From what I've read, JAP SNES requires 9V DC whereas UK SNES will take 9V AC. Is it possible to fit a simple full wave rectifier (ie 4 diodes) and use a UK PSU on a JPN SNES?
You also could get a Sega power supply, they work with the Super Famicom. They look like this, be sure the polarity matches:
9V is pretty useless, so it's likely converting it to 5v inside anyway. It's possible that it can cope with DC or AC, but I wouldn't personally risk it without doing some more investigation.
There is obviously something strange going on there - the output connector on the UK version of the NES/SNES PSU has a larger outside diameter than the one on a US SNES or a Super Famicom and won't even fit.
Ah, that's a bummer. My plan was to just cut a few traces and chuck in a couple of diodes, didn't realise that the plugs were of different diameter. I'll just grab a DC PSU instead.