On the back of the core component, below the cooling fins, is a master power switch, next to which reads 'Replace only with same size fuse 4A 250v slo-blo'. The master power switch is housed in a threaded casing, secured by a thumbnut. It appears, as it did at the time of purchase, that if one were to remove the thumbnut, the fuse would be exposed for replacement. Nope, took of the nut, switch didn't even budge. Twenty wood screws and some elbow grease later revealed that the fuse is actually in the center of the unit, and that the fuse in not, as stated, a 4A 250v, but in fact a T4AL 250v, which appears very hard to find. Searching Gooogle returns only 4 mentions of this type of fuse.