At the end, I was left with a totally disconnected Mega 2560 ( all wires are on male header pins, so were physically removed ) and still no change.
So I suspected the Arduino and ethernet shield.
Removed the shield - no change.
Disconnected the Mega and connected a spare, brand new, Mega - same reading - so unlikely that the Mega was damaged and causing the drain.
Disconnected the Mega and connected a spare, brand new, Mega - same reading - so unlikely that the Mega was damaged and causing the drain
This is where your logic slipped, you have everything disconnected and output still 9V, so supply is U/S.
Tom........ 