Resolving a power-up fault was only the first step in repairing this FANUC Servo Amplifier A06B-6096-H206. A further fault then became apparent on amplifier channel M. The case illustrates why the behaviour of the drive after an initial repair must also be assessed.

Customer report

The customer reported that the unit displayed alarm “b.” when switched on. At the same time, the control showed “449 IPM Alarm”. We were able to reproduce this initial fault during the incoming inspection.

The subsequently identified fault on channel M was a separate workshop finding. It only became apparent after the power-up fault had been resolved.

Technical data

These values are taken from the supplied nameplate. The 5.3 kW figure is input power, not motor output power. Likewise, 230 V is the maximum output voltage. The L and M channel designations must be distinguished from the machine axis indicated on the CNC. [1]

How the module works

The module supplies two servo motors through channels L and M. Its power electronics produce the controlled motor supply from the DC input. The power output stage and its drive circuitry must work together. A fault in this area can therefore become apparent at power-up or when an attached drive starts. [2]

Findings and repair

First, the reproducible fault involving “b.” and “449 IPM Alarm” was resolved. Further diagnosis then revealed a problem on channel M: the attached drive started only briefly or moved in one direction only. It subsequently stopped with the message “410 – Y Axis excess Err”.

Further investigation identified a defective power output stage. We repaired the circuitry driving that stage. In addition, the entire unit received a preventive overhaul. The work therefore went beyond resetting or acknowledging the initial alarm.

The repair therefore involved two distinct fault patterns: first the fault immediately at power-up, followed by the abnormal starting behaviour of channel M. [1]

Troubleshooting and alarm notes

For traceable troubleshooting, the indication on the module and the message on the CNC should be recorded together. The operating condition is also important: does the fault occur immediately at power-up, on the first start, or later? In this case, the change from a power-up fault to abnormal starting behaviour was particularly informative.

“M” identifies the affected amplifier channel in this report. “Y Axis” is retained as part of the observed CNC message. These designations must not be treated as universally interchangeable without checking the specific machine configuration. An alarm on its own is not proof of a particular failed component; the actual finding came from the workshop investigation.

Testing and prevention

The test video shows the connected module and its associated control on the test bench. The recording provides an insight into this test setup.

With a fault of this kind, another functional check after each significant repair step is useful. Assessment should cover not only power-up but also the behaviour of individual channels and the corresponding control messages. This is the central lesson of the case: resolving a startup alarm can make a further fault visible that could not previously be evaluated.

For maintenance records, capture the complete alarm indications and the conditions in which they occur. Work on power electronics and electrical testing should be carried out by qualified personnel in accordance with the manufacturer’s safety and discharge requirements. Maintenance measures depend on the manufacturer’s requirements and the actual operating conditions.

Sources

[1] Workshop information for this repair case, supplied before/after photographs, nameplate photograph and the original test recording “A06B-6096-H206 Video Test.mp4”.

[2] FANUC / GE Fanuc, Alpha Series Motors and Modular Drives, Maintenance Manual B-65165E/02 / GFZ-65165E/02, June 2000: model identification on printed page 12, alarm overview on page 100 and IPM alarm section 3.2.2 on page 130. Manufacturer document hosted by a document mirror. The 410 message is reproduced solely as a workshop observation, not as a code explanation taken from this manual.

Video

The test footage shows the setup used for this repair case.

Repair photographs

Repair enquiry and further information

Does your FANUC A06B-6096-H206 show a fault at power-up or abnormal starting behaviour? For a technical assessment, please provide the full model designation, a photograph of the nameplate, the amplifier indication and the CNC message. A short description of when the fault occurs is also helpful.

Information about repair options, pricing and lead time is available on the matching FANUC A06B-6096-H206 product page, in German. The required work depends on the findings from the submitted unit.