231-8A20

Check DC Bus Voltage

Navigate to MOD > System Info > Drive Diagnosis and verify DC bus voltage readings are within specification (typically 540-750VDC for standard systems).

Compare readings across all axes - significant variations indicate power distribution issues.

Inspect Power Supply Unit

Check the main power supply unit LED indicators and measure output voltages. Verify 24VDC control voltage and main DC bus output.

Only qualified personnel should access high voltage areas. Follow lockout/tagout procedures.

Verify Input Power Quality

Measure incoming AC line voltage and check for voltage drops, phase imbalances, or harmonic distortion that could affect power supply performance.

Use a power quality analyzer to capture transient events that may not show on standard multimeters.

Check Power Supply Connections

Inspect all power connections from AC input through DC bus distribution, looking for loose connections, corrosion, or overheating signs.

Ensure proper PPE and follow electrical safety procedures when inspecting connections.

Access Power Monitoring Parameters

Navigate to MOD > Machine Parameters and check parameters 1410-1419 (Power Monitoring) for correct voltage thresholds and monitoring settings.

Document original parameter values before making any changes for easy restoration.

Verify Monitoring Thresholds

Check parameter 1410 (minimum DC bus voltage) and 1411 (powerfail delay time) are set correctly for your system specifications.

Incorrect threshold settings can cause nuisance alarms or fail to protect against actual power issues.

Test Power Monitoring Circuit

Use TNC diagnostic functions in MOD > Diagnosis > Power to test the power monitoring circuit response and compare with actual measured voltages.

Perform this test during different load conditions to verify consistent monitoring performance.

Check Control Board Connections

Inspect connections between power supply monitoring outputs and TNC control board inputs, particularly X101 connector pins related to power status.

Use contact cleaner on connector pins if oxidation is present, but ensure system is powered down first.

Check Individual Drive Status

Navigate to MOD > Diagnosis > Axis and check each axis drive for fault codes or status indicators showing internal drive problems.

Note which specific axis shows the fault - this helps isolate the problem to specific drive hardware.

Inspect Drive LED Indicators

Physically check each drive amplifier for LED fault indicators and compare with drive manual fault code definitions.

Do not attempt to reset drives until root cause is identified to prevent equipment damage.

Verify Drive Enable Signals

Check that drive enable signals from TNC to each amplifier are present and at correct voltage levels (typically 24VDC).

Use oscilloscope to check for signal integrity issues or noise that might prevent proper drive enabling.

Test Drive Power Connections

Verify DC bus connections to each drive amplifier are secure and measure voltage at drive input terminals.

High voltage present - use appropriate safety procedures and insulated tools.

Check Emergency Stop Status

Navigate to PLC > Status > Inputs and verify emergency stop input status (typically M5000-M5003 markers) shows all E-stops are released.

Check both physical E-stop buttons and any software-based emergency stops that may be active.

Verify Safety Relay Chain

Check safety relay contactor status and measure voltage across safety relay contacts to ensure proper operation of the safety circuit.

Never bypass safety circuits - identify and correct the root cause of safety system activation.

Test Power Enable Signal

Verify the power enable signal from safety system to drive power supply is present and at correct voltage level.

Use the TNC's built-in PLC program to trace the safety signal path through the logic.

Check Door/Guard Interlocks

Verify all safety door switches and guard interlocks are properly closed and providing correct feedback to the safety system.

Mechanical adjustment of door switches may be needed if doors have sagged over time.

Perform TNC Self-Diagnostics

Navigate to MOD > Diagnosis > System Test and run comprehensive hardware diagnostics to identify control board issues.

Save diagnostic results to file for technical support reference if board replacement is needed.

Check Control Voltages

Measure all control voltages (±15VDC, +5VDC, +24VDC) at the TNC control board to verify proper power supply to control circuits.

Static sensitive components - use proper ESD precautions when working near control boards.

Verify Interface Signals

Check signal integrity between TNC and drive interface connections, particularly power status feedback signals.

Compare signal levels with known good system documentation or contact Heidenhain support for specifications.

Document for Service Call

If control board failure is suspected, document all test results, parameter settings, and system configuration for service technician.

Create backup of TNC parameters and PLC program before service technician arrives to speed repair process.