231-4290

Check Drive Amplifier Status Display

Inspect the LED indicators or display on the servo amplifier for the affected axis. Most Heidenhain-compatible drives (such as Rexroth IndraDrive, Siemens, etc.) will show a specific fault code. Document the error code displayed on the drive.

Do not attempt to clear drive faults without identifying the root cause - repeated faults can cause permanent drive damage.

Verify Drive Power Supply

Measure the DC bus voltage at the drive amplifier power terminals. Verify it is within specification (typically 565-590V DC for 3-phase input). Check for DC bus ripple or instability that could cause undervoltage/overvoltage trips.

High voltage present - use appropriate PPE and test equipment rated for DC bus voltage measurements.

Check Motor Temperature and Connections

Verify the motor temperature sensor feedback (KTY84 or similar) is correctly connected to the drive. Check motor temperature in the drive's diagnostic menu. Loose motor power connections can cause overcurrent faults.

On TNC systems with EnDat encoders, check that the encoder temperature monitoring is also functional - encoder overtemperature can cause drive shutdowns.

Reset Drive and Monitor

After resolving any identified fault condition, reset the drive amplifier using its reset input or control panel. From the TNC, acknowledge the alarm and attempt a reference run. Monitor whether the fault recurs immediately or during motion.

Use MOD/System Configuration/Axis Status to monitor real-time current demand during test moves - recurring faults at consistent current levels indicate mechanical binding or motor issues.

Measure 24V at Drive Terminals

Using a multimeter, measure the 24V DC supply at the drive amplifier control terminals (typically labeled X101, X102, or similar). Verify voltage is between 22-26V DC under load. Check both supply and ground connections.

Measure with the drive enabled - voltage drop under load indicates undersized supply or poor connections.

Check 24V Supply Fuses and Breakers

Locate the 24V DC power supply in the electrical cabinet and verify all output fuses and circuit breakers. Check the fuse specifically feeding the axis drive amplifiers. Verify supply load current is within rated capacity.

A blown 24V fuse may indicate a short circuit condition - identify and repair the short before replacing the fuse.

Inspect TNC X101/X102 Power Connections

Check the 24V supply connections at the TNC's X101 and X102 terminals (or equivalent depending on TNC model). Verify voltage at these terminals and check for oxidation, loose screw terminals, or burned connections.

The TNC itself monitors 24V supply quality - check System Monitoring/Power Supply Status for any logged undervoltage events.

Test Enable Signal Chain

Access PLC/PLC Status on the TNC and monitor the axis enable signals (typically M000 through M00X markers). Verify that the enable chain including EMERGENCY STOP, safety relays, and axis enable outputs are all active when attempting to enable the axis.

Use the TNC's built-in PLC trace function (MOD/PLC/Trace) to capture the exact sequence of signal changes when the RDY signal is lost.

Inspect TNC Axis Connector

Power down the system and inspect the X3X or X4X connector (depending on axis assignment) at the TNC. Check for bent pins, corrosion, or contamination. The RDY signal typically uses dedicated pins in the digital I/O section of the connector. Verify connector locking mechanism is secure.

Power must be completely off before disconnecting TNC axis connectors - label all connectors before removal.