Preliminary:

Some debugging tips:

If you seem to be loosing steps:

Are you running a DOS based program in a Windows DOS box (even under full screen mode)?

If so, try either booting off of a DOS floppy disk and then run your DOS CNC software, or if your Win software allows, press F8 at bootup and run from the "Command Prompt" mode. Then run the DOS CNC software. This way Windows does not use time slots that may interfere with your CNC program timing.

Check the voltage on the X DIR line. A logic 1 must be at .7 * VCC to be recognized at a 1 . Thus if you measure 5V on VCC then a logic 1 would be .7 * 5 = 3.5V for a logic 1. Some motherbaord parallel ports do not reach this voltage level. Almost all PCI add-in parallel port will. The minimum pulse width for the STEP signal is 1 uS (one microsecond). The DIR line must be stable at least 200 ns (nanosecond before the rising edge of the STEP signals, and remain stable for at least 200 ns after the rising esge of the STEP signal. A logic 0 voltage should be .9V or less. The easiest way to test this is with your voltage meter probing the X DIR line. Have software jog the X axis one direction, note the voltage, and jog the other direction, and again note the voltage.

What is your Vref set to?, what is your voltage set at?

The device can go into a thermal shutdown cycle when the chip is run at high voltages and high current. The PEAK allowable voltage the board may be subjected to is 35V. This includes Back EMF (electricity created by the stepper motor itself when decelerating). The maximum suggested running voltage is 30V. In some cases, when running with a voltage near 30V, the device can go into thermal shutdown even before the heatsinks get hot. In this situation, reduce the current by adjusting the Vref to a lower voltage. The maximum current (2.5A/phase) is achieved at a Vref of 3.60V. When running at this level over extended periods of time, the device can get hot. It is suggested that a cooling fan be used to blow air accross the heatsinks.

If your Vref is set too low, the motor will not be fully energized and produce the proper amount of torque.

What is your motor speed and acceleration set to?

If you try to run the motor too fast, or accelerate the motors too fast, they can loose step. Modify the acceleration and step rates in software.

If the motors "lock up" but do not turn

Are the STEP and DIR pins wired correctly?

Make sure that your STEP & DIR signals in software match with the board setting. i.e. DB25-pin 2 is STEPX, and DB25-pin 3 is DIRX

If the motors do not "lock up"

Are the ENA# pins on J1 pullel "LOW' (somewhere around .9V or less)

The ENA# lines can be controlled by digital logic from the parallel port, or external switches. If the ENA# feature is not used the lines can be directly tied to GND. This is the function of the ENA# connector.

Do you have motor voltage (and GND) applied to J9 correctly (minimum of 8V, typicall 24V, max running 30V, MAX peak 35V)?

The drive require a minimum voltage of 8V to supply onboard "charge pumps" used to drive internal transistors. Voltage less than 8V will not work.

Do you have voltage +5V logic voltage (and GND) applied J8 (VCC) correctly?

The board requires a logic voltage of at least 4.6V to be in an active state. Typical running voltage for VCC will be somewhere around 4.9V to 5.2V

What is the resistance in ohms betwenn A & A#, and B & B# (with NO stepper motors attached)?

The resistance should be around 10 megohms. If it's more like 10 ohms, then the chip is blown, and the board needs fixing.

If you get little "glitches" when running your spindle

Is your spindle properly connected to Earth Ground?

Some spindle mounts are painted, powdercoated,or hard anodized, and do not conduct. You may need to run a ground wire driectly to your spindle motor

If you get little "glitches" when turning on/off your spindle

Does your switch have a snubber in it?

Large voltages can be created when turning off a spindle motor. A snubber can help absorb those so they are not tranmitted to the power line

When contacting for help, please include the following information:

1) CPU speed

2) Operating system

3) CNC software

4) Motor VBB voltage

5) Vref setting Voltage

6) Motor amperage and voltage rating

7) Motor winding method (bipolar parallel, bipolar series, or bipolar half-winding)]

8) Voltage levels on DIR pin for logic 1 and logic 0