OK,
Back on topic.....
The machine in question has blown 2 boards since new.
I had bought one new board back when they were releasing them, which also blew a couple of weeks later.
Both blew the same mosfet mentioned earlier by Julia, after both exhibiting the same runaway temp on startup without a print being initiated.
I sent the second blown board back to the distributor as Z had implemented the exchange thing and I'm waiting for a replacement.
In the meantime I managed to replace the mosfet on the first board that i had here, and it's been working normally until this morning.
Same thing....turn the machine on and the extruder temp begins heating right up without a print being initiated. Thank god I hadn't fitted a third board.
1. Checked the other 2 machines and nothing like that, the bed warms but the extruder stays cold (basics I know, just covering bases).
2. Plugged in a spare complete hot end in case thermocouple sensor was causing it, did exactly the same thing.
What next?
I've got ribbon cables here, but is that likely to be it? When the other machine did the same thing (I've got 2 broken with this same fault, and 2 that have never had a problem) I changed the ribbon cable but it didn't fix it.
It seems that the issue is about the board initiating the extruder heating sequence by itself without receiving the command via the display/switch to start a print....I think there's something else being missed here.
Marcin/Zortrax, I think there's something else going on here that's triggering this, and would really appreciate one of your techs putting a step by step of things to check for this issue.
I do know of one other case in Brazil with the exact same fault, and he has bought a new mosfet as well, but my guess is that his problem will come back as well and we are only curing the symptom not the fault.
I'll start with the service center, but this is really getting to be a pain in the arse.
I just started catching up with orders with 3 machines available and here I am again with 2.