@dc42 Thank you for your quick response and your advice - it's really appreciated
As you se it turned out to be an end-switch board causing the problem .

@kb58 Thanks for your simple, yet brilliant, advice!
Pulled out everything, and the board worked fine. Put back one plug at the time and tested ..... and there it was - the X-Stop
Turned out to be the small end-switchboard with only a couple of resistors and caps. Replaced the board and everything works perfectly

The board is bauht on ebay, and is most likely a clone i'm affraid. .... and probably with low-quality components.
It has been working perfectly for about a year.
It's all the same when powered via USB.

I experience a 3.3v failure on my Duet2 wifi (v1.04)
There is no light in the +3v LED, and when measuring the voltage on a 3.3v pin it shows only about 0.5v.

The failure is however (for me) a bit strange. The board might start up normally, but after short time use it freezes and the 3.3v drops. (down to about 0.5v).

I suspect the 5v to 3.3v regulator (U2) being the "problem-child" ... but I'm not shure.

In a desperate attemt to come around the problem, I tried to supply 3.3v from an external source (via one of the 3.3v pins) - but the effect is the same. The voltage is drawn down to about 0.5v. So someting is shorting - with some resistance - to GND.

Has anyone experienced similar failure?