Quick update.

Got the main panel on the wall and wired up all the stepper motors. I have changed over from series to parallel connections (on the X1,X2,&Y motors) to take advantage of the higher current available from the new drivers. I decided to solder and heat shrink the cables at the stepper motor end and dispense with the choc-block. One less terminal to come loose. Here it is before the final large heat shrink was placed over the cables:
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At the other end I re-did the connnectors including new earth cables to the outer screen. It all looked rather neat and tidy. Panel on wall (box sides and front to follow):
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(note stepper motors are un-plugged in photo)

Here is the loom I made up to join the BOB to the steppers:
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I then spent (wasted!) many hours this weekend trying to get the breakout board to talk to the stepper drivers. I checked the output from the direction pins and got around 4V or 0V depending upon direction. I wondered if this was a bit low so unplugged the USB lead and found a 5V source in the PC and made up a cable to connect to the 5V and GND pins instead. Got 5V output this time on the direction pins, but still no stepper movement.

I checked and double checked all the wiring, tried common anode and common cathode connections but still nothing. Checked all the Mach3 settings and they were all correct. Tried various things but to no avail. Borrowed an oscilloscope tonight and connected to the BOB pins. Direction still gave 5V or 0V but no pulse-train out of the step pins.

This was the BOB I was using - it was about £8 from ebay:
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In frustration I wired up the one which came free with the drivers:
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5V and GND from the PC, then pins 2 & 3 for step and direction and got a pulse-train! Plugged the driver back in one axis and the stepper moved ! So this will have to do to get it moving again with the new steppers. From that quick test it sounds much better than my all-in-one board if that is anything to go by.

I need to make up some proper looms for the bits I lashed up to get the new board working, but that should be straightforward.

The new board is very simple with no relays, speed control etc. so once I'm running I'll be looking into better boards with more features. There are a couple on my list such as the PMDX126, but not rushing into things.