Allnic H-3000 hum when mute button engaged.

Check grounding of the switch inside the unit.  It sounds like engaging the switch causes the Allnic to lose contact with ground.  It should be a simple fix.

Thanks Lewm.
I am finding the way to get access to the inside. Do you know it from the front or from the bottom of the unit?
Calvin

No
I've never been near an h3000
you need a pro

Return it and get your money back! 

Sorry for the brevity of my first response to your question about how to open up the case of the H3000. I was typing on my iPhone. I have no idea of your level of knowledge and experience when it comes to working on audio equipment, so that response was based on an assumption that you are not, in fact, experienced. You’ve got a very expensive, very fine piece of gear there. I would not advise you to service it yourself. If, however, you know what you’re doing, you probably by now have figured out how to open the case. Let’s assume that you do find a problem that is as obvious as a loose, unconnected wire. Would you know how to solder it back into place and what it should connect to? If the answers to those two questions are not yes and yes, it would be worthwhile to find a competent tech.

By the way, in my experience, problems like this rarely are as obvious as as a "loose wire". A bad ground could be caused by a cold solder joint that may look fine by inspection.

I don’t agree with Yogiboy, by the way.