Recent Job Report #4 -FANUC Alpha i Series AC Servo Motor Repair

Fanuc A06B-0265-B102

Here is a Fanuc Alpha i servo motor ready for assembly.

Repair Zone has been seeing an influx of newer generation Fanuc Alpha i Series servo motors and drives coming in for repair.  An Aerospace parts manufacturer in California sent us this Fanuc A06B-0265-B102 Alpha i servo motor for evaluation because it was increasingly noisey.  In our initial evaluation, all testing showed no major damage to it.  This motor will receive a standard reconditioning, which includes new bearings and new seals, full cleaning, feedback alignment, testing, etc.  The pictorial below follows Scott, a Fanuc specialist, as he takes us through this repair.  If you need a repair of your servo equipment, or have any questions, please call 1(989) 922-0043 for immediate service.  To browse our Fanuc inventory, go to


Fanuc Alpha i Series Servo Motor repair

Scott begins by testing the resistance to ground, which is done by using a Megger – tested good!

Fanuc servo motor testing

Back EMF test – 46.1 volts, line to line. Tests good!

Fanuc Alpha i AC servo motor

Removing back end bell and encoder.

Fanuc Alpha i AC servo motor

Scott visually inspects the encoder and its bearings.

Fanuc servo motor repair

Connected to our software, Scott measures the accuracy of the encoder counting – it was found to be counting correctly and in factory specifications.

Fanuc Alpha i

Scott is testing to see if thermal on encoder is closed.

Fanuc Repair

The technician is preparing to pull the back end bearing from the rotor.

Servo Motor Repair

Servo is fully disassembled.

Fanuc servo motor Alpha i repair

Surge testing the phases in the stator before and after cleaning.  If any of the 3 phases were shorted, it would need to be rewound.  In this case, all 3 phases were good as well as the insulation strength.

Fanuc repair

A pre-wash is sprayed onto the windings and stator. Each servo is washed twice; once to remove heavy contamination and a second time it is placed into a parts washer for more thorough cleaning.  It is then baked overnight in our oven.

Fanuc motors

Removing heavy contaminants via power washing.

Fanuc servo motors

Beginning the assembly process.

Fanuc A06B servo motors

Applying sealant to keep out moisture and contamination.

Fanuc servo repair

Closely inspecting windings, leads, and thermals.

Fanuc Repair

Stator is ready to insert rotor and install new bearings.

Fanuc servo motor repair

Fully assembled and awaiting final run-test.

Fanuc Alpha i AC Servo Motor

Scott applied paint and ‘blue-dyes’ the shaft giving it a like new appearance.

Fanuc servo motors

Each servo is run-tested twice, once in the beginning and at the end to finish the repair.  It’s run data was good and had 6.0 amps, 215.1 volts.

Fanuc repair

This Fanuc Alpha i AC servo motor is Ready to Ship!

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Fanuc repair at Repair Zone

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  1. Love the in-depth walkthrough for this repair! My business has needed some repairs in the past, and this sheds a lot of light on the process. What do you suggest for concrete polishers? There’s a concrete polisher in Utah that we’ve looked into, but do you have any experience with that?

    • Hi Christian,

      Thanks for your question. I do not have any expertise in the area of concrete polishers, but all things servo motors and amplifiers in relation to those I can help! If you have any specific questions about servo equipment, please let me know.

      Thanks again!
      Jade York

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