Hi Geoff,
My QMX does the same thing.? The story with mine is that initially there was a short on between the fets on the plug in regulator board.? I fixed this short by heating up the fet and sliding it sideways.??
Unfortunately, while fixing the short I created a solder bridge on the regulator board between two very close tracks.??
I found the short after a quick power up but the damage was done.
The short damaged a port on the processor which controls the power off process.?
So while the QMX powers up by the pushbutton, it now won't power down.? I've decided to live with it the way it is now as replacing the processor would be a big job (if I could obtain one!).
Cheers,
Glenn VK3YY.
Glenn S