15.11.2026 by Viktor Siebert
Okuma MIV08DB-1-B5: not working, fan failure and power stage repair
Not working: this Okuma MIV08DB-1-B5, reference 1006-2266, was repaired following damage to the power output stage and a failed cooling fan. The loss of cooling may have contributed to excessive thermal stress in the power section. Our overhaul included both fans, capacitors and a hybrid component alongside the repair. The work order was completed as repaired and tested.
Fault condition and assessment
The relevant fault condition was a complete loss of function. A cooling fan was also defective. A connection between fan failure and power stage damage is plausible, but the exact sequence cannot be conclusively established for this unit. We therefore distinguish the confirmed damage from its suspected origin.
A stopped fan can significantly reduce heat removal. If heat builds up in the power section, component stress increases. Once a drive has failed, the inspection must establish whether other components have been damaged in addition to the fan. Simply replacing the fan would then be an incomplete repair.
Device information
| Item | Details |
|---|
| Manufacturer | Okuma |
| Device | Servo Drive / MIV inverter |
| Full model | MIV08DB-1-B5 |
| Reference | 1006-2266 |
| Device marking | U:1.0 |
| Fault condition in this case | Not working, failed fan, damaged power output stage |
| Result | Repaired, overhauled and tested |
Role within the drive system
The MIV module forms part of the Okuma Motion Control System. It controls the connected motor together with the CNC, feedback system and separate DC power supply. The power output stage provides the motor currents. Reliable operation depends on the power section, control circuitry, supply and cooling working together.
The complete model designation, including its suffix, matters when selecting a replacement. A similar-looking MIV module is not automatically suitable. The machine, motor, control and device version must be checked as a combination before installation.
Repair and preventive overhaul
The drive was dismantled and thoroughly cleaned. The components listed below were replaced during repair and overhaul. This list records the work on this particular device; it is not a universal replacement list for every MIV module.
| Replaced component | Quantity |
|---|
| Electrolytic capacitors | 17 |
| Main capacitors | 3 |
| Internal cooling fan | 1 |
| External cooling fan | 1 |
| AF9592B hybrid component | 1 |
Replacing both fans addresses internal airflow and cooling of the power section. The capacitors were renewed as part of the overhaul. The work therefore extended beyond the failed fan alone. The power output stage and associated electronics were repaired as part of the complete drive.
Troubleshooting: record the complete indication
No specific initial alarm code is confirmed for this repair case. The following selection provides general guidance from Okuma manual 4184-E. These are possible indications in this system family, not faults observed on this particular unit. The prefix, number and additional data must be interpreted together.
| Indication / number | Meaning |
|---|
| EL/EH 13 | Inverter bridge fault |
| EL/EH 12 | Gate signal fault |
| AL 01 | Power supply unit fault |
| AL 02 | Converter link fault |
| AL 03 | DC bus voltage fault |
| AL 04 | Motor power line overcurrent |
| AL 05 | Inverter overheating |
| AL 06 | Inverter overload |
| AL 10 | Encoder communication fault |
| AL 11 | Encoder fault |
For the MIV08DB-1, the manual specifically links a faulty external fan with a possible EL/EH 13 indication. This supports the technical plausibility of the suspected overheating. It does not establish that this code appeared in this case, or that every inverter bridge fault is caused by a fan.
Testing and maintenance
The unit was tested after repair. An original recording of the CNC functional test is available for this work order and appears in the video at the end of this article. No particular endurance-test duration or load rating is inferred from this recording.
Regular checks of fan operation, air passages and contamination are useful for maintenance. Unusual fan noise, weak airflow or recurring temperature messages should be investigated. After a failure, the power supply, connections and possible consequential damage also need assessment. Before replacement, record the nameplate, device version and full fault indication. Work on an open drive requires qualified personnel and attention to stored DC-bus energy.
Sources and technical documentation
The case is based on the repair documentation, the supplemented fault description and photographs of this unit. Technical reference: Okuma Drive Unit Motion Control System, Maintenance Manual 4184-E-R6, sections covering the MIV unit, status indications and external fan. https://s3.amazonaws.com/Icarus/DOCUMENTS/Okuma_Manuals_2902.pdf
Photographs before and after repair
Okuma MIV08DB-1-B5 before repair, showing connections and housing.
Second original view before overhaul.
Okuma MIV08DB-1-B5 after repair, front view.
Overhauled Okuma servo drive, side view after repair.
Okuma MIV08DB-1-B5 nameplate, reference 1006-2266.Request repair or exchange
Need support with an Okuma MIV08DB-1-B5? Send us the full model designation, a nameplate photograph and a description of the fault. Industrypart in Bensheim provides repair, overhaul and testing of industrial drives. The matching product and enquiry form are available here: https://www.industrypart.com/de/products/okuma-miv08db-1-b5-or-1006-2266-servo-drive-40997.html. Contact: [email protected], telephone +49 6251 9888430.
Video: repair and CNC functional test
Watch on YouTube