Rockerverb 100 mk1 Mains fuse

[whiterabbit13]

My amp has been sitting unused for about a year. It was unplugged, covered, and in a climate controlled room. I went to power it up last night and the mains fuse blew within less than a second. Any ideas why? Furthermore does anyone know the Mercury Magnetics part number for the replacement power transformer in case that is the issue?