Introduction

This guide explains how to troubleshoot a VFD / Spindle issue and determine whether the fault is within MASSO or the VFD.

The video at the bottom of this page walks through the procedure step by step. You can follow the written instructions below at the same time.

If the issue is identified as the VFD or spindle, contact your VFD or spindle supplier for further troubleshooting.

A spindle needs two things to operate:

• Speed – controlled by the voltage on Spindle Control Pin 1

• Direction – controlled by the Clockwise / Counter Clockwise signals on:

  • Pins 4 & 5 (CW)

  • Pins 6 & 7 (CCW)

   

Test Equipment

• Digital multimeter

Check Output Logic

Before testing, ensure the Spindle CW and Spindle CCW outputs are not inverted.

On the F1 screen, both outputs must show No in the Invert column.

If either shows Yes, select the output and press the spacebar to change it to No.

Testing the Speed Control

On the F2 screen, enter a spindle speed equal to 50% of the maximum spindle speed and press Spindle CW.

• Example:

  • Maximum speed = 24,000 RPM

  • Test speed = 12,000 RPM

Measure the voltage between:

• Spindle Control Pin 1, and

• Any black (GND) terminal on MASSO

You should see approximately 5 V (it may not be exactly 5 V).

• If you see ~5 V, the speed control output is working correctly. Proceed to direction testing.

If the voltage is low:

• Unplug the Spindle Control connector from MASSO and test again.

  • If the voltage is now correct, the VFD or its wiring is loading the signal.

    • Check wiring and consult your VFD supplier.

If the voltage is still low:

• Check spindle settings:

  • VFD selected

  • 10 V spindle speed setting is double the test speed

   

• If 5 V cannot be achieved, the spindle output may be damaged.

Contact MASSO Support and include a screenshot of the F2 screen showing the test in progress.

Testing Direction – Clockwise (Pins 4 & 5)

Step 1 – Spindle Stopped

1. Press Spindle Stop.

2. Measure voltage between:

   • Black probe on Pin 4

   • Red probe on Pin 5

You should see a voltage supplied by the VFD (commonly 24 V).

• If the reading is negative, the pins are reversed.

• If no voltage or a low voltage is present:

  • Confirm Spindle Stop is yellow on the F2 screen.

  • Unplug the spindle connector and measure again at the plug.

    • If still low - VFD or wiring fault

    • If correct - optocoupler fault

Refer to:

• How to replace optocouplers on MASSO G3 & MASSO Touch

Step 2 – Clockwise Active

1. Enter 50% spindle speed.

2. Press Spindle CW.

3. Measure voltage between Pins 4 & 5.

The voltage should drop to 0.6 V or less.

• If it does, the CW signal is correct and the issue is with the VFD.

• If it drops but stays above ~0.6 V (e.g. 24 V ? 5 V):

  • Check wiring for high resistance.

• If it does not drop:

  • The optocoupler is faulty and must be replaced.

If the issue remains after replacement, contact MASSO Support.

Testing Direction – Counter Clockwise (Pins 6 & 7)

The CCW test is identical to CW testing but uses Pins 6 & 7.

Step 1 – Spindle Stopped

• Measure voltage between:

  • Black probe on Pin 6

  • Red probe on Pin 7

• Expect VFD voltage (commonly 24 V)

If voltage is incorrect:

• Test with the spindle connector unplugged.

• Determine whether the fault is the VFD, wiring, or optocoupler.

Step 2 – Counter Clockwise Active

1. Enter 50% spindle speed.

2. Press Spindle CCW.

3. Measure voltage between Pins 6 & 7.

Expected result: 0.6 V or less

• If correct ? CCW signal is working, VFD issue

• If voltage does not drop sufficiently ? wiring or optocoupler issue

• If voltage does not change ? optocoupler is faulty

Replace the optocoupler as required and retest.

Video Guide

A step-by-step video guide is provided below to visually walk through this procedure.