If its humming when its plugged in but not powered up. It is reasonable to conclude that its an AC issue (ground loop). That doesnt rule out defective internals of course.
Do you have cable (video) running into or through this system? If so, unplug it and see what happens.
You say you tried grounding the unit. Without checking any manuals (meaning I could be wrong) did you tie your components together via the chassis'? Off the top of my head, I think thats how it should be done. I'll look it up later or maybe a fellow A'goner who knows can help us with this one. Right now I am making a pot of chili so I can't dig out the manuals just yet.
Dont worry about tube hiss. Unless you have a bad tube, it is so low that you have to turn the volume up well past any reasonable level just to hear it. If you had a CD playing while it was turned up you would probably be well into audible distortion or even speaker damage volume levels.
Do you have cable (video) running into or through this system? If so, unplug it and see what happens.
You say you tried grounding the unit. Without checking any manuals (meaning I could be wrong) did you tie your components together via the chassis'? Off the top of my head, I think thats how it should be done. I'll look it up later or maybe a fellow A'goner who knows can help us with this one. Right now I am making a pot of chili so I can't dig out the manuals just yet.
Dont worry about tube hiss. Unless you have a bad tube, it is so low that you have to turn the volume up well past any reasonable level just to hear it. If you had a CD playing while it was turned up you would probably be well into audible distortion or even speaker damage volume levels.