FANUC SV0607 means that the common power-supply or converter module detected an abnormal input power condition caused by an open phase. On the applicable FANUC αiPS or αiPSR power-supply module, the status display shows alarm E.
FANUC Maintenance Manual B-65285EN/04 directs technicians to check the input power-supply voltage first. If the voltage is normal, the next official action is to check the power connections. This makes the incoming three-phase supply, upstream switching devices, terminals, and power wiring the primary diagnostic path.
| Alarm location | Display | Meaning |
|---|---|---|
| CNC | SV0607 / converter main power open phase | The converter detected an abnormal input power condition |
| Applicable αiPS or αiPSR | E | Input power supply abnormal because of an open phase |
| Related spindle alarm | SP9004 / SSPA:04 | Open phase in the converter main power supply |
| Official repair direction | Voltage and connection checks | Check input voltage; if normal, inspect the power connections |
For surrounding servo and converter alarm numbers, see the FANUC SV Alarm Codes: Servo Amplifier, Drive, Voltage and Overheat.
What Does FANUC SV0607 Mean?
The FANUC common power-supply module receives the machine's three-phase AC input and creates the DC link used by the connected servo and spindle amplifiers. All required input phases must be present and within the specification for the installed module.
An open phase means that one phase is missing or is not reaching the converter correctly. The condition can be complete, such as an open fuse or disconnected conductor, or intermittent, such as a loose terminal or deteriorated contactor pole that opens under vibration or load.
Common fault areas include:
- One incoming AC phase is absent
- An upstream fuse, breaker pole, or protective device is open
- A main power terminal is loose, burned, or incorrectly connected
- A conductor is broken, damaged, or intermittently open
- One pole of the main magnetic contactor is not closing correctly
- The contactor control circuit does not energize the contactor completely
- A transformer or upstream distribution component has a phase fault
- Input voltage is severely unbalanced or unstable
- The supplied frequency or voltage is outside the specification of the installed power-supply module
- The converter's input-power detection circuit is defective
FANUC's official alarm-E procedure specifically identifies open phase and directs the technician to check voltage and connections. Frequency abnormality, phase imbalance, MCC faults, and internal detection failure are useful supplementary diagnostic branches, but they should be confirmed with measurements rather than assumed.
Why Several Axes and Spindles May Alarm Together
The common power supply feeds multiple servo and spindle amplifiers through the shared DC link. A single input-power fault can therefore generate alarms for several controlled axes and spindles at the same time.
The supplied alarm-screen example shows:
- SV0607 on the X axis
- SV0607 on the Z axis
- SP9004 / SSPA:04 on spindle S1
- SP9004 / SSPA:04 on spindle S2
This pattern strongly indicates a shared converter or incoming-power problem. It does not mean that the X-axis amplifier, Z-axis amplifier, and two spindle amplifiers all independently developed the same fault at the same moment.
When several channels report the condition together, begin at the common power-supply input and its upstream circuit. Replacing individual servo or spindle amplifiers before checking the shared supply is unlikely to address the primary fault.
Safety Before Troubleshooting
SV0607 troubleshooting involves hazardous three-phase AC power and the high-voltage DC link. Voltage measurements and energized tests must be performed only by qualified electrical personnel using the applicable FANUC and machine-builder procedures.
Before inspecting terminals, cables, fuses, contactors, or the power-supply module:
- Stop the machine using the approved procedure.
- Isolate the incoming power and apply lockout/tagout where required.
- Wait the specified DC-link discharge time.
- Confirm that the charge indicator is off and verify a safe condition.
- Use instruments, probes, and personal protective equipment suitable for the circuit voltage and fault-energy level.
- Do not tighten, disconnect, or move main-power conductors while energized.
- Do not bypass fuses, breakers, phase monitoring, contactors, or safety interlocks.
A fuse must never be replaced with a higher rating merely to prevent recurrence. Determine why it opened and use only the specified replacement type and rating.
1. Confirm SV0607, Alarm E, and Related Alarms
Before switching off the machine, photograph the CNC alarm page and every amplifier display. Confirm:
- The CNC shows SV0607.
- The common power-supply module shows E.
- Any spindle channel shows SP9004, SSPA:04, or another related power-supply message.
- The alarm affects one channel or several axes and spindles simultaneously.
- No earlier alarm identifies a different initiating condition.
Record when the alarm occurs:
- Immediately at machine power-on
- When the main contactor is commanded on
- Only when a spindle or axis begins moving
- During high-load machining
- Intermittently with cabinet vibration
- After electrical, transformer, contactor, wiring, or power-supply work
- Following a facility power interruption or utility disturbance
The following image shows a real example of SV0607 on two servo axes together with SP9004 on two spindle channels. It is a useful reference for recognizing a shared converter-input fault.
FANUC CNC alarm screen showing SV0607 on the X and Z axes and SP9004/SSPA:04 on spindle channels S1 and S2.
2. Inspect the Upstream Three-Phase Supply
With the system safely isolated, trace the converter input back through the machine's electrical drawings. Depending on the machine, the circuit can include a facility disconnect, transformer, breaker, fuses, line reactor, electromagnetic compatibility filter, main magnetic contactor, and terminal blocks.
Inspect for:
- A tripped breaker or open fuse
- A fuse indicator showing operation
- Burned, darkened, cracked, or heat-damaged fuse holders
- Loose or missing conductors
- Discolored or overheated terminals
- Corrosion, coolant, oil, or conductive contamination
- A recently replaced cable connected to the wrong terminal
- Damage near cable bends, glands, and strain-relief points
- Evidence of arcing at the main contactor or terminal block
Do not reset a protective device repeatedly. A breaker trip or blown fuse can indicate a short circuit, ground fault, overloaded component, loose high-resistance connection, or failed downstream device. Find and correct the cause before restoring power.
3. Measure the Input Power-Supply Voltage
FANUC's first official action for alarm E is to check the power-supply voltage. A qualified technician should measure all phase-to-phase voltages at the appropriate test points using the procedure and electrical diagram for the exact machine.
Confirm that:
- All three phases are present
- Each phase-to-phase voltage is within the specified range
- The three measurements are reasonably balanced within the equipment specification
- Voltage remains stable when the main contactor closes
- Voltage does not collapse when the machine begins operating
- The supply frequency matches the installed power-supply specification
A normal voltage measured upstream does not prove that all three phases reach the power-supply input. Measure at the locations permitted by the machine procedure and compare the supply side and load side of fuses, contactors, and terminal blocks.
If one phase is missing upstream of the machine, the facility supply, disconnect, transformer, or distribution circuit must be corrected. If all phases are present upstream but one phase is missing at the converter input, continue tracing through the machine circuit until the open point is found.
4. Check Main-Power Terminals and Cables
If voltage is correct at the incoming source, FANUC instructs technicians to check the connections. With power isolated and discharged, inspect the complete main-power path to the common power supply.
Check for:
- Loose terminal screws or lugs
- Conductors not fully inserted into a terminal
- Incorrect phase or terminal arrangement after maintenance
- Broken cable strands or conductors
- Heat-damaged insulation or terminals
- Oxidized or contaminated contact surfaces
- Damaged crimp terminals
- Cable movement that causes the alarm to appear or disappear
- Improperly seated connectors on designs that use removable power plugs
Use the specified tightening torque and approved termination method. A connection that appears visually normal can still have excessive resistance and fail under load. Replace burned or mechanically damaged terminals rather than merely tightening them.
If continuity testing is required, isolate the circuit correctly and follow the machine-builder procedure. Never perform resistance or continuity measurements on an energized circuit.
5. Inspect the Main Magnetic Contactor and Control Circuit
The main magnetic contactor, often identified as the MCC in service documentation, must close all power poles reliably. One defective pole can remove a phase even when the contactor appears to pull in normally.
Inspect and test:
- Whether the contactor closes fully and without chatter
- Condition of all main contacts and terminals
- Evidence of burning, pitting, overheating, or unequal contact wear
- Contactor coil voltage when energization is commanded
- Coil, auxiliary contact, and interlock operation
- Loose control wiring or intermittent control voltage
- Mechanical binding or a damaged contactor mechanism
- Voltage on both sides of every contactor pole under the authorized test procedure
Do not diagnose the contactor only by sound. A unit can make a normal closing sound while one main pole remains open or develops excessive resistance.
If the contactor or its contacts are defective, replace it with the exact approved specification. Do not file, bridge, or bypass power contacts as a permanent repair.
6. Check Fuses and Protective Devices Correctly
An open fuse is a common source of phase loss. Inspect all phases rather than only the fuse that appears damaged.
Confirm:
- The correct fuse type and rating are installed
- Each fuse has electrical continuity when safely isolated
- Fuse holders grip correctly and are not heat-damaged
- No fuse terminal is loose or discolored
- The associated circuit does not have a short circuit or ground fault
- All replaced fuses match the machine specification
The SP9004 message shown in the supplied image includes “open phase/fuse blown,” making the fuse path especially relevant. However, a blown fuse is a result as well as a symptom. If a replacement fuse opens again, stop and investigate the underlying fault instead of continuing to replace fuses.
7. Check Supply Stability, Phase Balance, and Frequency
The technician-supplied notes identify abnormal frequency, missing phase, and voltage imbalance as possible input-power abnormalities. These checks are especially useful when the alarm is intermittent or occurs only during production.
Investigate whether:
- Facility voltage fluctuates during operation of other large equipment
- One phase drops when the machine or another machine starts
- The machine transformer has a loose tap or internal problem
- A generator, converter, or facility source provides incorrect frequency
- Phase imbalance increases under load
- A poor upstream joint heats and opens intermittently
- The alarm follows a facility outage, electrical modification, or transformer change
Use a recording power-quality instrument when a brief event cannot be captured with a standard meter. Compare results with the input specification for the exact FANUC power-supply model and the machine builder's requirements.
Do not assume that every voltage variation is SV0607. FANUC uses separate alarm paths for DC-link undervoltage, control-power undervoltage, and other converter conditions. Diagnose the code actually displayed.
8. Evaluate the Common Power-Supply Module
If all three input phases reach the module correctly, voltage and frequency remain within specification, terminals and cables are sound, fuses are intact, and the contactor operates normally, the open-phase detection circuit inside the common power supply may be defective.
Before replacing the module, confirm the measurements at the precise points required by the applicable FANUC manual. A measurement made only at the facility disconnect can miss a fault inside the machine's wiring or contactor circuit.
If external power and connections are conclusively normal but SV0607 and alarm E remain, arrange professional testing or replace the common power-supply module according to the machine-builder procedure.
Before selecting a replacement, verify:
- Complete FANUC part number and every suffix
- αiPS or αiPSR series
- Input-voltage class and rated capacity
- Compatibility with all connected servo and spindle amplifiers
- Connector arrangement and cabinet installation
- Hardware and software requirements of the machine
If a replacement power-supply module is required, browse FANUC servo, spindle, and power drives or send the complete model to REACO CNC for a compatibility check.
9. Retest the Machine
After correcting the facility supply, fuse, breaker, terminal, cable, contactor, control circuit, transformer, or power-supply fault, restore the machine according to the approved procedure.
Confirm that:
- SV0607 and power-supply alarm E no longer appear
- Related SP9004 or SSPA:04 alarms are cleared
- All three input phases remain present when the main contactor closes
- Voltage remains stable and balanced during machine operation
- Terminals, fuses, and contactor poles show no abnormal heating or odor
- Servo axes and spindles start normally
- No DC-link, undervoltage, overcurrent, or communication alarm appears
- The machine completes the required production test cycle
If a different alarm appears, record the new number and diagnose it independently. Do not continue treating every subsequent converter alarm as SV0607.
Difference Between SV0607 and SP9004
SV0607 and SP9004 can appear together because both report the common converter input-power condition through different CNC alarm groups.
| Alarm | Associated display | Meaning |
|---|---|---|
| SV0607 | E on the applicable αiPS/αiPSR | Open phase in the converter main power supply, reported through the servo alarm group |
| SP9004 | 04 on the spindle amplifier and E on the power supply | Open phase in the converter main power supply, reported through the spindle alarm group |
When several servo axes show SV0607 and several spindles show SP9004 simultaneously, diagnose the shared common power input before suspecting individual axis or spindle hardware.
Difference Between SV0607 and Related FANUC Power Alarms
| CNC alarm | Typical display | Main condition | Primary diagnostic area |
|---|---|---|---|
| SV0604 | P | Communication error between amplifiers | CXA2A/CXA2B communication connectors, cable, and amplifier compatibility |
| SV0606 | A | Converter radiator cooling fan stopped | Common power-supply cooling fan and monitoring circuit |
| SV0607 | E | Converter main power open phase | Three-phase input voltage, connections, fuses, and contactor |
| SP9004 | 04 / E | Converter input open phase reported by the spindle system | Same common input-power path as SV0607 |
| SP9010 | 10 | Low power-supply input voltage | Input voltage magnitude rather than a confirmed missing phase |
| SP9051 | 51 / 4 | Converter DC-link undervoltage | DC-link voltage, input dips, sequence, and supply specification |
Always record both the CNC alarm and the character shown on the affected module. Similar power symptoms can lead to different repair procedures.
FANUC SV0607 Diagnostic Table
| Finding | Interpretation | Recommended action |
|---|---|---|
| CNC shows SV0607 and power supply shows E | Converter detected an input open phase | Measure all three input phases and inspect the power path |
| SV0607 appears on several axes simultaneously | A shared converter or incoming-supply fault is likely | Begin at the common power-supply input, not individual servo amplifiers |
| SV0607 and SP9004 appear together | Servo and spindle systems are reporting the same common power fault | Check shared fuses, contactor, terminals, and input voltage |
| One phase is absent at the machine incoming terminals | Facility supply, disconnect, or transformer fault | Correct the upstream source before testing the drives |
| All phases enter the machine but one is absent after a fuse | Fuse or holder is open or damaged | Correct the cause and install the specified fuse |
| Voltage is lost across one contactor pole | Contactor pole is not closing or has excessive resistance | Replace the approved contactor and inspect its control circuit |
| Alarm changes when a cable or terminal is moved | Intermittent conductor or loose connection is likely | Isolate power, repair the termination or replace the cable |
| Voltage is normal with no load but collapses during operation | High-resistance connection or weak supply may be present | Test the circuit under the authorized load condition |
| All three phases and connections are correct but alarm E remains | Internal open-phase detection circuit may be abnormal | Professionally test or replace the common power-supply module |
Recommended Troubleshooting Order
- Confirm SV0607 on the CNC and E on the applicable common power supply.
- Record all simultaneous servo and spindle alarms before switching off the machine.
- Record the complete power-supply model, input rating, and machine electrical configuration.
- Isolate power, observe the DC-link discharge time, and verify a safe condition.
- Inspect facility input, disconnect, breaker, fuses, transformer, contactor, terminals, and power cables.
- Have qualified personnel measure all phase-to-phase voltages at the approved test points.
- Trace any missing phase from the source toward the converter until the open point is identified.
- If all phases are present, inspect terminal torque, cable condition, fuse holders, and each contactor pole.
- Check voltage stability, phase balance, and frequency under the permitted operating test.
- Correct the external supply or connection fault and retest.
- If the input remains fully correct but alarm E persists, professionally test or replace the common power supply.
- Diagnose any new alarm separately.
Technical References
- FANUC AC Servo Motor αis/αi Series, AC Spindle Motor αi Series, Servo Amplifier αi Series Maintenance Manual, B-65285EN/04, Alarm Code E (αiPS and αiPSR)
- FANUC AC Servo Motor αis/αi Series, AC Spindle Motor αi Series, Servo Amplifier αi Series Maintenance Manual, B-65285EN/04, SV0607 and SP9004 alarm tables
- The applicable FANUC connection and maintenance manual for the exact common power-supply model and machine
Always use the manual edition that applies to the exact CNC, power-supply module, amplifier series, input-voltage class, and machine.
Need Help With FANUC SV0607?
REACO CNC provides independent testing, repair, compatibility checking, and replacement support for FANUC common power supplies, servo amplifiers, spindle amplifiers, and CNC systems. Send us the CNC alarm screen, every module display, complete power-supply model and suffix, machine input voltage, and details of when the alarm occurs.
Visit the FANUC Technical Support Center for more FANUC alarm guides, or contact REACO CNC for assistance.
Reference Source: Beijing FANUC. This article is based on FANUC technical documentation. The exact electrical checks and replacement procedure depend on the installed power-supply module and machine.
