Hi Tony, I have tried another probe with the same result (they are only cheap). If I insert a dress makers pin in beside the zprobe signal pin and short the diode, the voltage at the pin toggles between +0.7 volts and +24 volts with respect to Ground. With the diode in circuit, the signal voltage toggles between approx +1 and +2 volts. It never goes to zero. However, if I unplug the probe at the zprobe socket and jumper the signal pin to Ground (the adjacent pin), I get the same results running command M119 i.e. 'z probe at min stop'.
Late Extra: I just tried it after re-plugging the z probe plug on the Duet board and presto, it's working properly! I've wriggled all the connectors but can't make it fail now. Thanks for walking me through this mysterious problem. I can now proceed to the stepper motors. Cheers, Ralph
