FANUC SRVO-206 Deadman Switch Alarm: Causes and Troubleshooting

When a FANUC robot displays SRVO-206 Deadman Switch (SVEMG abnormal), the controller has detected an abnormal condition involving the Teach Pendant enabling device and the emergency stop circuit.

The Deadman Switch is a safety device that allows an operator to enable robot motion during manual operation. The controller monitors its status as part of the robot's safety system.

According to FANUC maintenance documentation, SRVO-206 occurs when the Teach Pendant is enabled and the Deadman Switch is released or pressed strongly, but the emergency stop line does not disconnect as expected.

This is different from a normal Deadman Switch Released alarm.

The problem may involve the Teach Pendant assembly, its internal Deadman Switch circuit, the Teach Pendant cable, or safety-related hardware inside the controller.

This guide explains what SRVO-206 means, how to distinguish it from other Deadman Switch alarms, and which components should be investigated before ordering replacement parts.

1. What Does FANUC SRVO-206 Mean?

SRVO-206 – Deadman Switch (SVEMG abnormal)

SRVO-206 indicates that the controller has detected an abnormal relationship between the Teach Pendant Deadman Switch and the emergency stop circuit.

FANUC maintenance documentation describes the condition as follows:

When the Teach Pendant is enabled, the Deadman Switch is released or pressed strongly, but the emergency stop line is not disconnected.

In other words, the controller detects an abnormal response from the safety circuit when the Deadman Switch changes position.

The alarm does not simply mean that the operator released the Deadman Switch.

It indicates that the expected emergency stop response was not detected.

What Is a FANUC Deadman Switch?

The Deadman Switch is an enabling device located on the rear of the Teach Pendant.

It allows an operator to enable manual robot operation while maintaining control of the safety enabling function.

On applicable FANUC Teach Pendants, the switch uses a three-position operating principle:

Switch Position	General Function
Released	Enabling signal is not maintained
Middle position	Enables the required manual operation condition
Fully pressed	Enabling condition is released for safety

The exact switch design and operating procedure depend on the Teach Pendant model.

The Deadman Switch is a safety-related component. It must function correctly before the robot can be returned to normal operation.

2. SRVO-206 vs. SRVO-003: What Is the Difference?

This distinction is important because both alarms involve the Teach Pendant Deadman Switch.

However, they describe different conditions.

Alarm Code	Alarm Description	Main Meaning
SRVO-003	Deadman Switch Released	The Deadman enabling condition has been released
SRVO-206	Deadman Switch (SVEMG abnormal)	The Deadman Switch was released or pressed strongly, but the emergency stop line did not disconnect as expected

SRVO-003 is associated with the normal enabling-device release condition.

SRVO-206 indicates an abnormal safety circuit response.

Do not treat these alarms as interchangeable or assume they require the same repair.

If both alarms appear in the alarm history, review the sequence and the applicable controller maintenance documentation before selecting a replacement component.

3. Common Causes of FANUC SRVO-206

Several components may be involved in an SRVO-206 alarm.

FANUC maintenance manuals list the Teach Pendant, Teach Pendant cable, main board, emergency stop board, and 6-axis servo amplifier among the components to investigate, depending on controller configuration.

3.1 Teach Pendant Deadman Switch Failure

The Deadman Switch is the first component to investigate.

Possible problems include:

• Worn or damaged switch mechanism.

• Abnormal internal switch contacts.

• Failure to detect the correct switch position.

• Internal electrical connection problems.

• Damage caused by repeated operation or impact.

If the switch cannot provide the expected safety signal, the controller may detect an abnormal Deadman condition.

However, SRVO-206 does not automatically prove that the switch itself is defective.

The complete Teach Pendant assembly may need to be inspected or replaced according to the applicable FANUC procedure.

3.2 Teach Pendant Internal Circuit Fault

The Deadman Switch is connected to the Teach Pendant's internal electrical system.

A fault inside the pendant may prevent the expected emergency stop signal from being transmitted correctly.

Potential areas include:

• Internal switch wiring.

• Electrical contacts.

• Internal connectors.

• Safety-related circuit components.

If the physical switch appears normal but SRVO-206 remains active, the internal Teach Pendant circuitry should be investigated.

3.3 Damaged Teach Pendant Cable

The Teach Pendant cable connects the pendant to the robot controller.

A damaged cable or faulty connection may interrupt or affect the signals associated with the Deadman Switch and emergency stop circuit.

Possible signs include:

• Visible cable damage.

• Damaged connector housing.

• Intermittent pendant operation.

• Abnormal behavior that changes with cable position.

• Recurring safety-related alarms.

FANUC maintenance documentation specifically lists checking the Teach Pendant cable as an action for SRVO-206.

If the cable is confirmed defective, replace it with the correct compatible cable.

Do not assume that every intermittent pendant problem is caused by the cable. The internal switch and controller-side safety circuit may also require inspection.

3.4 Main Board Fault

If the Teach Pendant and its cable are confirmed normal, the controller's main board may require further investigation.

The main board participates in processing and monitoring signals associated with the robot control system.

For applicable R-30iB controller configurations, FANUC maintenance documentation lists main board replacement as a later corrective action for SRVO-206.

Important: Certain R-30iB Mate/Mate Plus maintenance procedures require a complete controller backup before proceeding with main board replacement.

Always follow the backup and replacement instructions in the correct maintenance manual.

3.5 Emergency Stop Board Fault

The emergency stop board, also called the E-stop unit in some FANUC documentation, is another component involved in the safety circuit.

If the Teach Pendant and cable are normal but the emergency stop line does not respond correctly, the emergency stop board may need further diagnosis.

A faulty board may prevent the expected safety circuit response.

The exact board configuration and replacement procedure vary by controller cabinet.

3.6 Servo Amplifier or Other Controller Hardware

Some FANUC maintenance procedures also list the 6-axis servo amplifier as a later component to investigate for SRVO-206.

This does not mean that the servo amplifier is the most likely cause.

It is included in certain controller-specific troubleshooting sequences after the Teach Pendant, cable, and other safety-related components have been checked.

The applicable controller manual should determine whether this component is relevant to the installed system.

4. How to Troubleshoot FANUC SRVO-206

A systematic diagnosis helps identify the actual failure without replacing unnecessary components.

Step 1: Confirm the Exact Alarm

Open the FANUC alarm screen and confirm:

SRVO-206 – Deadman Switch (SVEMG abnormal)

Record:

• Complete alarm description.

• Controller model.

• Teach Pendant model.

• Alarm occurrence time.

• Other alarms appearing at the same time.

Also review the alarm history for related Deadman Switch or emergency stop alarms.

Do not diagnose SRVO-206 as a simple SRVO-003 condition.

Step 2: Inspect the Teach Pendant Deadman Switch

Visually inspect the Deadman Switch on the rear of the Teach Pendant.

Check for:

• Cracks or physical damage.

• Abnormal looseness.

• Sticking or restricted movement.

• Signs of impact or previous repair.

• Abnormal switch operation.

Do not repeatedly squeeze or manipulate a suspected faulty safety switch in an attempt to clear the alarm.

If the switch is damaged or its operation is abnormal, arrange inspection by qualified maintenance personnel.

Step 3: Check the Teach Pendant Cable

Inspect the external Teach Pendant cable and connector.

Look for:

• Cuts or damaged insulation.

• Crushed or sharply bent sections.

• Connector damage.

• Loose connections.

• Evidence of previous cable repair.

If the cable is suspected to be defective, follow the FANUC maintenance procedure to verify the condition.

Replace the cable only with a compatible part for the specific Teach Pendant and controller configuration.

Step 4: Inspect the Teach Pendant Assembly

If the Deadman Switch and external cable appear normal, the Teach Pendant itself may be defective.

For applicable FANUC R-30iB maintenance procedures, replacing the Teach Pendant is listed as the first corrective action for SRVO-206.

If the replacement procedure is followed, confirm the correct pendant model and hardware configuration before installation.

Do not assume that two pendants with similar appearance are interchangeable.

Step 5: Investigate Controller-Side Safety Hardware

If the Teach Pendant and cable have been checked or replaced but SRVO-206 remains, controller-side components may need further diagnosis.

Depending on the controller generation, the maintenance procedure may include:

• Main board.

• Emergency stop board.

• NTED signal wiring, when used.

• 6-axis servo amplifier.

These checks should be performed by qualified technicians using the correct controller maintenance manual.

For example, applicable R-30iB maintenance documentation includes checking the NTED signal wiring connected to the emergency stop board when that signal is used.

Step 6: Complete the Required Repair and Safety Verification

After repairing or replacing the identified component:

• Follow the approved FANUC maintenance procedure.

• Confirm that the replacement component is compatible.

• Check whether SRVO-206 has cleared.

• Verify that the emergency stop and enabling functions operate correctly.

• Complete the required safety validation before returning the robot to production.

Do not resume robot operation until the safety-related fault has been resolved and the required checks have been completed.

5. SRVO-206 Troubleshooting: Which Component Should You Replace?

The following table summarizes the main components identified in applicable FANUC maintenance procedures.

Component	Why It May Be Involved	When to Investigate
Teach Pendant	Deadman Switch or internal circuit fault	First component to investigate
Teach Pendant Cable	Signal interruption or cable damage	When the pendant connection is suspected
Main Board	Controller-side signal processing fault	After pendant and cable checks
Emergency Stop Board	Abnormal emergency stop circuit response	When the safety circuit remains abnormal
6-Axis Servo Amplifier	Controller-specific hardware fault	When listed by the applicable maintenance procedure

The order and scope of these checks vary across FANUC controller generations.

For example:

• R-30iB maintenance documentation lists the Teach Pendant, cable, emergency stop board, and 6-axis servo amplifier, with an additional NTED wiring check when applicable.

• R-30iB Mate/Mate Plus documentation also includes the main board, and requires a complete controller backup before the main board replacement step.

• R-30iA Mate documentation uses a different sequence and lists the main board, servo amplifier, and E-stop unit as later corrective actions.

Always use the maintenance manual corresponding to the installed controller.

6. How to Identify the Correct FANUC Deadman Switch or Teach Pendant Replacement

If the Teach Pendant is confirmed defective, the correct replacement must be identified before ordering.

FANUC Teach Pendants vary by controller generation and hardware configuration.

A similar-looking pendant may have a different connector, internal circuit, or safety switch arrangement.

6.1 Complete Teach Pendant Part Number

Record the full part number from the original Teach Pendant identification label.

Include all suffixes and revision information.

This is one of the most important details for confirming compatibility.

6.2 Controller Model

Identify the installed FANUC controller:

• R-30iA

• R-30iA Mate

• R-30iB

• R-30iB Mate

• R-30iB Plus

• Other applicable FANUC controller generations

Controller information helps establish the correct pendant configuration.

6.3 Deadman Switch Configuration

If sourcing the individual Deadman Switch rather than the complete Teach Pendant, confirm:

• Original switch part number.

• Mechanical mounting.

• Electrical connector.

• Switch configuration.

• Compatibility with the pendant model.

Do not assume that an individual switch can be replaced independently on every Teach Pendant.

6.4 Photos and Identification Labels

If the original part number is unavailable, provide:

• Front view of the Teach Pendant.

• Rear view showing the Deadman Switch.

• Rear identification label.

• Cable connector.

• Photos of any damaged components.

These details help verify the correct replacement.

7. Replace the Deadman Switch or the Complete Teach Pendant?

The correct replacement depends on the actual pendant design and confirmed fault.

Replacement Option	When to Consider It
Individual Deadman Switch	The switch is separately replaceable and its failure is confirmed
Complete Teach Pendant	The internal safety circuit or pendant assembly is defective, or the applicable procedure requires pendant replacement
Teach Pendant Cable	Cable damage or signal interruption is confirmed
Main Board	Controller-side fault is confirmed through the applicable diagnostic procedure
Emergency Stop Board	Emergency stop circuit fault is confirmed
6-Axis Servo Amplifier	The controller-specific diagnostic procedure identifies it as defective

For many SRVO-206 cases, the Teach Pendant and its cable should be investigated before moving to controller-side components.

Replacing the complete Teach Pendant may be appropriate when its internal Deadman or safety circuitry is defective.

However, do not replace the entire pendant based only on the alarm code.

8. Important Safety Considerations

The Deadman Switch is a safety enabling device. It must never be treated as an ordinary operating button.

When troubleshooting SRVO-206:

• Never bypass or short-circuit the Deadman Switch.

• Never jumper the emergency stop circuit to clear the alarm.

• Never hold the switch in an improvised position to force robot operation.

• Do not operate the robot with a defective enabling device.

• Follow the applicable FANUC maintenance manual.

• Have qualified personnel perform controller-side electrical checks.

• Complete the required safety validation after repair.

The purpose of the Deadman Switch is to ensure that manual robot movement remains under the operator's control.

A fault in this circuit must be corrected, not bypassed.

9. Frequently Asked Questions

What does FANUC SRVO-206 mean?

SRVO-206 means Deadman Switch (SVEMG abnormal). The controller has detected that the Teach Pendant Deadman Switch was released or pressed strongly while the pendant was enabled, but the emergency stop line did not disconnect as expected.

Is SRVO-206 the same as SRVO-003?

No.

SRVO-003 is associated with the Deadman Switch Released condition. SRVO-206 indicates an abnormal response from the emergency stop circuit when the Deadman Switch changes position.

Does SRVO-206 mean the Deadman Switch is broken?

Not necessarily. The Teach Pendant is the first component identified in applicable FANUC troubleshooting procedures, but the Teach Pendant cable and controller-side safety hardware may also need investigation.

Can a damaged Teach Pendant cable cause SRVO-206?

Yes. FANUC maintenance documentation specifically lists checking the Teach Pendant cable and replacing it if defective.

Should I replace the complete Teach Pendant?

If the pendant's Deadman Switch or internal safety circuit is confirmed defective, replacing the complete Teach Pendant may be appropriate. The exact repair procedure depends on the pendant and controller generation.

Can I replace only the Deadman Switch?

This depends on the Teach Pendant design and whether the switch is separately replaceable. Verify the original part number and service documentation before ordering an individual switch.

Can I bypass the Deadman Switch to clear SRVO-206?

No. The Deadman Switch is part of the robot's safety system. Bypassing or short-circuiting it is not an acceptable repair method.

Source FANUC Deadman Switch and Teach Pendant Parts

If your FANUC robot displays SRVO-206, identifying whether the problem comes from the Deadman Switch, Teach Pendant, cable, or controller-side safety hardware is the first step toward a reliable repair.

InRobots supports sourcing FANUC Teach Pendant assemblies, Deadman Switch components, Teach Pendant cables, and other hard-to-find industrial robot spare parts.

To help identify the correct replacement, provide:

• FANUC controller model.

• Complete Teach Pendant model.

• Original Teach Pendant part number.

• Complete SRVO-206 alarm message.

• Photos of the Deadman Switch and identification label.

• Cable and connector photos, if available.

• Description of the troubleshooting already performed.

• Required quantity.

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You can also explore our Fanuc Teach Pendant Parts for related replacement components.