This post is regarding an iMac 27" mid-2010, for your reference. I've noticed a ticking sound at one second intervals coming from inside my iMac when it is switched off but the plug is switched on at the socket. The noise doesn't occur in other instances. It doesn't matter whether it has been on for a while or whether it has been sat cold for a few hours. Is there meant to be some sort of analogue timer in there or did a watch get dropped in during production ? Anyone else have this? Thanks.