If you have to ask a question like this then you should not even be thinking about working inside the microwave cabinet. Like Tim said there is dangerously high voltages in there even long after you pull the plug from the wall. Take it to an expert. 20 amp fuses don't just blow for no reason. There will be other problems causing it to blow.
Lincoln Appliance NZ
January 2014
please don't go inside the microwave as DANGEROUS high voltages present.Touch wrong bit you DIE!!!!
Tim
December 2013
Automatic Answer
While you wait for answers, we may have found some information which could help you.