OmniTurn G3 CNC: Spindle Starts in Only One Direction
Legacy Inverter Spindle Drive (TB1)

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The instructions on this page assume you have performed initial tests here, and found that the spindle will start in one direction (M03 or M04), but not the other.

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Open the Spindle Drive Cabinet

• Set the CNC control off, and turn the spindle drive cabinet switch to OFF.
• Open the cabinet door, then use a small wrench or pliers to turn the 1/4" shaft to set the spindle drive power on.
• Set the CNC power on and turn on servos.

Measure Voltages on TB1

TB1 is the long terminal strip that runs down the left side of the electrical panel. Terminal 1 is the top terminal on the strip. (For reference, here is PDF of spindle cabinet components)

• In MDI mode, issue M05. This is to insure that neither M03 or M04 is active for first test.


• If M03 is OK, but not M04:
  Measure TB1-8 to TB1-7:Meter between TB1-8 and TB1-7 with M05 Should be 12 volts DC. This is the "M04 enable" voltage from the motion control card (MC2).
• If it's 12 volts DC, issue M04 in MDI mode:
• Measure TB1-8 to TB1-7 again:Meter between TB1-8 and TB1-7 with M04 should measure about 1 - 2 volts DC with M04 engaged. If you still measure 12 volts DC, you can try replacing the output driver U17 on the MC2 board, or you can order replacement MC2 board.
• If it's not 12 volts DC, the problem may be the 37-pin ribbon cable between MC2 and Connect Card, or pin 4 of MISC cable. Unplug and replug the 37-pin ribbon cable; check again. If not 12 volts DC, "ring-out" the MISC cable, pin-to-pin, but especially pin 4. If the cable is good, check again: if still no 12 volts between TB1-8 to TB1-7, email service@omniturn.com for help.

• If M04 is OK, but not M03:
  Measure TB1-8 to TB1-5:Meter between TB1-8 and TB1-5 with M05 Should be 12 volts DC. This is the "M03 enable" voltage from the motion control card (MC2).
• If it's 12 volts DC, issue M03 in MDI mode:
• Measure TB1-8 to TB1-5 again:Meter between TB1-8 and TB1-7 with M03 should measure about 1 - 2 volts DC with M03 engaged. If you still measure 12 volts DC, you can try replacing the output driver U17 on the MC2 board, or you can order replacement MC2 board.
• If it's not 12 volts DC, the problem may be the 37-pin ribbon cable between MC2 and Connect Card, or pin 6 of MISC cable. Unplug and replug the 37-pin ribbon cable; check again. If not 12 volts DC, "ring-out" the MISC cable, pin-to-pin, but especially pin 6. If the cable is good, check again: if still no 12 volts between TB1-8 to TB1-5, email service@omniturn.com for help.