Contactor,circuit breaker,sensor,Encoder,PLC,Converter
MR-J4: MELSERVO-J4 servo series
W2: 2-axis integrated drive (one unit controls 2 motors)
77: Rated power of each axis: 750W + 750W
B: SSCNETⅢ/H fiber bus interface for fiber synchronous control, compatible with Mitsubishi motion CPUs
📋 Main Specifications
| Item | Specification |
| Number of axes | 2 axes |
| Rated power per axis | 0.75kW (750W) |
| Power supply | 3-phase / single-phase AC200～240V, 50/60Hz (marked on label: 3PH+1PH 200-240V) |
| Communication bus | SSCNETⅢ/H (high-speed fiber synchronization) |
| Safety function | Built-in STO Safe Torque Off (compliant with IEC 61800-5-2) |
| Dynamic brake | Built-in |
| Dimensions | W85 × H168 × D195 mm |
| Weight | 2 kg |
| Encoder support | 22-bit absolute encoder (4,194,304 p/r) |
| Certifications | CE, UL/cUL, UKCA, RoHS |
| HS code | 85044095 |
🛠️ Compatible Motors
Compatible with Mitsubishi HG-MR73 / HG-KR73 (750W J4-series servo motors), supporting absolute encoders.
🎯 Typical Applications
Multi-axis synchronous equipment: chip mounters, inspection platforms, transfer modules, CNC auxiliary machines, packaging machinery, semiconductor equipment.
Advantage: Two axes share one drive, saving cabinet space and reducing cost.
🔄 Replacement Options
- Upgrade to new generation (J5)：MR-J5W2-77B (same 2-axis rating, SSCNETⅢ/H compatible, improved performance)
- Separate drive solution：2 pcs MR-J4-70B (single-axis 750W, larger footprint)
- Legacy replacement：Predecessor MR-J3W-77B. Wiring and program differences, not plug-and-play
This is a bus-type servo drive; pulse command control is not supported directly. It must be used with Mitsubishi motion controllers (Q/R series motion CPU) via SSCNET fiber link.
USB port for commissioning; configured with MR Configurator2 software.
Spare parts: Power board, CPU board, CNP connector with individual part numbers (303772, 303769, etc.)
MR-J4W2 (MR-J4W2-77B) Alarm / Fault Code List
Description: MR-J4W2 2-axis integrated type B (SSCNETⅢ/H). Alarms are divided into fault alarms (latched, reset required) and warnings (no shutdown, prompt only).
Suffix .1/.2 stands for Axis 1 / Axis 2, which is critical for this 2-axis model.
Readout: Drive panel or MR Configurator2 software; alarm history can be saved with waveform data for troubleshooting.
- Fault Alarms (ALM, machine shutdown)
Alarm Code Name Brief Cause & Troubleshooting 10 Undervoltage Insufficient DC bus voltage; missing phase, voltage drop, poor contact of contactor, damaged rectifier module 12 Memory error Internal ROM / flash failure; replace drive if fault persists after power cycle 13 Clock error Internal RTC failure; drive replacement is generally required 15 Power circuit error Pre-charge / soft-start circuit failure on main power side 16 Ground fault Short to earth of motor power cable, motor winding insulation breakdown 19 Main circuit error IPM or power driver hardware damage 1A Motor combination error Mismatched motor model in PA01/PA02; wrong encoder cable or motor selection (.1 Axis1, .2 Axis2) 20 Encoder initial communication error Handshake failure at power-up; broken encoder cable, loose connector, faulty encoder 24 Encoder communication error Communication dropout during operation; EMI interference, poor shield on long cable, water ingress in connector 25 Encoder Z-phase error Abnormal encoder zero signal 2B Encoder counting error Count disorder caused by interference or encoder hardware failure (.1 Axis1, .2 Axis2) 30 Regeneration error Broken regenerative resistor, wrong resistance value, excessive regenerative power; built-in regeneration insufficient, external resistor required 31 Overspeed Motor speed exceeds limit; abnormal command, encoder feedback fault, runaway due to excessive gain 32 Overcurrent Hardware / software overcurrent; phase-to-phase short circuit in motor, shorted power wire, IPM breakdown, mechanical jam 33 Overvoltage DC bus over-limit; excessive energy feedback during deceleration, high input voltage, failed regeneration circuit 34 SSCNET receive error 1 SSCNETⅢ/H fiber communication fault: bent fiber, contaminated end face, loose connector, faulty fiber port on motion CPU 35 Command frequency error Illegal command sent from upper motion controller 36 SSCNET receive error 2 Fiber synchronization timing error, multi-axis link synchronization fault 37 Parameter error Parameter out of range or checksum error; restore factory settings and re-download parameters 3A Surge suppression circuit error Soft-start circuit failure at power-on 3E Operation mode error Mismatch between control mode parameter and SSCNET configuration on master side 42 Full-closed control error External linear scale feedback fault (only for full-closed loop mode) 45 Main device overheat Power module overheat; blocked cooling air duct, fan stall, high ambient temperature 46 Motor overheat Motor thermal sensor triggered; continuous overload, poor motor heat dissipation (.1 Axis1, .2 Axis2) 47 Cooling fan fault Drive internal fan stall / low speed; foreign object jamming, fan aging 50 Overload 1 Continuous overload (electronic thermal protection); mechanical binding, high friction, undersized selection 51 Overload 2 Peak overload; impact load, sudden mechanical lock 52 Position excessive error Position deviation exceeds threshold; lost pulses, mechanical jam, low gain, excessive command speed (.1 Axis1, .2 Axis2) 54 Vibration detection Servo oscillation; excessive gain, mechanical resonance 56 Forced stop alarm STO safety circuit open, emergency stop triggered, disconnected STO wiring 61 Operation error Illegal command while servo ON, sequence control error 63 STO timing error Timing mismatch between two STO channels, asymmetric safety wiring 64 Safety setting error Incorrect STO safety parameter configuration Warnings (WARN, servo keeps running, alert only)
| Warning Code | Name | Description |
| 91 | Drive overheat pre-warning | Temperature approaching protection threshold |
| 92 | Battery cable break | Absolute encoder battery wire disconnected; dead battery, loose plug |
| 95 | STO warning | Single STO channel abnormal (single wire open, shutdown alarm not triggered yet) |
| 96 | Home setting warning | Faulty home signal logic or home proximity signal |
| 9B | Position deviation pre-warning | Position error close to alarm threshold |
| 9F | Battery low warning | Encoder battery voltage low; replace battery soon to avoid home position loss |
| E0 | Regeneration overload warning | Sustained high regenerative load |
| E1 | Overload warning 1 | Load approaching overload threshold |
| E2 | Motor overheat warning | Motor temperature rising |
| E3 | Absolute counter warning | Abnormality of absolute position counter |
| E4 | Parameter warning | Unreasonable parameter setting (no latch-up) |
| E6 | Drive-side forced stop warning | STO / E-stop triggered at drive side |
| E7 | Controller forced stop warning | Stop command issued by upper motion CPU |
| E8 | Fan speed drop warning | Fan aging with reduced speed, not stalled |
| E9 | Main circuit OFF warning | Main power cut off while control power remains energized |
| EB | Other axis alarm (2-axis specific) | The other axis on this drive has an active fault |
| EC | Overload warning 2 | High peak load detected |
| ED | Output power limit warning | Continuous output power close to rated limit |
| F0 | Tough drive instantaneous power dip warning | Tough drive function activated by voltage fluctuation |
| F2 | Drive log write error | Internal fault recorder access failure |
| F3 | Vibration diagnostic warning | High mechanical vibration detected by diagnostic function |
Special Notes for MR-J4W2 2-Axis Drive
- Suffix .1 = CH1 (Axis 1)；.2 = CH2 (Axis 2). Confirm faulty axis first; motor and encoder of the two axes are independent.
- EB warning is unique to this multi-axis model: When one axis faults, the other axis reports EB to indicate the companion axis failure. Do not troubleshoot EB directly; check the real alarm code on the other channel.
- 34 / 36 fiber alarms: For SSCNETⅢ/H fiber, clean end face first, minimum bend radius ≥30mm, avoid sharp bends.
- STO (56, 63, 95): Two STO channels must switch synchronously; inconsistent timing triggers code 63.
- Alarm reset: Remove root cause first, turn servo SON OFF then reset. Some hardware faults cannot be cleared by power cycling.
Mitsubishi MELSERVO Servo Drive Model List
General suffix definition
A: Pulse + analog interface (pulse command type)
B: SSCNETⅢ/H fiber bus (fiber synchronization with motion CPU, MR-J4W2-77B belongs to this type)
GF / G: CC-Link IE / CC-Link IE TSN Ethernet bus
W2: 2-axis integrated; W3: 3-axis integrated
D1/D2/D3: Separate power type (amplifier unit paired with MR-CV power supply)
Numeric code for power rating (10=0.1kW, 20=0.2kW, 40=0.4kW, 60=0.6kW, 70=0.75kW, 100=1kW, 200=2kW, 350=3.5kW, 500=5kW, 700=7kW)
RJ: Special specification version
Active Series (Available for new orders)
- MR-J5 Series (Latest generation, MELSERVO-J5, 3.5kHz response)
Single-axis
MR-J5-10A / 20A / 40A / 60A / 70A / 100A / 200A / 350A / 500A / 700A 【Pulse type】
MR-J5-10G / 20G / 40G / 70G / 100G / 200G / 350G / 500G / 700G 【CC-Link IE TSN】
MR-J5-10B / 20B / 40B / 70B / 100B / 200B / 350B 【SSCNETⅢ/H fiber】
Multi-axis integrated
MR-J5W2-22B / 44B / 77B / 1010B / 2020B (2-axis, SSCNET fiber)
MR-J5W3-222B / 444B / 777B (3-axis, SSCNET fiber)
MR-J5W2-22G / 44G / 77G / 1010G (2-axis, CC-Link IE TSN)
MR-J5W3-222G / 444G / 777G (3-axis, CC-Link IE TSN)
Separate power type (Common DC bus regeneration system)
MR-J5D1-G4-N1 (1-axis), MR-J5D2-G4-N1 (2-axis), MR-J5D3-G4-N1 (3-axis)
Matching power unit: MR-CV4 regenerative converter
- MR-J4 Series (Mature mainstream, your model belongs here)
Single-axis
MR-J4-10A / 20A / 40A / 60A / 70A / 100A / 200A / 350A / 500A / 700A / 11KA / 15KA / 22KA
MR-J4-10B / 20B / 40B / 60B / 70B / 100B / 200B / 350B / 500B / 700B (SSCNETⅢ/H)
MR-J4-10GF / 20GF / 40GF / 70GF / 100GF (CC-Link IE Field)
Multi-axis integrated (Focus: MR-J4W2 / J4W3)
MR-J4W2-22B (0.2+0.2kW)
MR-J4W2-44B (0.4+0.4kW)
MR-J4W2-77B (0.75+0.75kW, your model)
MR-J4W2-1010B (1+1kW)
MR-J4W2-2020B (2+2kW)
MR-J4W3-222B / 444B / 777B (3-axis integrated)
MR-J4W2-0303B6 (Low-power special version)
Separate amplifier unit
MR-J4-DU900B / DU11KB / DU15KB / DU22KB, used with MR-CV regenerative power supply
- MR-JE Economy Series (Low-cost, pulse / simple bus, low power range)
MR-JE-10A / 20A / 40A / 70A / 100A / 200A
MR-JE-10C / 20C / 40C / 70C (EtherCAT version, JE-C)
Application: Simple feeding and transfer; SSCNET fiber multi-axis synchronization is not supported
- MR-JN Micro Economy Series (Ultra compact, 10~100W)
MR-JN-10A / 20A / 40A / 60A / 100A
Application: Small rotary tables, miniature slides, entry-level low-power
⏸️ Obsolete Series (Spare parts market only, not recommended for new machines)
MR-J3 (Production discontinued, stock spares reducing)
Single-axis: MR-J3-10A /20A/40A/70A/100A/200A/350A / MR-J3-10B/20B/40B/70B
Multi-axis: MR-J3W-22B / MR-J3W-44B / MR-J3W-77B (J3 2-axis, predecessor of J4W2)
CC-Link version: MR-J3-10T / 20T /40T
MR-J2S (Legacy, manufacturer repair service terminated)
MR-J2S-10A/20A/40A/70A/100A/200A/350A, MR-J2S-10B, MR-J2S-CP (built-in positioning type)
MR-J2 (Erly first generation, nearly phased out)
MR-J2-10A、MR-J2-20A, etc.
📌 Auxiliary Units (Common servo system accessories)
MR-CV: Regenerative power converter (common DC bus system for J4/J5D)
MR-RB: External regenerative braking resistor
MR-TB: Terminal block adapter
📎 Quick Selection Reference for MR-J4W2-77B
Same-series replacement: MR-J4W2-77B
Upgrade to new generation: MR-J5W2-77B (SSCNET compatible, preferred direct upgrade)
Separate drive alternative: 2 pcs MR-J4-70B
Economy alternative: JE series does not support SSCNET fiber, cannot replace directly
