230-0496

Access encoder parameters

Navigate to MOD > Machine Parameters > MP720 series for the affected axis (%1).

Always backup machine parameters before making changes

Verify encoder type setting

Check MP720 (encoder type) matches physical encoder: 0=incremental, 1=absolute, 2=EnDat, 3=SSI, 4=Fanuc serial.

Incorrect encoder type can damage encoder electronics

Validate encoder resolution

Confirm MP721 (lines per revolution) matches encoder nameplate specifications exactly.

Test configuration

Reset alarm and perform slow manual axis movement to verify encoder feedback is valid.

Power down and inspect connections

Check encoder cable connections at both motor and TNC/drive ends for corrosion, bent pins, or loose connections.

Always power down before disconnecting encoder cables

Measure cable continuity

Use multimeter to check continuity of all encoder cable conductors, including shield ground connection.

Check signal quality

With oscilloscope, verify encoder A/B channel signals are clean square waves with proper amplitude (typically 5V TTL or differential).

Look for signal reflections or noise that indicate cable impedance issues

Inspect for mechanical damage

Examine entire cable length for cuts, pinch points, or areas where cable may have been damaged by machine movement.

Check encoder power supply

Verify encoder receives correct supply voltage (typically +5VDC or +24VDC) at encoder connector using multimeter.

Monitor encoder current draw

Measure encoder current consumption - excessive current indicates internal short circuit, no current indicates open circuit.

Test encoder output signals

Manually rotate axis while monitoring A/B channel outputs with oscilloscope - should see clean quadrature signals.

Count pulses per revolution to verify encoder resolution matches MP721 parameter

Replace encoder if faulty

If no valid signals present with good power supply, replace encoder and recalibrate axis reference point.

Check drive status LEDs

Examine servo drive front panel LEDs for encoder fault indicators or error codes specific to encoder input.

Verify drive encoder parameters

Access drive internal parameters via TNC diagnostic screens to confirm encoder interface settings match MP720 configuration.

Test with known good encoder

Temporarily connect a verified working encoder to isolate whether issue is drive-side or encoder-side.

Ensure encoder types match before connecting to prevent damage

Replace drive module

If encoder input circuitry is confirmed faulty, replace servo drive amplifier and restore parameters from backup.