I did some more testing today and low and behold..... I hadn't wired up 2 critical wires inside the Hypertherm Plasma unit. That's an " ID 10 T " error (put the letters together and read them from a distance and you will see what I mean.)

I still, for some reason, can't get the THC to start up in Mach3 but the rest of it is working now. I cut out about 6 items today at a very slow feed rate so I could control the tip and stop it from burying itself and everything was as it should be and the voltage sensing was working and I could control the height by varying the tip volts etc but the LED on the Mach3 screen still won't light up. Frustrating stuff this.
soon, very soon it will be up and running and then I can start cutting s**t up and hopefully sell some and get some money back.
Did I mention this is fun.........
After 1.5 years with about 3 months of problem solving it all gets a bit weary after a while. Sometimes I think it would have been easier to hook up a capacitive sensor to the thing for 1/3 the price but I am told this is the way to do it so you can cut almost anything with ease. I hope they're right.
When I get it up and running I think I will take a few pictures and draw up a connection diagram for anyone that will be using the (now obsolete) MP1000C digital torch height controller from CandCNC. Tom Caudle is a bit of a legend at designing these things and he is second to none for his reply times on the forums and at the "zone". It will be good to give back some feedback for others as without this the forums would be useless and I would still be rolling around in the grease and muck for the rest of my life. Now I will have something to fall back on. :-)
I will get the pictures up as soon as is practicable.
Rich.