The MR-J2S-40B is Mitsubishi Electric’s 400 W MELSERVO-J2 Super series servo amplifier for 200 V single-phase or three-phase AC power supply with SSCNET optical fibre network interface — a legacy servo amplifier from Mitsubishi’s second-generation MELSERVO Super platform, providing 400 W continuous servo control at 3 A via original SSCNET communication for HC-KFS43 and HC-MFS43 series servo motors in active J2S SSCNET multi-axis systems managed by Q172CPU or Q173CPU motion controllers. The MR-J2S-40B is available through Atlantech Drives — quote within 24-48 hours, worldwide express shipping, 12-month warranty.
What Is the MR-J2S-40B?
The MR-J2S-40B is a MELSERVO-J2 Super series servo amplifier providing 400 W (0.4 kW) continuous output power via original SSCNET optical fibre — the 400 W model in the MR-J2S-B SSCNET sub-series, providing double the continuous power of the MR-J2S-20B for medium-load axis requirements in J2S SSCNET multi-axis systems. The MR-J2S-40B is compatible with Mitsubishi HC-KFS43, HC-MFS43, and equivalent 400 W servo motors with the J2S-era encoder, operated under the control of a Q172CPU or Q173CPU MELSEC-Q motion controller via the original SSCNET optical fibre chain. Like the MR-J2S-20B, the MR-J2S-40B uses the original SSCNET protocol — physically and electrically incompatible with SSCNET III (MR-J3-B) and SSCNET III/H (MR-J4-B) — making the MR-J2S-40B part of a fully integrated J2S legacy system where every component (controller, cables, amplifiers, motors) must be maintained at the same generation level. The maintenance replacement scenario for the MR-J2S-40B is therefore the same as for the MR-J2S-20B — a direct like-for-like replacement is required, and any platform upgrade requires simultaneous replacement of all system components. The MR-J2S-40B communicates with the legacy MR Configurator software via RS-232C for parameter access and servo tuning, and does not include a built-in STO safety function.
Key Technical Specifications
- Model: MR-J2S-40B
- Rated Output Power: 400 W (0.4 kW)
- Power Supply: 200–240 VAC single-phase or three-phase, 50/60 Hz
- Continuous Output Current: 3.0 A
- Maximum Output Current: 9.0 A (3× continuous peak)
- Compatible Servo Motors: HC-KFS43, HC-MFS43 (J2S-era motors only)
- Command Interface: SSCNET optical fibre (original SSCNET, not SSCNET III)
- Communication Cycle: 0.888 ms
- Encoder Interface: Serial encoder (J2S-era HC motor encoder protocol)
- Safety Function: None built-in
- Regenerative Brake: Built-in
- Communication: RS-232C (MR Configurator legacy software)
- Compatible Motion Controllers: Q172CPU, Q173CPU
- Operating Temperature: 0°C to 55°C
- Dimensions (W × H × D): 40 mm × 130 mm × 120 mm
- Weight: Approx. 0.8 kg
Typical Industrial Applications
The MR-J2S-40B is found in active service in multi-axis J2S SSCNET systems built during the MELSERVO-J2 Super platform’s active production period (approximately 1999–2008), where 400 W axes provide the correct balance of motor frame size, speed, and continuous torque for medium-load positioning tasks. In multi-axis assembly machines with Q172CPU or Q173CPU motion controllers, the MR-J2S-40B drives wrist axes, tool positioning axes, and product transfer axes where the axis load requires more than the 200 W MR-J2S-20B can provide but falls within the 400 W MR-J2S-40B continuous rating. Rotary indexing tables with 100–200 mm dial diameters, rotary tool changers in machining centres, and rotary axis drives in printing and labelling machines from the J2S era commonly use the MR-J2S-40B at the primary servo axis where 400 W provides adequate torque for the combined inertia and friction of the indexing mechanism. In J2S-era semiconductor and FPD (flat panel display) manufacturing equipment where multiple axes are coordinated by a Q172CPU or Q173CPU motion controller at 0.888 ms SSCNET cycle, the MR-J2S-40B drives medium-load precision positioning axes where 400 W provides the torque reserve needed for fast acceleration to the inter-step transit speed while maintaining adequate position settling accuracy. Medical device assembly machines and analytical instrument axes from the J2S era use the MR-J2S-40B for sample transport, measurement head positioning, and reagent dispensing axis drives where the combination of moderate axis mass, high cycle rate, and precision settling accuracy suits the 400 W J2S platform. Currently active MR-J2S-40B units requiring maintenance replacement are most commonly encountered in facilities with large equipment fleets from the early-to-mid 2000s — semiconductor manufacturers, electronics assembly operations, and precision instrument makers — where the equipment’s mechanical performance remains acceptable but individual servo amplifier failures require parts no longer available from standard distribution channels.
Replacement & Upgrade Notes
The MR-J2S-40B upgrade path to current technology involves the same constraints as all MR-J2S-B amplifiers: simultaneous replacement of the amplifier, servo motor, SSCNET cables, and motion controller is required — component-by-component migration within the original SSCNET system is not possible due to the SSCNET / SSCNET III / SSCNET III/H protocol incompatibility. The complete J2S SSCNET system upgrade path is: Q172CPU → Q172DSCPU or RD77MS (motion controller), original SSCNET cables → SSCNET III or SSCNET III/H POF cables, MR-J2S-40B → MR-J3-40B or MR-J4-40B (amplifier), HC-KFS43 → HG-KR43 or HG-MR43 (motor). This complete upgrade provides 22-bit encoder resolution, built-in STO safety function (MR-J4), AVSC II resonance suppression, and compatibility with the current MR Configurator2 commissioning tool and GX Works3 motion programming environment. For facilities where the J2S SSCNET system upgrade cannot be justified economically for all axes simultaneously, a partial approach is not possible — the entire chain must be migrated at once. The business case for MR-J2S-40B fleet migration should include the increasing cost and lead time for sourcing authentic replacement units, the risk of extended production downtime if a critical axis failure coincides with a period of poor aftermarket availability, and the productivity improvement from the higher servo bandwidth and improved auto-tuning of the J4 generation. Atlantech Drives maintains verified stock of MR-J2S-40B units for immediate dispatch — contact us for current stock levels and lead time confirmation before planning maintenance schedules that depend on MR-J2S-40B availability.
Frequently Asked Questions
Q: What is the difference between the MR-J2S-40B’s original SSCNET and the SSCNET III used by MR-J3-B amplifiers?
A: Original SSCNET (MR-J2S-B) operates at 5.6 Mbps using a specific optical wavelength and connector type, with a proprietary J2S-era communication protocol. SSCNET III (MR-J3-B) operates at 10 Mbps using a different optical wavelength and plastic optical fibre push-pull connector (identical physical connector to SSCNET III/H but different protocol). While both systems use optical fibre as the physical medium, the two are entirely incompatible — different wavelengths prevent optical signal coupling even if the connectors could be physically adapted. The practical consequence is that MR-J2S-40B amplifiers can only operate on original SSCNET chains managed by Q172CPU/Q173CPU controllers, not on SSCNET III chains managed by Q172DSCPU/Q173DSCPU controllers.
Q: Can an MR-J2S-40B from a decommissioned machine be reused in an operational MR-J2S SSCNET system?
A: Yes, provided the unit is in good condition and the servo parameters are correctly configured for the new application. Before installing a used MR-J2S-40B from a decommissioned machine, connect MR Configurator via RS-232C and read the current parameter set — compare the key parameters (motor code, encoder type, servo gains) against the requirements of the target machine. Write the target machine’s correct parameters to the replacement unit before servo-on, and perform auto-tuning with the actual mechanical load to establish correct servo gains for the new application. Also inspect the unit’s capacitors for bulging or leakage, and verify the cooling fan operates smoothly, before deploying a used unit in a production-critical application.
Q: Is the MR-J2S-40B physically compatible with the MR-J2S-20B in terms of panel mounting?
A: Yes. The MR-J2S-40B and MR-J2S-20B share the same 40 mm housing width and the same DIN rail mounting clip arrangement, enabling adjacent installation in multi-axis panels without panel modification when axes of different power ratings are installed side by side. Both models have the same overall housing height and depth, making the J2S-B sub-series layout dimensionally consistent across all models from 200 W to 700 W (which has a wider housing).
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