 6088 / 6111 / 6121) — Mail-In
Component-level repair for FANUC spindle amplifiers (SPM series: A06B-6078, -6088, -6111, -6121 and related). Free evaluation, firm quote before work, typical repairs $750–$1,800.
Coverage: Alpha SPM (A06B-6078 / 6088) · Alpha i SPM (A06B-6111) · Beta i (A06B-6121) and related
✓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
- ✓Spindle alarms (AL-01, AL-02, AL-12 class faults)
- ✓Dead spindle drive
- ✓Trips on acceleration or under load
- ✓Blown input stage after a phase event
Honest limits
- ✕Failures in the spindle motor itself or magnetic sensor (identified honestly at evaluation)
What you get
- ▸Free bench evaluation and firm quote
- ▸IGBT / power-stage replacement
- ▸Gate-driver, bus, and control-supply repair
- ▸Fan replacement and thermal verification
- ▸Full recap as standard
- ▸24-month warranty
Your program is safe
Drive parameters live in the CNC — reinstalling a repaired spindle amp rarely requires reprogramming.
Common part numbers we see
Part-number pages for this service
How FANUC Spindle 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 stage failure
- What you see
- Overcurrent alarms, tripping on spindle acceleration, or a drive that faults as soon as it is enabled.
- Why it happens
- Spindle drives handle high current during acceleration and braking, and the power devices fail under that duty — often precipitated by a motor or cable fault downstream.
- What we do
- Power devices are tested cold and replaced, gate drive verified, and the amplifier proven under load.
DC bus capacitor wear
- What you see
- Bus or undervoltage alarms, or faults that appear only during hard spindle acceleration.
- Why it happens
- Spindle duty is hard on the bus capacitor bank because of the current demanded during ramps. Aged capacitors cannot support those transients even when the drive is fine at steady speed.
- What we do
- The capacitor bank is assessed and replaced, and behaviour verified under load through acceleration rather than at rest.
Cooling failure and thermal trips
- What you see
- Overheat alarms after a period of running, sometimes clearing once the machine has stood.
- Why it happens
- Failed cooling fans and heatsinks clogged with swarf and dust, which is routine in a machining environment.
- What we do
- Cooling is restored and thermal behaviour verified while the amplifier is running under load.
Spindle feedback faults
- What you see
- Speed or orientation alarms, spindle failing to orient, or unstable speed control.
- Why it happens
- Damage or degradation in the spindle feedback interface, sometimes originating in a sensor or cable fault at the machine.
- What we do
- Feedback circuitry is tested and repaired, and stable speed control confirmed under load.
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 spindle amplifier module only
- ▸Alarm number + machine make/model
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
The machine shows a spindle alarm only under load — worth sending the amp?
Load-dependent trips are commonly failing power stages or aged bus capacitors inside the amplifier — both repairable. Send the alarm number with the unit; if evaluation shows the amp is healthy, you pay nothing and can chase the motor side with confidence.
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