Same problem...don't you hate trying to explain the sound and behavior of it? I have taken mine apart originally planning on changing out the two 100mPf 35 volt capacitors on the main board since this is a common cause of the 'hum' problem according to most. Although in taking mine apart I found I also have a bad component which is burned up and I have no idea of what it was. Its labeled U502 and my guess is it was a capacitor...Anyone know for sure? (Guessing C29 0.1 u)
I am thinking that may be a secondary problem though and was only related to one channel not working. I think the hissing/buzzing/crackling is still related to those two capacitors. The suggestion is use caps rated at 105C instead of the 85C that are in there...