Before replacing the fuse, remove the metal rear panel and test all the parts on it’s back with a magnet. You will be surprised to find that Magnepan uses ferrous (steel!) parts. I found steel parts in both the fuse holder and the Magnepan speaker hook-up connectors. That imo is a much bigger deal than the fuse itself.
I disconnected the fuse holder---bypassing it, and replaced the Magnepan connectors with Cardas binding posts, which fit into the stock holes without modification. Maggie old-timers have done both for many years.