28.07.2025 by Viktor Siebert
Repair Case: Mitsubishi MR-J2S-350B-S041U703 Not Everything “Refurbished” on eBay Works as Promised AC Servo Drive
A customer contacted us with a supposedly “refurbished-tested” unit bought on eBay from a Chinese seller. It was advertised as guaranteed functional and was meant to replace a failed original. However, the unit caused unstable behavior and frequent alarms in the machine.
Upon inspection, it became clear: The model label was manipulated. The suffix S041U703 refers to a custom hardware/software configuration, but neither the hardware nor the software in the device matched this. It was a standard version, retrofitted with a fake label to appear customized.
The customer was informed of the fraud, and we declined to proceed with repairs on the unit. Instead, he opted to have his original broken device professionally repaired a decision that paid off. The machine is now back in full operation.
Our Repair and Test Process
- Disassembly and Visual Check: Components inspected for corrosion, cracks, and damage.
- Component-Level Diagnosis: Transistors, drive stages and signal processing verified.
- Cleaning: Full ultrasonic bath, compressed air, and industrial cleaners used.
- Replacement of Faulty Parts: Only genuine Mitsubishi components installed.
- Functional Testing: The unit is tested under real load and machine-like conditions.
Our technicians follow structured checklists, and each step is documented digitally for traceability.
Conclusion
Beware of cheap eBay deals. A seemingly “quick fix” can turn into a costly mistake especially when fake model labels and software mismatches are involved. In this case, repairing the original unit was the smarter and safer option.
Our recommendation: Let your original drives be repaired by professionals. We offer:
- Fixed prices
- Express service
- Genuine spare parts
- Full load testing
More Info & Contact
To mentioned Mitsubishi Drive: MR-J2S-350B-S041U703 AC Servo Drive
More details about our Mitsubishi repair services can be found here:
Mitsubishi drive Repair by Industrypart
We regularly repair similar models, including:
MR-J2S-350A
MR-J2S-350B
Technical Specifications
| Property | Value |
|---|
| Model | MR-J2S-350B-S041U703 |
| Power | 3.5 kW |
| Input Voltage | 1Ph/3Ph 200–230 V, 50/60 Hz |
| Input Current | 16 A |
| Output Voltage | 170 V, 0–360 Hz |
| Output Current | 17 A |
| Weight | approx. 2.0 kg |
Operating Environment and Compatibility
This AC servo amplifier belongs to the MELSERVO J2S Super Series and is commonly used in automated machines, CNC systems or handling technology. It is typically paired with Mitsubishi HC-SFS or HC-RFS servo motors
Recommended conditions:
- Temperature: 0–55 °C
- Humidity: < 90% (non-condensing)
- No exposure to oil, gases or conductive dust
Functional Description
The MR-J2S-350B is a fully digital servo amplifier offering high-precision position, speed and current control. It supports high-resolution encoders (131072 pulses/rev) and uses real-time auto-tuning to automatically adjust to the mechanical load
Main protection functions include:
- Overcurrent shutoff
- Overvoltage shutoff
- Electronic thermal overload relay
- Motor overheat protection
- Encoder error detection and error memory
Alarm Messages & Troubleshooting
| Alarm Code | Meaning | Recommended Action |
|---|
| 10 | Undervoltage | Check power input, replace amplifier if necessary |
| 30 | Regenerative Overload | Check Parameter 2, verify braking resistor wiring |
| 31 | Overspeed | Increase acceleration times |
| 32 | Overcurrent | Check for short circuits or IGBT failure |
| 50 | Overload 1 | Reduce load or extend cycle times |
| 51 | Overload 2 | Inspect mechanics, install limit switches |
| 52 | Excessive Error | Increase braking time, review encoder settings |
Internal Components (from parts list)
| Name | PCB Label |
|---|
| Control Board | J2SB-C01C |
| Power Board | J2S-A07 |
| Load Capacitor Board | J2S-P20A |
| Power Section | (unspecified) |