I get a hum in my speakers on my Harman Kardon AVR110 when I first turn it on. It is a very annoying hum. It goes away after about 30-40 mins. If I turn it off and back on, the hum returns.
Does anybody have any ideas to resolve this issue?
Hum noises which slowly disappear as the unit warms are typically the result of defective power supply or possibly coupling capacitors. Hum in both channels suggests a power supply problem. Hum in only one channel would normally result from a coupling cap in that channel's circuitry. Take the unit to a repair shop and ask for an estimate of cost before you decide what to do.