Mitsubishi HS-xF AC Servo Motor Repair Experts

Here at Precision Zone, we specialize in Mitsubishi product repairs servicing a wide range of AC servo motors. One series that we work on quite often is the Mitsubishi HS-xF series AC servo motor.

The HS-xF series of AC servo motors from Mitsubishi is offered in multiple options to assist with many different applications. These can include the servo drive directly with it or be offered as a standalone intelligent servo motor. A built-in dynamic brake is a standard feature on these motors as well. There are low-inertia, small or medium capacity options which cover HS-MF23, HS-RF43, and HS-RF73. The specifications of these can be seen below.

Type HS-MF23 AHS-RF42 HS-RF73
Rated Output 0.2kW / 15 Min
0.15kW / Continuous
0.4kW / 30 min
0.32kW / Continuous
0.75kW / 30 min
0.3kW / Continuous
Rated Speed 3000 rpm 3000 rpm 3000 rpm
Detector Resolution 8,000/absolute value 100,000/aboslute value 100,000/absolute value
Required Voltage Single-phase 200 VAC to 230 VAC 50/60Hz Three-phase 200 VAC to 230 VAC 50/60HZ Three-phase 200 VAC to 230 VAC 50/60HZ

Additionally, there is also medium-intertia, medium-capacity variations available within this series

Type HS-SF23 AHS-SF53 HS-SF102 HS-SF103 HS-SF202
Rated Output 0.5kW / 30 Min
0.4kW / Continuous
0.5kW / 30 min
0.4kW / Continuous
1.0kW / 30 min
0.75kW / Continuous
1.0kW / 30 min
0.75kW / Continuous
2.0kW / 30 min
1.5kW / Continuous
Rated Speed 2000 rpm 3000 rpm 2000 rpm 3000 rpm 2000 rpm
Detector Resolution 100,000/absolute value 100,000/aboslute value 100,000/absolute value 100,000/absolute value 100,000/absolute value
Required Voltage Three-phase 200 VAC to 230 VAC 50/60HZ Three-phase 200 VAC to 230 VAC 50/60HZ Three-phase 200 VAC to 230 VAC 50/60HZ Three-phase 200 VAC to 230 VAC 50/60HZ Three-phase 200 VAC to 230 VAC 50/60HZ

When assessing the functionality of a motor, our engineering team typically conducts a six step check:

    1. Visual Overview
    2. Static Test
    3. Back EMF
    4. Feedback Check
    5. Alarm Code Troubeshooting
    6. Disassembly and Cleaning

This overview is Precision Zone’s basic troubleshooting process. Once our repair team starts on the job we use specialized, customized test fixtures, SKF Baker AVAIV-4, Huntron devices, signal generators, oscilloscopes, milli and mega ohm meters, and other necessary tools to assure quality repair.

Most importantly, every repair is fully tested in custom-built simulators under load to replicate real-life working conditions.

Repair Process for Mitsubishi HS-xF Series AC Servo Motors

Visual Overview

When conducting a visual check, the technician inspects the motor for any mechanical damage to the power connecter, junction box, rotor shaft, oil seals and encoder covers. During the visual inspection the technician notes excessive dirt, oil or grease on cooling fans and all other parts of the motor.

Static Check Basic

Precision Zone repair technicians use an SKF Baker Advanced Winding Analyzer to fully evaluate the stator winding. The SKF Baker performs a wide range of electrical tests, including surge, DC hi-pot, mega-ohm, and winding resistance tests. In the instance of winding resistance each phase is tested with each other; and the mega ohm readings should be no less than 200 mega ohms.

Winding Resistance Testing

Positive Lead Negative Lead Approximate Reading
U V 0.2Ω - 10Ω¹
V W 0.2Ω - 10Ω¹
W U 0.2Ω - 10Ω¹

¹ Reading should be balanced, 10% difference maximum, between all three phase combinations.

Mega Ohm Testing

Positive Lead Negative Lead Approximate Reading
U Ground/Unpainted stator area Well above 200 MΩ ²
V Ground/Unpainted stator area Well above 200 MΩ ²
W Ground/Unpainted stator area Well above 200 MΩ ²

² Our recommended minimum is 200 MΩ. Anything close to that 200 MΩ reading can still cause issues as the motor heats up and that value begins to drop lower.

Back EMF Check

If a servo motor passes the static checks it will be back driven and have the back EMF checked. With our in house magnetizing service we can bring back to life servo motors with weak magnets.

Feedback Check

Repair technicians can test encoders in a number of different ways. Our Mitchell Electrics TI-5000EX system can be used to read, write and record encoder count and data information. We have Mitchell Electrics TI-5250 systems that can be used to see live encoder pulses on an oscilloscope. Connecting encoders directly to the manufacture’s drive is another way we can verify if an encoder is working correctly.

Disassembly and Cleaning

All motors are fully dissembled, washed, and baked. Rotors are checked for bent shafts and bearing journal common problems. The stator winding is rechecked after the baking process. Holding brakes are refurbished and the holding torque is checked. Both the drive end and opposite drive end housing bearing surfaces are checked. Once the evaluation is completed a computer report is generated with all the findings.

Common Failures and Troubleshooting with Mitsubishi AC Servo Motors

Failure Type Common Cause Troubleshooting
Overcurrent Poor motor or cable insulation, phase to phase, short, phase to ground short
  • Perform mega ohm test, first through cables, then at motor terminals (if applicable)
  • Perform winding resistance test
  • contact Precision Zone for further troubleshooting
Encoder related alarms Encoder failure, issue with feedback cabling, control board failure on drive side
  • Check encoder waveforms if oscilloscope and back-driving of motor is available
  • Connect motor with a different drive if applicable, contact Precision Zone support for further information
Motor shaft is locked up Demagnetization occurred, brake malfunction (where applicable), drive side fault
  • Disconnect motor from drive and attempt to spin by hand, if no brake is used
  • If brake is used, verify that it is disengaging appropriately
  • Contact Precision Zone support for further troubleshooting

This list of checks for certain alarms is primarily a good starting point and if any further troubleshooting or technical support is needed, feel free to contact us via phone or email to get in touch with our experienced tech support team.

Precision Zone offers free technical support on any component that you may be having issues with. We understand that when your machine goes down, your business stops. That is why our number one goal is to provide you with the best service possible so that you can get back up and running immediately. For any further product information or troubleshooting assistance is needed, please contact us via phone at 800-551-4420 or email us.

Precision Zone Repair Benefits for Mitsubishi HA-FF AC Servo Motors

  • Free quotes and evaluations by our expert technicians include:
  • 12-Month Warranty on Our Parts and Labor
  • Decades of Industry Experience
  • Exchange Options
  • Rush Service Options

Contact Us To Start Your Repair Today!


Recently Repaired Products

Mitsubishi HS-MF23EXV-S2 image HS-MF23EXV-S2 is an
Motors-AC Servo manufactured by Mitsubishi
Discovered issues: Full of Oil Inside
Servomotor Type: Intelligent servomotor HS-MF Series; ultra-low inertia,small capacity
Rated Output: 0.2kW
Rated Speed: 3000 rpm
Electromagnetic brake: none
Amplifier type: With amplifier-encoder for NC, new version
Motor special symbol: S2

Mitsubishi HS-MF23EX-S2 image HS-MF23EX-S2 is an
Motors-AC Servo manufactured by Mitsubishi
Discovered issues: Bad Start/Run Capacitor
Servomotor Type: Intelligent servomotor HS-MF Series; ultra-low inertia,small capacity
Rated Output: 0.2kW
Rated Speed: 3000 rpm
Electromagnetic brake: none
Amplifier type: With amplifier-encoder for NC
Motor special symbol: S2

Mitsubishi HS-RF73NX-S2 image HS-RF73NX-S2 is an
Motors-AC Servo manufactured by Mitsubishi
Discovered issues: Bad Encoder
Servomotor Type: Intelligent servomotor HS-RF Series; low inertia,medium capacity
Rated Output: 0.75kW
Rated Speed: 3000 rpm
Electromagnetic brake: none
Amplifier type: NX
Motor special symbol: S2

Mitsubishi HS-RF43B-S1 image HS-RF43B-S1 is an
Motors-AC Servo manufactured by Mitsubishi
Discovered issues: Full of Oil Inside
Servomotor Type: Intelligent servomotor HS-RF Series; low inertia,medium capacity
Rated Output: 0.4kW
Rated Speed: 3000 rpm
Electromagnetic brake: with brake
Motor special symbol: S1