Mitsubishi Electric · MR-J4 series
MR-J4-40A Repair
Mitsubishi MR-J4-40A servo amplifier (400W). The classic failure is a blown IPM (alarm AL.32 class) — a bounded, well-understood repair with deep parts supply. Free evaluation, firm quote.
Known failures on the MR-J4-40A
- ▸AL.32 overcurrent (blown IPM)
- ▸AL.10 / AL.30 faults
- ▸Dead amplifier
- ▸Breaker trip at power-on
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.
Check these before you ship
Some of these will tell you the MR-J4-40A is fine and the fault is elsewhere — worth ten minutes before you pay to ship it.
- □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.
Not your exact model?
Search the catalog or send us the number on your unit's label — we service far more than the catalog shows.
Why a MR-J4-40A fails — and what we do about it
The MR-J4 series shares its electronics across the family, so these are the faults we see on this part number again and again.
Power module failure
- What you see
- Overcurrent alarms, or a drive that trips immediately when enabled.
- Why it happens
- The power stage fails short, typically as a consequence of a shorted motor winding or a damaged motor cable rather than on its own. The downstream fault must be found or the repaired drive will fail again.
- What we do
- Power devices are tested cold and replaced, gate drive circuitry verified, and the drive proven under load.
Bus capacitor degradation
- What you see
- Undervoltage alarms, or faults appearing only under acceleration.
- Why it happens
- Capacitance loss and rising ESR after years in service leave the bus unable to support acceleration current.
- What we do
- Bus capacitors are assessed and replaced and behaviour verified under a real load.
Repair or replace a MR-J4-40A?
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.
Full technical detail for this repair
The Mitsubishi Servo Amplifier service page covers the complete bench sequence — how the unit is tested, what gets replaced and how it is proven before it ships back — along with the rest of the family we service.
Mitsubishi Servo Amplifier Repair — full details →Frequently asked questions
Can the MR-J4-40A be repaired?
Yes — al.32 overcurrent (blown ipm), al.10 / al.30 faults, dead amplifier are the failures we commonly repair on the MR-J4 series platform. It starts with a free bench evaluation and a firm quote you approve before any work — $0 if unrepairable.
How long does a MR-J4-40A repair take?
Standard bench time is 3–5 business days once the unit arrives. Rush service (+$149) moves it to 1–2 business days, and emergency same/next-day attempts are available — contact us first.
How do I send it in?
Start the repair online to get an RMA number instantly, pack the unit well with the RMA on the box, and ship it to our Dallas–Fort Worth lab with any carrier. Full packing guidance is on the mail-in instructions page.
Machine down? Let's get it back up.
Start a repair online in two minutes, or send us the part number for a free technician review.
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