The tuner box for my Hitachi 42PD3000 makes a faint beeping noise when the set is switched off from the display. When the display is switched off using the standby button on the remote, the tuner box makes a faint, continuous and high pitch humming noise. You need to get close to the tuner box to hear these noises. I've had the tuner box replaced based on a Hitachi engineer's diagnosis that an alternator?? was loose but the noises persist on the new tuner box also. Other than that, everything is fine re. picture quality, sound, etc. Anyone else notice the same and what the source for these noises might be? Is it worth worrying about?