U17 on MC2 card
Failure to actuate M03, M04, M08, M12, M13, or M25 could be caused by bad output driver U17 on MC2 board. If troubleshooting all switches, cables, connectors, etc, does not fix the problem, U17 may be the culprit.
After troubleshooting all switches, cables, and connectors associated with the M‑function that doesn't engage, you can verify that U17 may be bad by checking voltages on terminal strip TB1 in the spindle cabinet.
To make these measurments, the spindle cabinet must be open, the CNC controlled powered up, and the servos must be on.
MDI mode will be used to issue the m‑function. For all measurements, the meter must read about 12 volts DC between the two terminals before the m‑function is issued. After the m‑function is issued the meter should read 1 - 2 volts DC. If the voltage does not drop to about 1 - 2 volts when m‑function is issued, replace U17.
M03: TB1-5 to TB1-8
M04: TB1-7 to TB1-8
M08: TB1-10 to TB1-8
M12: TB1-15 to TB1-8
M13: TB1-12 to TB1-8
M25: TB1-11 to TB1-8
If the voltage doesn't drop to 1 - 2 volts, the driver on the motion card (MC2) is the probably the culprit.
Replace U17 (ULN2803A; available at DigiKey.com).
U17 on MC2 card