How do you open a 12v transformer to change the fuse?

To open a 12V transformer for fuse replacement, first ensure it is unplugged from the power source to avoid electric shock. Use a screwdriver to remove any screws holding the casing together, and gently pry it open. Locate the blown fuse, carefully remove it, and replace it with a new one of the same rating. Once replaced, reassemble the transformer securely before plugging it back in.