02.06.2025 by Viktor Siebert
Error Code 993 – Internal Short Circuit HAAS Servo Amplifier 90A (part number 93-32-5549)
Recently, we repaired a HAAS Servo Amplifier 90A (part number 93-32-5549). The error displayed on the machine screen was 993, indicating an internal short circuit in the amplifier.
When we opened the unit, everything looked fine at first – no burnt components. However, the short circuit was measurable directly on the transistor module.
Root Cause: Overvoltage from the Vector Drive
We contacted the customer to ask what had happened. The question wasn’t random – since these amplifiers are powered directly by the Vector Drive, it’s almost always an overvoltage from the Vector Drive that damages the amplifiers connected to it.
The customer confirmed that the machine had been showing issues for some time – especially in the mornings or after weekends. They had to let the machine run for about half an hour before it reached the required voltage, and various errors were shown.
The Real Culprit: Defective Vector Drive
We were already familiar with this type of issue. It clearly indicated that the HAAS Vector Drive was most likely the actual source of the failure – and had probably already been faulty for a while. Most likely, it caused the failure of the amplifier.
One of our sales representatives called the customer to explain the situation and warned that other axis amplifiers could also be affected. In many cases, multiple devices are damaged.
Quick Customer Action
The customer decided to send us the Vector Drive along with all other amplifiers. Fortunately, aside from the 90A Servo Amplifier, none of the other units were damaged. The Vector Drive, however, showed the well-known and common faults.
Repairs on the Vector Drive and Amplifier
We carried out a full overhaul of the Vector Drive. The HAAS 90A Servo Amplifier also received a complete rebuild, including:
- Replacement of the transistor modules
- Repair of the control stage
- Replacement of optoelectronic components
- Renewal of the electrolytic capacitors and other critical parts
Both devices were thoroughly tested in our in-house test machine, allowing us to guarantee their reliable performance in the customer’s system.
Satisfied Customer and Preventive Maintenance
Thanks to this proactive approach, the customer was able to avoid further trouble. A short while later, we received feedback: “Everything is running perfectly.”
The customer also mentioned he would like to have other axis amplifiers overhauled preventively. Since he is planning a summer vacation, he plans to send us the remaining devices during that time. He values reliability and wants to avoid such failures in the future – and is willing to take preventive steps to ensure it.
To mentioned HAAS Drive: HAAS Servo Amplifier 90A Teilenummer 93-32-5549 oder 32-5549
More details about our HAAS repair services can be found here:
HAAS drive Repair by Industrypart
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Our expert team is happy to help!
Technical Specifications – HAAS Servo Amplifier 90A (P/N 93-32-5549)
| Specification | Description |
|---|
| Model Number | 93-32-5549 |
| Rated Output Current | 90 A |
| Input Voltage | 320 VDC (supplied by Vector Drive or MiniMill power supply) |
| Application Type | BL SMART Amplifier for CNC axis drive |
| Indicators | Red LED (Fault), Green LED (Status/Power) |
| Cooling Method | Passive with optional external fan |
| Weight | Approx. 1.8 kg (4 lbs) |
| Mounting Type | Panel-mounted inside electrical cabinet |
| Compatible Motors | HAAS servo motors (varies depending on axis size and machine type) |
| Typical Machines Used In | CNC milling machines, lathes, MiniMill, Super MiniMill, etc. |
Common Alarms & Troubleshooting – HAAS 90A Servo Amplifier
| Alarm Code | Description | Possible Causes | Recommended Actions |
|---|
| 991 | Amplifier Overheat | Inadequate cooling, blocked ventilation, failed fan | Check for proper airflow, verify fan operation, clean ventilation filters |
| 992 | Amplifier Overcurrent | Shorted motor cable, jammed axis, defective motor | Inspect motor cables and connections, check for mechanical axis binding |
| 993 | Amplifier Short Circuit | Internal short in IGBT module or amplifier control circuit | Disconnect and test amplifier; replace if short is confirmed |
| 994 | Amplifier Overload | Excessive load on axis, incorrect tuning or command overload | Reduce axis load, verify parameters, inspect for mechanical resistance |
| 986 | Calibration Error | Amplifier unable to auto-calibrate internal reference | Check control signals, verify 320 VDC bus supply, replace if error persists |
| 9911 | Axis Amplifier Disconnected | Signal loss between control board and amplifier | Inspect amplifier communication cable, re-seat connectors, replace damaged cable |
