I bought a NAD 3300 Power Envelope (what's that?) integrated amp yesterday for $10 bucks. The unit will not switch off completely. When depressing the power switch, the amplifier part disengages (kills the sound output) but the LED's remain lit and I can still hear a slight electric hum.
Anybody have any ideas what might be the root of this evil? Faulty switch? Relay?

I have a few extra swiches around I could pop into it.

The thing works great, except for the fact it is perpetually on, requiring me to use a wall switch or unplug the unit.

Any help appreciated.