The Fanuc Power Supply Module
The power supply module in a Fanuc Alpha stack feeds main power and control power to the other units in the chain. A healthy Alpha PSM shows two dashes on its display and puts out about 300 volts DC on the bus. The capacities of the servo and spindle motors on a machine set the PSM size for that machine.
Part numbers for Alpha power supplies start with A06B-6077, A06B-6081, and A06B-6087. Alpha i power supply modules carry A06B-6110 part numbers in sizes from the PSM-5.5i up to the PSM-37i. Fanuc built other versions like the PSMR with a separate regenerative discharge unit and the voltage-converting PSMV-HV.
Fanuc Power Supply Repair Shops
CNC Electronics Inc
Charlottesville, VA
Brands: Fanuc
Lakeside CNC Electronics
Addison, IL
Brands: Fanuc
MRO Electric and Supply
Raleigh, NC
Brands: Fanuc
Northline Industrial
Redford, MI
Brands: Fanuc, Makino, Okuma
Repair Zone
Bay City, MI
Brands: Fanuc
Tri Star CNC Services, LLC
McHenry, IL
Brands: Fanuc
Compare Fanuc Power Supply Repair Shops
This table lists turnaround, warranty, and evaluation terms from each shop's published information.
| Shop | Repair type | Turnaround (business days) | Warranty (months) | Free evaluation | Rush service |
|---|---|---|---|---|---|
| CNC Electronics Inc | Ship-in repair | Not listed | 12 | Not listed | Not listed |
| Lakeside CNC Electronics | Ship-in repair | 2-3 | 12 | Yes | Yes |
| MRO Electric and Supply | Ship-in repair | 2-3 | 12 | Not listed | Not listed |
| Northline Industrial | Ship-in and on-site | Not listed | 12 | Yes | Not listed |
| Repair Zone | Ship-in repair | Not listed | 12 | Not listed | Yes |
| Tri Star CNC Services, LLC | Ship-in and on-site | Not listed | 12 | Not listed | Not listed |
Common Power Supply Failures
Published repair records for Alpha PSM units list leaky capacitors with open circuits and corroded traces. The same records show bad regeneration circuits and failed main power transistors. Bulk capacitor failure on A06B-6087 units tends to show up after 20 or more years of service.
Capacitor wear in the PSM can cause a DC bus undervoltage fault. A failing bulk capacitor can trigger soft overcurrent trips on axis motion and look like a servo amplifier problem. Repair shops list pre-charge circuit faults among the common PSM failures as well.
Input Power Problems
Some power supply alarms come from the incoming plant power and not from a fault inside the module. Alarm 607 on a Fanuc 0i Mate-MC points to a missing AC phase at the DC bus charging circuit. The Alpha i PSM troubleshooting guide lists input voltage imbalance and a mismatched AC reactor among the causes of alarm AL-01.
Machines on rotary phase converters can see voltage imbalance and extra ripple current in the PSM from the converter output. Fanuc sizes the PSM bulk capacitors for about 10 percent line variation and not for the extra ripple from an unbalanced supply. A check of the input power against the PSM specification belongs ahead of any module repair or replacement.
Reading Power Supply Alarms
An Alpha i PSM lights its ALM LED red and shows a one-digit alarm code on the seven-segment display. Alarm AL-01 on smaller units like the PSM-5.5 and PSM-11 points to an error in the IPM power module of the main circuit. On larger units like the PSM-15 through PSM-30 the same code means overcurrent at the main circuit input.
Alarm AL-02 reports a stopped cooling fan for the control circuit inside the module. Alarms AL-06 and AL-07 flag an abnormal input power supply and an abnormally high DC voltage in the main circuit. AL-05 shows up often on a new Alpha PSM install and calls for a check of the bus bar connector at the top of the module.
Repair and Testing for Fanuc Power Supplies
Component-level PSM repair replaces failed capacitors and IGBTs and fixes faults in the pre-charge circuit. The module needs full isolation and a full discharge of the DC bus ahead of any diagnosis on the bench. Some repair shops add heat chamber runs and overnight dynamic testing ahead of shipment.
Older Fanuc controls use a separate control power supply unit like the A16B-1212-0100. This unit lights a red alarm LED on a fault such as an output error and holds the LED on until a reset with the OFF switch. Board repair shops work on these units along with axis boards and I/O modules.