Yaskawa SGMG-09V2ABC: encoder replacement and complete overhaul

This Yaskawa AC servo motor arrived at industrypart with a suspected encoder fault. From approximately 1,000 rpm it produced pronounced noise, sounding as though it was continually trying to correct its motion. We replaced the encoder, overhauled the motor and subsequently carried out extensive testing and adjustment. The serviceable brake was cleaned and retained.

Motor identification and nameplate data

The electrical ratings and serial number above come from the supplied motor nameplate. Encoder and brake designations are documented in the repair information. The nameplate speed is a rated operating point, not a statement of maximum permissible speed. The 200 V motor rating and the separate 24 V DC brake supply must not be confused.

Application, interfaces and replacement compatibility

The servo motor converts the amplifier’s controlled electrical output into shaft torque. Its feedback system supplies the motion information needed by the control loop. Power, feedback and brake functions must be matched to the actual machine wiring and amplifier configuration. This repair report does not establish a particular machine model or SERVOPACK pairing.

A similar housing or the same power rating alone is not sufficient for replacement selection. Check the complete suffix, mounting geometry, shaft, connector assignments, feedback interface, brake voltage and the approved motor data. The UTOPH-81AWF to UTOPH-81AiF replacement described here is a documented workshop action for this unit, not a blanket interchangeability statement for all applications.

Components and their diagnostic significance

Why feedback faults can sound like a mechanical problem

The command specifies the requested movement. The encoder reports actual motion to the servo amplifier. The controller uses the difference to adjust motor current and torque. Unreliable feedback can therefore cause inappropriate corrections that are audible or felt as vibration. That mechanism explains why the reported sound was relevant to the encoder suspicion; the sound alone does not identify an encoder defect.

Mechanical noise may also arise from bearings, coupling alignment, driven machinery or a brake that does not release fully. Cable faults, poor contacts, shielding problems and unsuitable control settings can affect the same system. Recording the onset speed and comparing operation under defined conditions helps separate these possibilities. In this case, the confirmed work comprised encoder replacement and a complete mechanical overhaul; no individual signal measurements or load-test values were supplied.

Practical diagnostic guide and alarm assignment

No specific alarm code was reported for this case. Alarm numbers are assigned by the connected servo amplifier and its software, not by the motor model alone. The following table is a diagnostic guide, not a code list for an unidentified drive. For an exact alarm interpretation, record the amplifier model, complete display, operating state and alarm history.

Repair, adjustment and testing

We replaced the UTOPH-81AWF encoder with a new UTOPH-81AiF. The complete overhaul included new ball bearings and seals, thorough cleaning and repainting. The SBR-112V-130B brake was found to be in order and was cleaned without replacement. After reassembly the motor underwent extensive testing and adjustment.

Feedback adjustment matters because mechanically fitting a replacement encoder is only part of the task. The motor and control system must also receive the correct motion relationship. The supplied test recording documents operation on the test setup. It does not establish a quantified load capacity or a specified endurance-test duration.

Preventive maintenance with practical benefit

Keep cooling surfaces and connector areas clean, protect seals from contamination and inspect cables for damage or strain. Compare operating noise over time under similar conditions. Record the speed at which a change begins, together with load, temperature and any amplifier alarm. Check the brake’s release function using the machine-specific procedure. These observations make a later diagnosis more focused than the description “motor is noisy”.

Technical reference

Yaskawa Sigma Series SGM*/SGDB User’s Manual, SIE-S800-26.4C, sections 4.4, 5.8, 5.9 and 12, provides general family-level information on feedback, brake interlocking, adjustment and maintenance. Its variant-specific ratings and SGDB alarm codes are not transferred to this undocumented drive pairing. Exact motor values above are taken from this unit’s nameplate.

Test video

Before and after repair

Request a repair assessment

Please send the complete motor designation, a nameplate photo, the amplifier model and a description of when the symptom occurs. Mention the speed threshold, load conditions and any alarm display. industrypart supports you with diagnosis, repair and preventive overhaul of industrial motors and drive electronics.

Yaskawa SGMG-09V2ABC AC Servo Motor

For more information about our Yaskawa motor and drive repairs, visit our Yaskawa repair service.