06.07.2025 by Viktor Siebert
When the Encoder Fails. How We Rescued a Yaskawa SGMGH-13ACA6S Motor in Record Time
A customer personally brought in his Yaskawa SGMGH-13ACA6S servo motor. The reason? The connected Servopack kept randomly showing alarm AC.9 Encoder Communication Error.
At first, the customer suspected faulty cables and replaced them, but it didn’t help. Next, he swapped the Servopacks between axes still, the same axis showed the error. Then he exchanged the encoders between the X and Y axes (both motors were identical) and suddenly the fault followed the encoder.
That confirmed it: the encoder was the issue.
Manufacturer Support? Not Really.
The customer contacted both the machine manufacturer and Yaskawa directly. The result was disappointing:
- The machine builder offered an overhaul but it would take over a month, as the motor had to be shipped to Japan.
- Yaskawa simply referred back to the machine manufacturer.
- The quoted repair cost exceeded the price of a new motor.
The customer was visibly frustrated:
“I need to keep producing. This situation is killing me. The machine kept crashing, and every time the workpiece was ruined. I can’t go on like this.”
The Solution Came Through a Recommendation.
Through a recommendation, the customer found his way to us. We received the motor the same day and began diagnostics immediately. The result: the encoder was defective and unable to provide stable feedback.
Our Repair Process Precise, Fast, Reliable
- Disassembly & Inspection
The motor was fully dismantled, cleaned, and checked for further damage — especially for thermal stress or bearing wear.
- Encoder Replacement
The old encoder was completely removed. We installed a brand-new original encoder (UTSIH-B17CK) exactly matched for this motor type.
- Encoder Programming
This step is crucial: the encoder is not just mounted mechanically it is software-configured precisely for this specific motor. Without this step, the Servopack won’t recognize or control the motor properly.
- Functional Testing
The repaired motor was tested on our in-house test bench using a Yaskawa SGDH-15AE-OY Servopack. We verified:
- Precise positioning and zero-point accuracy
- Temperature behavior under load
- Current consumption
- Encoder signal integrity
- Insulation resistance and grounding
- Final Check & Documentation
After a successful 100% test, the motor was sealed and returned only four days after drop-off.
The Result? Production Back On and Plans for More.
One week later, the customer called us back:
“Everything’s been running perfectly since reinstalling the motor. I’m now thinking about having you overhaul the servo drives too. Especially with the summer heat these drives are really under strain. I’m taking company holidays in August that’s the perfect time to get them serviced.”
Conclusion: Time is Money, Precision Builds Trust
This story is a great example of how fast, competent service can get production back on track. We not only understand the technology, we understand what our customers are going through.
Information about the mentioned Servopack and Servomotor:
More information about our Yaskawa repairs can be found here.
📞 Feel free to contact us if you have any questions regarding your Yaskawa drive technology. Our experienced team is always ready to assist you.
Technical Specifications Yaskawa SGMGH-13ACA6S
| Specification | Value |
|---|
| Model | SGMGH-13ACA6S |
| Series | Sigma II |
| Rated Power | 1.3 kW |
| Rated Torque | 8.34 Nm |
| Peak Torque | 23.3 Nm |
| Rated Speed | 1500 RPM |
| Maximum Speed | 3000 RPM |
| Rated Current (RMS) | 5.4 A |
| Max. Current (RMS) | 14 A |
| Voltage | 400 V AC |
| Encoder | Incremental 17-bit (UTSIH-B17CC) |
| Insulation Class | F |
| Protection Class | IP67 (excluding shaft opening) |
| Mounting | Flange-mounted |
| Weight | ~13.5 kg |
| Shaft | Straight, with key and tapped center |
| Cooling | Self-cooled, totally enclosed |
Alarm Codes & Troubleshooting Sigma II
| Alarm Code | Alarm Name | Description | Recommended Action |
|---|
| A.02 | Parameter Breakdown | EEPROM data error in servo amplifier | Re-initialize amplifier or replace it |
| A.04 | Parameter Setting Error | Parameter value out of allowable range | Check and correct parameter settings |
| A.05 | Servo Motor / Amplifier Mismatch | Motor and amplifier capacity do not match | Verify compatibility (e.g. SGDH-15AE + SGMGH-13ACA6S) |
| A.10 | Overcurrent / Heat Sink Overheated | Excessive current or heat sink temperature too high | Check cooling, fan, ventilation, reduce load or replace drive |
| A.30 | Regeneration Error | Fault in regenerative circuit or resistor | Check wiring and resistor function |
| A.32 | Regenerative Overload | Regenerative energy exceeds resistor capacity | Optimize cycle or use higher-rated resistor |
| A.40 | Overvoltage | Main DC bus voltage too high | Check input voltage, avoid regeneration spikes |
| A.41 | Undervoltage | Main DC bus voltage too low | Verify input power source |
| A.71 | Overload: High Load | Short-term torque overload | Check mechanical load, reduce acceleration/torque |
| A.72 | Overload: Low Load | Long-term continuous torque overload | Adjust mechanical setup or use higher-rated motor |
| A.C1 | Servo Overrun | Motor lost control, exceeded speed or position limits | Check feedback loop, tuning parameters, wiring |
| A.C9 | Encoder Communication Error | No encoder signal received or communication error | Check encoder, cables, and signal integrity |
| A.bF | System Alarm | Internal system fault in servo amplifier | Contact support or replace drive |
