Hi Thomas,
Do you think it is the power supply or could it be the fan? They are separate inside the Central...

Otherwise if it is the power supply, maybe something like the power transformer, that should be easily replaced...

I've never heard any noise coming from my units....

Thanks,
Randy
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Happy owner of 2 Centrals, 2 Empegs Mk2a 160GB, 1 Empeg Mk2a 60 GB, a Rio Riot, 4 Rio Receivers, and two 1GB iPod Shuffles...