Hi Neuman, pictures will tell the story but black comb could just be a sign of an old hive. If you can see white grey larval mummies out the front of the hive and also in the cells of the comb then you more than likely have chalkbrood or stonebrood. If its AFB or EFB, this is a different story and its very important to diagnose the difference. If you think it could be AFB or EFB then a match stick to puncture a capped cell and swirl the stick in the cell and draw out the match to see if there is ropiness. Get back to us when you have had a good look.
http://forum.honeyflow.com/t/bee-diseases-and-pests-a-summary/1570