The barrel is 5.5mm, but the tip is
2.5mm.
I tried hooking it up to a Mission Engineering 529M, which has a single 9v out rated at 3amps (3000ma), same as the wall wart. When I turned it on, all I got was a white screen, even when I ran it straight from an outlet instead of the charging brick. Anyone else had success with this? I'd like to compare nores