Linn Lingo rattling sound....

My Lingo has a rattling sound coming from back end of the unit. I've opened it up and can't see anything loose. Sounds like it's coming from around the power input. Anyone have any ideas? Is this normal??? Tbh, I haven't used this for quite a long time so can't say if it's always been this way or not.

Any input is greatly appreciated. 

Thanks.