Yes... the 12v barrel is powering the Mega. I don't have any room left for yet 'another' 5v PSU (already fitted 5).
But... that 12v barrel is only powering the Mega and a JQ8400 MP3 module.... nothing else.
There is no load on any of the pins (LED wise). Why is the jack so bad? Made MANY projects over the years using the 12v jack. If it's that useless, why fit it?
I drew a schematic, but then radically changed all the wiring... so sitting here now re-doing it.
It's weird. For some reason, plugging in the USB lead is not recognised (therefore I can't use the debug serial) unless I unplug the power to the project first, find the USB connection, and then re-power the device. What would cause that kind of interferrence?
Update... for reasons I don't yet understand, the regulator on the Mega is hot to the touch (took some internal parts removal to reach it).
So... Buck converter number 6 being installed