Troubleshooting non responsive machine- Mach3/Syil x4

[Doddy]

OP: Sorry, I might have ignored some interesting and relevant info that you posted. I *think* I'm right in my understanding that you've measured from the white wire (that I think you've decided (correctly) is ground/0V and pin 11 of the DB25 connector, and you're getting either 1V or 0V indicated depending on the state of the E-Stop?

If that is true, and I'm being cautious with what I think you're saying and my understanding. But if that is the case then there is something badly wrong on this breakout board. Can you measure the voltage (with reference to 0v/ground on the white wire) - the 5V supply voltage from the voltage regulator. You might find it easier picking this up on pins 2, 4 or 6 of any of the IDC connectors. There's many other places to pick it up off the board - you might be able to pick it off the "VCC" terminal on the Y Home sensor terminal block (I'm assuming that this is sourced from the on board 5 regulator).

Another question - are any (and if so, which) LEDs illuminated on the board?