I didn't what to take any chances,
I've tried the power supply in other houses and it does the same so it's prob the transformer, although it's a buzzing sound not like the trans vibrating.
It was a present so i didn't what to have to get them to bring it back for me.Besides the store seem to run out of them very quick so i'd prob be the same time waiting on a new unit.
And of course i'd loose my created mii's then.
I posted it off on monday so sound have the new back shortly.
Cheers for the replys